The Yucca Moth 
AND 
Yucca Pollination. 
By CHARLES V. RILEY. 
(From the Third Annual Report of the Missouri Botanical Garden.) 
JSSUED MAY 28, 1892. THE YUCCA MOTH AND YUCCA POLLINATION. 
BY C. V. RILEY, PH. D. 
PART I. 
Introductory. 
Twenty years have nearly passed since the first an- 
nouncement of the method of pollination of our Yuccas by 
the little white Lepidopteron which I christened Pronuba 
yuccasella. The curious facts connected with its structure 
and life habits and its intimate relation with the Yuccas; 
the ease with which it is confounded with the Bogus Yucca 
Moth, found in the same flowers, but possessing no power 
of pollination ; the confusion which the facts have caused 
in the minds of other observers ; the criticism and discussion 
which have followed the observations; and the opinions of 
others, often based on erroneous observations and conclu- 
sions- have resulted in a number of articles, scattered 
through a number of publications. My friend, Professor 
Trelease, has repeatedly urged me to put together a con- 
secutive statement of the facts in the case, feeling that 
such a statement would prove useful to botanists and 
entomologists alike. It would seem, indeed, eminently 
appropriate to publish such a recapitulation in the Annual 
Report of the Missouri Botanical Garden, in which, while 
its founder was still living, many of the original observa- 
tions, both by Engelmann and myself, were made. 
The present article will fall, naturally, into two parts, 
the first a more popular recapitulation of the facts in re- 
ference to Pronuba yuccasella and Yucca pollination, in 
which will be repeated, almost verbatim, the earlier accounts 
as given in the third volume of the Transactions of the St. 
Louis Academy of Sciences and in my Fifth and Sixth 
Reports on the insects of Missouri, and elsewhere. In the 
99 100 
MISSOURI BOTANICAL GARDEN. 
second portion will be transcribed from my notes some un- 
published details not only in reference to this particular 
species but to other species of the family Prodoxidse to 
which it belongs. 
FERTILIZATION OF PLANTS GENERALLY. 
The common belief, based upon the theological assump- 
tion that all things upon this terrestrial sphere are for 
man's especial benefit, was, and perhaps yet is, that flowers 
were endowed with beauty and fragrance for our particular 
pleasure. Let us look somewhat more closely into this 
matter, and see what modern science has to say about it. 
Ever since Linnaeus used the sexual characteristics of 
flowers in classification, and Erasmus Darwin sang of the 
loves of the plants, the philosophy of fertilization in the 
plant kingdom has been fairly apprehended. It has long 
been recognized that plants are divisible into homomorphic 
or self-fertilisable, and heteromorphic or cross-fertilisable 
species. All diclinous plants, or those having separate 
male and female flowers, belong to the latter category, 
which is further classifiable according to the means by 
which cross-fertilization is effected. One class (termed 
anemophihe) depend almost entirely on the wind, and in 
these, of which our pines and other conifers, our pop- 
lars, willows, grasses, etc., are examples, the pollen or male 
element obtains in enormous quantities, is easily detached, 
and is generally produced early in spring, when winds pre- 
vail, and frequently before the development of the leaves, 
which would tend to impede its dispersion. The flower is 
inconspicuous and the stigma or female organ generally 
branched or hairy, so as to increase the chance of catching 
the wind-borne pollen. Water is an agency in the fertili- 
zation of a few plants, of which the singular Vallisneria is 
a striking illustration; while a few are aided by birds and 
higher animals ; but by far the greater number are ferti- 
lized, or more strictly speaking, pollinized, by insects. YUCCA MOTH AND YUCCA POLLINATION. 
101 
The most casual observer of nature must have appreci- 
ated, years ago, the fact that flowers are very important to 
insects, furnishing the essentials of life to those of several 
orders and especially to the Hymenoptera (Bees, Wasps, 
etc.) and Lepidoptera (Butterflies and Moths) in the form 
either of pollen or nectar. But that insects could be of 
any especial benefit to plants has only come to be acknowl- 
edged and fully appreciated of late years. Toward the 
close of the last century Christian Konrad Sprengel pub- 
lished an important work - Das Entdeckte Geheimniss der 
Natur - in which he maintained that the color, form, odor, 
secretions, and the general structure of flowers had refer- 
ence to insects which are essential as pollinizers. The 
importance of insects as agents in cross-fertilization was 
scarcely appreciated, however, until the late Charles Dar- 
win published the results of his researches on Primula, 
Linum, Lythrum, etc., and his elaborate work on the fer- 
tilization of orchids. The publication of these works gave 
to flowers a new significance and to their study almost as 
great an impulse as did his immortal " Origin of Spe- 
cies " to the general study of biology. Hooker, Bennett, 
Axell, Delpino, Hildebrand, Hermann Muller, and others 
abroad, and Dr. Gray and Mr. William Trelease in this 
country, have followed up this subject; and no one can 
familiarize himself with the results of their studies with- 
out a keen sense - if not a conviction - that in the vast 
number of cases Sprengel's early statement holds strictly 
true. By these deeper insights into the significances of the 
floral world, and their harmonies with the insect world, we 
learn to understand why night-blooming flowers are usu- 
ally white, even where their day-blooming allies are brightly 
colored, as in the case of Lychnis vespertina and L. 
diurna; or why the calyx, which is usually hidden and 
green, becomes bright when exposed, as in the Berberry 
and Larkspur. Many flowers are known to close or 
" sleep," and while most of them follow the animal world 
in taking this rest at night, yet there are marked excep- 102 
MISSOURI BOTANICAL GARDEN. 
tions. The dandelion goes to rest at 5 p. m., and wakes 
at 7 a. m., while the popular names of " 4 o'clock " and 
" John-go-to-bed-at-noon " sufficiently indicate the sleep- 
ing hours of Mirabilis and Tragopogon. Sir John Lubbock 
tritely asks " What is the meaning of sleep in flowers, if 
it is not in reference to insects?" The closing during 
those hours when the particular insects needed for pollina- 
tion are at rest, would protect the flower from spoliation 
by useless raiders. This belief is also strengthened by the 
fact that anemophilous flowers of those fertilized by the 
wind, never sleep, and that flowers which attract insects by 
smell, emit their odor at particular hours. 
But the most interesting fact not commonly understood, 
that has now been very fully established by the most 
thorough researches, is, that a very large number of plants, 
even where the sexes are united in the same flower, abso- 
lutely depend on insect aid for pollination, and that the 
contrivances to induce cross-fertilization are infinite in di- 
versity, while the modifications in structure which these 
insects have undergone the better to fit them to perform 
this service, are equally remarkable. 
In Dr. Asa Gray's little work, " How Plants Behave," etc., 
instances enough are given, in an admirably plain and lucid 
style, to show the manner in which many flowers are cu- 
riously and elaborately constructed so as just not to do of 
themselves what must necessarily be done for them in order 
to prevent degeneracy or extinction of the species. Some 
plants, as Fritz Miiller proved, are so self-impotent that 
they never produce a single seed by aid of their own pollen, 
but must be fertilized by that of a supposed distinct 
species, or even of a supposed distinct genus; while in 
some cases the pollen and stigma mutually act on each 
other in a deleterious manner. In most of these entomo- 
philous plants fructification may be brought about by the 
aid of more than one species of insects, and few plants 
offer a more striking instance of dependence or more cu- 
rious floral mechanism to allure, than do the orchids. In YUCCA MOTH AND YUCCA POLLINATION. 
103 
the genus Habenaria, for instance, we find flowers which 
in some cases strongly resemble butterflies; a separate 
pocket for the nectar; the pollen bound together in masses 
by elastic threads, so as to lessen the chance of loss ; the 
base of the stamens forming flattened sticky discs placed 
in the best possible position for adhering to the head-parts 
of a moth endeavoring to reach the nectar. In all these 
features and others that might be mentioned, there is 
remarkable adaptation; and the flowers of many orchids, 
as they unfold, seem not only to invite but to court and 
crave the intervention of some scaly-winged marriage-priest 
44 of glorious color and glistening eye," who shall at once 
procure a suitor and perform the nuptials. Yet here we 
have the adaptation of the plant only, and except in a few 
instances, as, for instance, in that Madagascar orchid, 
Angraecum sesquipedale, where the nectary is so deep that 
its nectar can be reached only by a moth (like Macrosila 
cluentius) with a very long tongue, our orchids are not 
dependent for pollination on any one Lepidopterous species, 
but may be aided by many which have tongues of sufficient 
length. 
CONNECTION OF YUCCA AND PRONUBA. 
There are, in fact, few plants which are dependent on a 
single species for pollination. So far as I know, the 
Yuccas furnish the only instance of this kind, for they 
actually depend on some particular species of little white 
moths belonging to the Tineiua and to the genus Pronuba. 
The Yuccas are a very interesting genus of lily-like plants, so 
familiar to everyone in our public and private gardens that 
I need not say very much about them. There are numerous 
species and even sub-genera, but they are all characterized 
by anthers not reaching anywhere near the stigma, so that 
fertilization unaided can take place only by the merest 
accident. In other words, the stigmatic tube is nowhere 
within reach of the stamens, and the pollen either remains 
attached to the open and withered anthers or falls and 104 
MISSOURI BOTANICAL GARDEN. 
remains in different sized lumps on the inside of the per- 
ianth, and cannot be introduced into the stigmatic tube 
without artificial aid. 
Our commoner garden Yuccas, forms of filamentosa, 
depend on the commoner Yucca moth, Pronuba yuccasella 
(Pl. 34, Fig. 1, b. c.) and so do all the different species 
found east of the Rocky Mountains, so far as we yet know. 
During the day-time we may, by knowing what and where 
to seek, often find this moth either singly or in pairs, 
resting with folded wings within the half-closed flowers. 
It is then not only hidden from ordinary view, but well 
protected by the imitative color of the front wings with that 
of the flower, so that close scrutiny is necessary for its 
detection. If we visit the plant after 
" * * * the garish clay 
Has sped on his wheels of light away " 
and when, with full-blown perianth, the Yucca stands in 
all her queenly beauty, and sends forth her perfume more 
strongly upon the night air, we shall, with a little patience, 
meet with this same moth, flitting swiftly from flower to 
flower and from plant to plant-the dusky nature of the 
hind wings and of the undersurface of the front wings almost 
completely offsetting and neutralizing, when in motion, 
the upper silvery whiteness of the latter, and thus still 
rendering the insect a little difficult of detection. It is 
principally the male which we thus see flying and, by the 
aid of a " bull's eye," we shall find the female for the most 
part busily at work in the flowers. He, with relatively 
stronger wing-power, can afford to spend in the most pleas- 
urable way the few brief days allotted to him; but she is 
charged with a double duty and loses little time in its per- 
formance. As a part of the maternal task of continuing 
her race, she must act as foster-mother to the plant in 
order to ensure a proper supply of food to her larvae, 
which, as we shall presently see, feed on its seeds. 105 
YUCCA MOTH AND YUCCA POLLINATION. 
STRUCTURAL CHARACTERISTICS OF PRONUBA. 
As preliminary to a better understanding of the habits of 
the female, it will be well to draw attention to those 
structural peculiarities which distinguish her from all other 
species of her order and which so admirably fit her for the 
work she has to do. PL 34, Fig. 3 gives some details of the 
head ( a) and an important structure which more particularly 
characterizes her and interests us, is the maxillary tentacle 
shown with its palpus at 6. She has a pair of these organs, 
which are prehensile and spinous, and it is chiefly by means 
of these that she is able to collect and hold a relatively large 
load of pollen for the purpose of pollination. Another 
organ which is characteristic is the ovipositor. When 
this is entirely withdrawn, the tip of the abdomen presents 
a truncate appearance, the terminal joint being bluntly 
rounded at the tip with a slight projection both above 
and below and with a corrugated ridge dorsally a lit- 
tle in advance of the tip. This terminal joint is very 
much compressed from the sides, with a few stiff hairs 
around the terminal border. The ovipositor issues from 
the middle of the truncate end and when critically exam- 
ined the basal part, when highly magnified, shows an im- 
bricato-granulate surface, the granulations strongest basally 
and diminishing distally, while the terminal part is smooth, 
long, and peculiarly constructed at the tip, the extreme tip 
being notched or serrate and having a dorsal fin also finely 
and sharply serrate, running anteriorly from it-the whole 
recalling in form the caudal and second dorsal fins of the 
Lamprey (Petromyzon). It thus presents itself, as usu- 
ally exserted when the moth is quickly killed while in 
the act of oviposition; the imbricate basal and smooth 
terminal parts looking like two joints, while the protruded 
portion of the vagina looks like a third and short basal joint. 
The various details shown in Plate 37, Fig. 1 will help to elu- 
cidate the nature of this organ. Ventrally along the ter- 
minal part is seen a membranous duct which broadens just 106 
MISSOURI BOTANICAL GARDEN. 
in front of the tip and has an outlet from which a soft, 
extensile oviduct can be extruded. This is fine, silk-like, 
pale, membranous and very elastic. It is smooth basally 
but armed along its terminal third with retrorse hairs, in- 
creasing somewhat in number and strength toward the tip, 
around which they are almost spinous. At first sight these 
would seem to be out of place and to impede rather than 
aid the insertion of such a delicate filament; but as we 
shall presently see the act of oviposition is a most intricate 
and difficult one and these hairs are doubtless sensitive and 
tactile and serve the double purpose of enabling the moth 
to feel her way in the ovarian cell and of temporarily 
anchoring in the soft wall thereof, while the egg is being 
passed to its destination. The manner in which this re- 
markable ovipositor is worked by chitinous rods with 
muscle attachments will be considered in a fuller statement 
of the internal anatomy of the moth in the second part of 
this paper. My purpose here is to call attention simply to 
those features which will more fully explain her visible 
acts, and it will be seen that this ovipositor is admirably 
adapted for cleaving through the young fruit and then 
running the egg into the ovarian cavity, as will be pres- 
ently described. The male has no very marked character- 
istics and is distinguished from allied species chiefly by 
the structure of the exposed horny parts of the genitalia 
at the tip of the body. (Pl. 37, r. s.). 
Though all the acts of the female are nocturnal, it is not 
at all difficult to follow them with a lantern, for, albeit 
ordinarily shy, she may be closely approached when she 
is about to oviposit. Her activity begins soon after dark, 
but consists, at first, in assiduously collecting a load of 
pollen. She may be seen running up to the top of one of 
the stamens, and bending her head down over the anther, 
stretching the maxillary tentacles, so wonderfully modified 
for the purpose, to their fullest extent, the tongue uncoiled 
THE ACTS OF POLLINATION AND OVIPOSITION. YUCCA MOTH AND YUCCA POLLINATION. 
107 
and reaching to the opposite side of the stamen. In 
this manner she is able to obtain a firm hold of the stamen 
while the head is kept close to the anther and moved pe- 
culiarly back and forth, something as in the motion of the 
head of a caterpillar when feeding. (Pl. 38, Fig. 2.). The 
maxillary palpi are used in this act very much as the or- 
dinary mandibles are used in other insects, removing or 
scraping the pollen from the anthers toward the tentacles. 
After thus gathering the pollen, she raises her head and com- 
mences to shape it into a little mass or pellet by using her 
front legs very much as a cat does when cleansing her 
mouth, sometimes using only one leg, at another time both, 
smoothing and pressing the gathered pollen, the tentacles 
meanwhile stretching and curving. After collecting all 
the pollen from one anther, she proceeds to another and 
repeats the operation, then to a third and fourth, after 
which, with her relatively large load - often thrice as large 
as the head - held firmly against the neck and front tro- 
chanters, she usually runs about or flies to another plant; 
for I have often noticed that oviposition, as a rule, is ac- 
complished in some other flower than that from which the 
pollen was gathered, and that cross-fertilization is thus 
secured. 
Once fully equipped with this important commodity, 
she may be seen either crawling over or resting within 
the flower, generally with the head toward the base. From 
time to time she makes a sudden dart and deftly runs 
around the stamens, and anon takes a position with the 
body between and the legs straddling two of them, her head 
being usually turned toward the stigma. As the terminal 
halves of the stamens are always more or less recurved, 
she generally has to retreat between two of them until the 
tip of her abdomen can reach the pistil. (Pl. 37, Fig. 2). 
As soon as a favorable point is reached, generally just below 
the middle, she rests motionless for a short time, when the 
abdomen is slightly raised and the lance-like ovipositor is 
thrust into the soft tissue, held there the best part of a 108 
MISSOURI BOTANICAL GARDEN. 
minute, while the egg is conducted to its destination, and 
then withdrawn by a series of up and down motions. 
In non-technical language, the pistil or the young fruit, 
below the stigmatic tube, shows externally at this time six 
quite distinct longitudinal divisions each having a median 
ridge, there being six corresponding depressions or con- 
cavities in which the six stamens fit, especially at the base. 
Technically, the pistil is a three-celled ovary, the styles bifid 
at tip and united so as to form the stigmatic tube. A 
transverse section anywhere about the middle will show 
that each of the six longitudinal sections contains a row of 
ovules within the ovarian cell. More strictly, the ovules 
are in pairs, as there are but three primary sections or 
carpels, divided by three primary divisions or dissepiments. 
Pl. 36, Fig. 1, shows a transverse section of one of these 
primary divisions or carpels which well indicates the posi- 
tion of the ovule (a) the funiculus (5), the placenta (c), 
and the ovarian cell (d). As the fruit enlarges the three 
secondary dissepiments narrow and coalesce, while the other 
three widen, so that the pod becomes practically three-lobed 
and the seeds are more distinctly in pairs, the inner side 
straight and the external quite convex. In oviposition the 
young fruit is pierced just within the ridge in the depres- 
sion occupied by the stamens, and almost always on the 
side of one of the primary or deeper divisions, where the 
walls are thinnest, so that the ovipositor enters the ovarian 
cell at the external or rounded side of an ovule, and does 
not ordinarily touch the ovule itself. (Pl. 36, Fig. 2, aa). 
Rarely, however, the ovipositor penetrates the ridge and 
passes between two of the ovules, or sometimes even pene- 
trates one, this last case being, however, quite exceptional. 
During the insertion of the egg, which, as stated, usually 
occupies about one minute, a nervous twisting and tremb- 
ling of the body may be observed, and so intent is the moth 
upon this work that after the ovipositor once penetrates the 
pistil, the whole perigon may be detached, some of the 
encumbering stamens and petals removed, and the insect YUCCA MOTH AND YUCCA POLLINATION. 
109 
brought within the range of a good lens, when all her move- 
ments may be observed to the greatest advantage without 
disturbing her. In this way I have been able to watch the 
consignment of hundreds of eggs, and to admire the delicacy 
and elasticity of the oviduct proper, which issues from the 
chitinous sheath in a silk-like thread, almost invisible to 
the naked eye. While being withdrawn it is seen to be as 
long as, or longer than, the terminal abdominal joint and 
stretches or bends as the body is raised or lowered, in 
freeing it from the pistil. Indeed this freeing is a laborious 
job, and occupies from forty seconds to two minutes. 
Oviposition rarely begins before dusk, and takes place 
only in the flowers which are newly opened, i. e., during the 
first or second nights after opening, as it is chiefly during 
these nights that the ovary is susceptible to pollination, the 
stigmatic tube and the ovules, which are at first open for 
the reception of the pollen, thereafter closing. The moth 
seems instinctively aware of this and is never found ovi- 
positing in the older flowers. Indeed, her actions indicate 
that she investigates closely not only the condition of the 
pistil as to development, but as to whether or not it has 
already been punctured. 
It may be well here, in order to more fully understand 
the action and influence of the moth, to look a little more 
closely into the characteristics of the Yucca flower at this 
stage of its development. A longitudinal section of the 
upper portion of the pistil will show us the style with its 
stigmatic tube, which, at this time, communicates with the 
ovarian cells. Trelease (who will, I hope, accompany this 
article with some botanical details showing the pollen tubes 
and other microscopic structures) has shown that the stig- 
matic liquor is not nectarian, but that the slight amount 
of nectar which is associated with the flowers, is secreted in 
thin pockets formed by partitions that separate the three 
cells of the pistil and which open externally by a contracted 
pore from which the nectar is poured through a capillary 
tube (enclosed by the closely applied but not outwardly 110 
MISSOURI BOTANICAL GARDEN. 
united lobes of the ovary) to the base of the pistil, so that 
nectar-feeding insects seek it, not about the stigma, but at 
the base of the stigma or of the petals, whether within or 
without. I have fully verified Trelease's statements by 
dissection of the pistil and by study of the insects seeking 
this scant nectar and endorse his conclusions, that, while 
the observations serve to disprove any positive value of 
their nectar in the pollination of the Yucca flowers, they 
add to the importance of Pronuba by showing that the acts 
of collecting pollen and transferring it to the stigma do not 
result in any food compensation, as I was at first inclined 
to suppose. In other words, there is no nectar to allure 
other nectar-loving insects and cause them to go to the 
stigma; but on the contrary, those which are drawn to the 
plant by the slight amount of nectar are led in the very 
opposite direction, viz., to the base of the style or of the 
flower. It is also an interesting fact that I have never 
noticed Pronuba feeding, as contradistinguished from pol- 
linizing, for the motions of the tongue of Lepidoptera when 
feeding are quite characteristic and easily recognized. 
Indeed the two pieces which form the tongue are so often 
separated at tip, and so weakly joined throughout, as to 
raise the question, in connection with a somewhat imperfect 
alimentary canal, as to whether the moth feeds at all, and 
to suggest that the rather strong tongue, otherwise, assists 
pollination. 
No sooner is the ovipositor withdrawn into the abdomen 
than the moth runs up to the top of the pistil, thrusts the pol- 
len into the stigmatic opening, and works her head rapidly- 
the motion being mostly up and down and lasting several 
seconds. She works with a vigor that would indicate com- 
bined pleasure and purpose and makes every effort to force 
the pollen into the tube, thrusting it ordinarily from the 
base of one of the three primary clefts of the style. In 
my earlier observations I had always supposed that the 
tongue was used, in this operation, for sipping the liquid 
from the stigma after, or in connection with, her more YUCCA MOTH AND YUCCA POLLINATION. 
111 
arduous work; but it is probable that, seeing that this 
liquid is not nectarian, Professor Trelease is right in 
stating that the tongue is used to thrust the pollen further 
into the cavity than her tentacles can reach, though I 
can see no necessity for this action so far as pollination is 
concerned. After the more vigorous motions of thrusting 
the pollen into the tube, she frequently rests in comparative 
quiet, working her tongue in the tube sometimes for four 
or five minutes together, but ordinarily the act of pollina- 
tion ceases with the few vigorous thrusts already described. 
The importance of this act will be better appreciated when 
I state that numerous experiments in artificial or brush 
pollination have shown that effective fertilization in Yucca 
jilamentosa is by no means an easy matter, and that it 
rarely takes place as effectively as through the actions of 
Pronuba. 
This carrying of the pollen to the stigma generally fol- 
lows every act of oviposition, so that where ten or a dozen 
eggs are consigned to a single pistil, the stigma will be so 
many times be-pollened. The ends of the tentacles, which 
are most setose and spiny, and which are always curled 
into the pollen mass when not uncoiled, must necessarily 
carry a number of pollen grains into the stigmatic tube 
each time pollination takes place ; and I have noticed a 
gradual diminution in the size of the collected mass, corre- 
sponding to the work performed, which is indicated by the 
rubbed and worn appearance of the individual, the freshest 
specimens always having the largest loads. I have also 
noticed that where oviposition occurs thrice in the same 
pistil (and this is most common), the three corresponding 
acts of pollination are consecutively in the three deeper 
notches of the style, thus insuring a supply for the ovules 
in each carpel. Pollen collecting is, however, sometimes 
continued after oviposition has begun, but is rarely witnessed 
during the active period of egg-laying. This is, however, 
invariably followed by pollination, though not always alter- 
nating therewith. Indeed it is not uncommon for a female 112 
MISSOURI BOTANICAL GARDEN. 
to consign two or three eggs to the same pistil, before run- 
ning up to the stigma and inserting the pollen. 
While oviposition generally takes place in the manner 
described, the moth head outward (Pl. 37, Fig. 2) and 
straddling two stamens, the opposite position is sometimes 
assumed, and larvae and punctures are not infrequently 
found in the upper part of the fruit, especially where 
a single fruit is stocked with ten or more larvae. As 
the fruit enlarges, the mouth of the puncture forms a 
slight discolored depression, more noticeable in some 
varieties than in others; but the passage-way becomes 
obliterated. 
DEVELOPMENT OF THE EGG AND LARVA : TRANSFORMATIONS 
OF PRONUBA. 
The egg is an extremely delicate, thread-like structure, 
averaging 1.5 mm. in length and less than 0.1 mm. (Pl. 37, 
fig. 1, in diameter, tapering at the base and enlarg- 
ing slightly toward the capitate end, which has also a slightly 
indurated point. * It is impossible to follow it with the 
unaided eye or in fact with an ordinary lens, even if 
the pistil be at once plucked and dissected; but by 
means of careful microscopic sections, we may trace 
its course. From the position assumed by the moth, 
the ovipositor punctures the pistil somewhat obliquely, 
but as the egg is much longer than the diameter of 
the ovarian cell, the delicate oviduct of the moth 
bends and then runs vertically along the inner part of the 
cell next the placenta, and leaves the egg extending in this 
longitudinal direction along some seven or eight ovules, as 
* In the ovaries the less developed eggs are shorter and elliptical, as 
shown in my earlier figure (Proc. A. A. A. S. XXIX , Fig. 3, h.~) and 
there is every gradation between this and the more mature ova which 
have the same filiform character as when seen in the Yucca pistil. It is 
interesting thus to note that the immature and undeveloped egg of Pro- 
nuba corresponds with the mature egg of Prodoxus. YUCCA MOTH AND YUCCA POLLINATION. 
113 
shown in the illustrations (Pl. 35, Fig. 2, c. c. ).* The 
apical end of the egg soon enlarges (Pl. 37, Fig. 1, n) 
and the embryo may be seen developing in it, very 
much as in the case of the similarly elongate eggs of gall- 
flies (Cynipidse), though the pedicel does not shorten, 
as observed in these last. Segmentation is noticeable on 
the second day and the Yucca ovule at once begins to 
swell and enlarge, the irritation (doubtless mechanical) 
influencing the plant tissue much as in the case of the punc- 
tures of the gall-flies just mentioned. Sometimes two or 
more adjacent ovules are thus affected. 
The larva hatches in about a week and will be found at a 
point from 8 to 10 ovules above or below the external punc- 
ture according as the egg was thrust above or below it. It is 
not more than 1 mm. long and seems to live for some time on 
the juices of the degenerate and swollen ovules, but finally 
enters one that is developing, at the funicular base. So 
far as I have observed, the larva undergoes some three 
different molts, as but four different sizes of the head 
have been noticed. The general color, which is at first 
translucent white, conforms for the most part to the color 
of the tissues in which it is feeding; but becomes in time 
more yellowish, and finally, when mature, ordinarily ac- 
quires a rosy hue. The larva has no pro-legs, but has well- 
developed thoracic legs. It matures with the ripening of 
the seeds, which differs in time in the different species of 
Yucca, and also in the same species, but occupies on an 
average about a month in the ordinary Yucca filamentosa. 
The number of seeds destroyed is rarely more than a dozen 
and more frequently less, and I have recorded the fact of 
* The position and development of the egg were studied in 1874, by 
Engelmann and myself (Trans. Ac. Sc. St. Louis, III, pp. 208-211) and while 
the egg, from those observations, is sometimes curled around an ovule in 
the ovarian cell, the position above described is the normal position as 
subsequent study has shown. I also gave there the duration of the 
egg state as four or five days, but it more often extends beyond a week. 
I also there attributed the swelling of the ovules to the action of the 
larva, but it begins before this hatches. 
8 114 
MISSOURI BOTANICAL GARDEN. 
having found as many as twenty-one larvae in a single 
pod. Just about the time the pods are hardening and 
ready to dehisce and the seeds have already colored, the 
full-grown larva bores its way out of the pod, makes its way 
to the ground - in all probability by the aid of a silken 
thread - and there bores several inches below the surface 
and forms a tough silken cocoon intermixed with the soil. It 
makes its burrow to the extreme epidermis of the pod some- 
time before it leaves, and if there should happen to be a long 
spell of wet weather at this time, the burrow is very apt to 
become saturated with moisture and the larva to perish 
from mould. I have never seen one issuing during the 
day, or in the early part of the night, so that it probably 
leaves the pod late at night. It remains as a larva within 
its cocoon during the fall, winter and spring months and 
only transforms to the chrysalis state a few days before 
the blooming of the Yuccas. The chrysalis, (Pl. 34, Fig 4) 
as shown in the figure, is armed with an acute spine on the 
head and with singular spatulate spines on the back, which 
are well fitted to enable it to work its way to the surface 
from its underground retreat. 
It thus works its way partly out of the ground and as 
this is generally under the shelter of the mass of Yucca 
leaves (in the case of our filamentose species) the issuing 
is rarely seen, except by the most careful watching. The 
newly-escaped moth, with wings crumpled and moist, runs 
up one of the leaves and hangs thus sheltered, while her 
wings expand, following the invariable rule of all the mem- 
bers of her Order, and throwing them first back together 
to facilitate inflation (Plate 34, fig. 2) and only closing them 
and folding them along the body after they have become 
sufficiently firm. 
EFFECT OF PUNCTURE ON THE FRUIT. 
The effect of the puncture of the female moth in ovi- 
position is at once noticeable on the young fruit by a darker 
green discoloration externally. In time this becomes a YUCCA MOTH AND YUCCA POLLINATION. 
115 
depression, and the irregularities of the pods (Pl. 34, Fig. 
5, b. c.) which have been considered characteristic of the 
fruit of the genus are chiefly due to these punctures, which, 
ordinarily occurring just below the middle of the pod, 
produce a more or less marked constriction there. This I 
have often proved by artificially pollinizing the flowers 
and protecting them from Pronuba, when the pods will 
develop in a regular, parallel-sided manner (Pl. 34, Fig. 
5, a.) Internally the effect of the puncture is no less 
marked. A few of the ovules in the region of the punc- 
ture are at once affected, as already described, while the 
development of a yet larger number is more or less arrested, 
this being the case even when not touched by the ovipositor 
or the egg, or even where the egg fails to hatch. Did the 
ovules develop immediately around the egg it is probable 
that they would crush it. At Pl. 35, Fig. 2 d is shown a 
section of a carpel 7 days old with egg, and of another, e, 
with the larva just hatched. 
EFFECT OF FERTILIZATION ON THE STALK. 
It is an interesting fact that, however pollinized, whether 
by Pronuba or artificially, each Yucca panicle will mature 
but a certain number of pods, so that a number of those 
which are fructified drop after a few days' development, 
while some wither even after they have reached nearly full 
development. This gives an element of uncertainty to 
experiments and makes it necessary to be very careful. 
It is interesting also to note how the mere fact of fruc- 
tification influences the main stalk, at least in Y. filamen- 
tosa, for where a panicle is protected with gauze, so as to 
prevent the access of Pronuba, and cause the dropping of 
all the flowers, the stalk soon thereafter withers and dies. 
DATES OF THE FLOWERING OF THE YUCCAS AND APPEARANCE 
OF THE MOTH. 
There is some irregularity in the flowering of our Yuccas, 
even of those of the same species. The typical form of 116 
MISSOURI BOTANICAL GARDEN. 
Y. filamentosa at Washington and St. Louis begins bloom- 
ing about the middle of June, and is usually through 
blooming about the middle of July. In Philadelphia, so 
near to Washington, it blooms nearly two weeks later. 
Y. angustifolia blooms from a fortnight to three weeks 
earlier, so that it has almost ceased to bloom before fila- 
mentosa begins. Pronuba yuccasella is restricted in its 
appearance in the imago state, and in the eastern portion 
of the country appears coetaneously with the flowering of 
Yucca filamentosa, the males almost always being seen 
first. Thus both at St. Louis and at Washington 
Yucca angustifolia does not ordinarily set fruit, because 
it flowers before the Yucca moth appears. Occasionally, 
however, this last is about when some of the latest or 
terminal flowers are open, and I have known a few pods on 
the tip of the panicle of this species'to be fructified in St. 
Louis. So in the more northern States, where Yucca aloi- 
folia is cultivated, it blooms too late to be pollinized, and I 
have never known it to set fruit. 
In South Carolina, as Dr. J. H. Mellichamp informs me, 
there is even greater irregularity in the blooming of Y. fil- 
amentosa, though the genuine or more typical form blooms 
a month earlier than at Washington. This is pollinized 
by Pronuba; but some varieties bloom earlier or later - 
even in autumn. In these later bloomings Dr. Mellichamp 
has never known fruit to be produced. The variety laevi- 
gata usually blooms two weeks later, and the variety brac- 
teata still later than the typical form. 
Yucca aloifolia blooms in the south in June and July and 
the earlier blooming specimens are pollinized by Pronuba. 
Yucca gloriosa flowers in the south still later (September 
and October) and rarely sets fruit. It is very irregular, 
however, and on one occasion Dr. Mellichamp found a 
plant blooming in June in an old sandy field. This was 
the only plant he ever saw blooming in summer, and it 
produced fruit. I have seen a form of it blooming in 
March, with no sign of fructification. YUCCA MOTH AND YUCCA POLLINATION. 
117 
Further accurate and careful observations are very de- 
sirable as to the dates of appearance of Pronuba in the 
Gulf States region. The general result of my observations 
in the southern States as to the presence of the insect would 
indicate that its appearance is adapted there to the greater 
irregularity of the blooming of the Yuccas; but as a gen- 
eral thing, Y. aloifolia is seldom fructified except when 
blooming at the same time as filamentosa, and the same is 
true of gloriosa, which more rarely produces fruit. 
No one can observe our Yuccas closely without noticing 
a certain irregularity in blooming. The same root-clump 
of filamentosa will some years throw up several flower- 
stalks and in other years none. This is particularly no- 
ticeable in the Rocky Mountain region, and the fact that 
the flowers of Yucca brevifolia are uniformly scarce over 
large stretches of country has been repeatedly observed 
and reported to me. I observed it on my first visit to 
these tree Yuccas in 1887 and I remember very well that of 
Yucca angustifolia- which is quite common on approach- 
ing Denver and was found all along the Denver & Rio 
Grande R. R. to Colorado Springs, growing even in the 
side-walks of that town - not a single flower-stalk was 
noticed when I first visited those parts in 1873. This 
irregularity in blooming would prove fatal to insects de- 
pending upon the flower and fruit, were there not some 
provision to meet it, and it is one of the noticeable char- 
acteristics of the Yucca moths that they are equally irregu- 
lar in development; for, as we shall presently see, a very 
large percentage of the moths fail to issue the year follow- 
ing the development of the larva, but show a great tendency 
to retardation in development, some of them not issuing 
until the second, third or fourth year. This is equally true 
of both Pronuba and Prodoxus. 
NEED OF PRONUBA 
We have already seen that all the pods do not contain 
Pronuba larvse, though we rarely find any on the fila- 118 
MISSOURI BOTANICAL GARDEN. 
mentose species that do not show the marks of puncture, 
which indicates that a great many punctures are fruitless in 
result, owing either to the difficulty of the operation of 
oviposition, or to the fact that the eggs, having been once 
consigned to the pistil, have failed to hatch, for one reason 
or another ; or again, that the larva has, for one reason or 
another, perished. A similar mortality is connected with 
the similarly difficult and complicated oviposition of the 
Cynipidse, as Adler has shown. In dissecting the young 
fruits of the filamentose Yuccas, with a view to critical ex- 
amination, I have found that about half of them, on the aver- 
age, contain nothing; but the proportion varies greatly in dif- 
ferent localities and according to circumstances, and I may 
say that, as a result of my numerous examinations, fully 
two-thirds of the mature pods are found to contain the 
larvae of Pronuba. All the experiments which I have so 
far made, or have known to be made, prove conclusively 
that the capsular species never set fruit without her aid. 
SELF-FERTILIZATION OF YUCCA. 
While the capsular Yuccas are thus sterile wherever 
Pronuba does not occur, or is excluded from the flowers, 
there is good evidence that some of the soft-fruited species 
have exceptionally set fruit where there is every reason to 
suppose that Pronuba does not exist. I have already shown, 
in previous writings, how the structure of the flowers of 
dloifolia renders the chance of pollination greater than in the 
other cultivated forms. There is no style, the stigma is 
sessile, and the stigmatic liquor is abundant, filling, and even 
overflowing, the shallow opening or tube. The flowers are 
always more pendulous, oven in full expansion, than in the 
filamentose species and the stamens relatively longer, (Pl. 
35, Fig. 1), so that there is more likelihood of the pollen 
falling on the papillose apex of the stigma or being brought 
near it by conniving petals. In this connection I also 
introduce a figure to show certain variations and deformi- 
ties which sometimes occur in the pistil of Y. filamentosa YUCCA MOTH AND YUCCA POLLINATION. 
119 
(Pl. 38, Fig. 1) and which would suggest another possible 
method of self-pollination, namely, by the stamens reaching 
an exceptional length. So far as any proof is concerned, 
this has never happened with any of the filamentose species, 
and in any event must be of extremely rare occurrence. 
The mere accidental introduction of any of the pollen 
grains into the stigmatic liquor would in all probability 
serve to fertilize some of the ovules, though I doubt 
whether complete fructification could thus ensue. The 
stigmatic cavity varies very much in the amount of its 
secretion, which is sometimes abundant and at other times, 
almost or quite absent, and both Professor Trelease and 
myself have noticed that it is more abundant on Yucca 
angustifolia in its native habitat than on eastern grown 
plants. 
PRONUBA THE ONLY INSECT POLLINIZER. 
In my earlier studies, while the mutually beneficial 
adaptations of Pronuba and Yucca were at once apparent, 
I was strongly inclined to believe that there must be, 
occasionally, accidental pollination of the flowers by other 
insects, more particularly because of the fact just mentioned 
that the fleshy-fruited species were reported to occasion- 
ally produce seed in regions in which, presumably, the 
Yucca moth did not exist. I became interested, therefore, 
in carefully studying the habits of all insects found asso- 
ciated with or found within the flowers of Yucca. I have 
particularly watched and observed the Pennsylvania Soldier- 
beetle Pl. 38, Fig. 3), which 
is more commonly found within the flowers than any other, 
and which has a peculiar mouth structure which would lead 
one to suppose that it would have something to do in at- 
tempting to get at the stigmatic liquor. Without going 
into details, I may say that observations covering a 
period of nearly twenty years have only served to convince 
me of the incapacity in this respect of all other insects as- 
sociated with the plant. The Chauliognathus above men- 
tioned I have never found anywhere near the stigma. All 120 
MISSOURI BOTANICAL GARDEN. 
its movements show that it seeks what little nectar it can 
find at the base of the flower, which it uses however, chiefly 
as a place of shelter. It may and I think does feed 
somewhat on the fallen pollen, and in so far interferes 
with pollination by the moth. The beetle is almost 
always found in pairs, the female quite gravid, and 
while her eggs have not yet been described, and the 
place of oviposition is yet unknown, they are in all 
probability laid in the ground, and the larva is known to 
be predaceous and to be one of the enemies of the common 
Apple Worm. None of the other insects have ever been 
observed to go to the stigma and none of them have been 
observed to gather pollen. The few Hymenoptera, includ- 
ing the common Hive Bee, which are on rare occasions found 
about the flower, are accidental rather than habitual visi- 
tors, and get little satisfaction in the modicum of sweet 
they can find near the base of the flower. The slightly 
glutinous nature of the pollen, which is not easily dusted 
on to hairy insects, makes it extremely doubtful whether 
it is ever, even by accident, attached to the head of an in- 
sect that might by chance seek the stigmatic liquid, and 
the experiments I have made indicate that, with the long- 
styled Yuccas, a very thorough and effective insertion of 
the pollen grains is necessary for fertilization. These 
general conclusions have been confirmed by specific ex- 
periments made for the purpose; for over and over again 
I have excluded Pronuba by covering the whole panicle 
with gauze and have admitted all sorts of other insects in 
the hope of inducing fertilization; but in every case I have 
failed, whereas, whenever Pronuba has been admitted to 
the flowers, there has been evidence of her work and 
fructification. 
Pronuba yuccasella is found in all parts of the country 
east of the Rocky Mountains where the filamentose Yuccas 
normally range; but has not extended to all section s 
where they are cultivated. The time of its appearance, as 
we have seen, is strikingly coetaneous, east of the Missis- YUCCA MOTH AND YUCCA POLLINATION. 
121 
sippi, with the blooming of filamentosa ; while other culti- 
vated species which bloom either earlier or later, and which, 
therefore, do not receive the visits of the moth, I have as 
already stated, never known to bear seed. On the western 
plains, where Y. angustifolia is native, the moth's season of 
appearance is adapted to the flowering of this particular 
Yucca. In California, Yucca whipplei is pollinized by Pro- 
nuba maculata, an invariably maculate species ; while on the 
Mojave desert, Yucca brevifdlia is pollinized by Pronuba 
a species still more abnormal than yuccasella and 
modified to fit it to the peculiarities of that peculiar species 
of Yucca. In the Gulf States the typical yuccasella occurs, 
and fertilizes not only the filamentose Yuccas, but, as al- 
ready shown, those individuals of the larger, fleshy-fruited 
species like aloifolia which happen to bloom about the same 
time of the year. 
Thus we find that some species of Pronuba is connected 
with all the Yuccas, so far studied in this connection, and I 
have no doubt that this will be found to be generally true, 
so far as the indigenous species are concerned, and that in 
the native home of any of the species we shall find that 
pollination depends upon some species of Pronuba. This 
is rendered certain by the fact that wherever I have 
been able to examine the mature or partially mature fruit of 
other Yuccas in herbaria, I have in almost every instance 
observed the constriction and in most instances seen traces 
of the puncture and the work of the larva. A large and 
interesting form of Pronuba may be expected from the 
Giant Tree Yucca of northeastern Mexico ( Yucca filifera 
Chabaud), the palma of the Mexicans, with its enormous 
pendulous panicles from four to six feet long. The fruit 
is described as often constricted, a result doubtless of the 
work of Pronuba, and the only pod in the herbarium of the 
Department of Agriculture, shows this constriction. This 
baccate fruit is from 2 to 3 inches long and the stigma of 
the young fruit is farther removed from the anthers than 
in any other species. The long, thin, smooth and more 122 
MISSOURI BOTANICAL GARDEN. 
flaccid leaves of this tree Yucca permit much more easy 
study (with the aid of a ladder) of its flowers than of 
'Yucca brevifolia, with its stiff, sharp, serrate leaves, which 
form a veritable clievaux-de-frise. The small pod of Yucca 
rupicola from Texas, with its persistent beak-like style, 
also shows the work of Pronuba and is probably pollinized 
by a distinct species, as is also, doubtless, Yucca treculeana. 
I shall be delighted to receive any insects found in or con- 
nected with the flowers or fruit of any of the different 
species from Mexico and the south-west, or even ripe fruit, 
from any one into whose hands this paper may fall, and 
who has had an opportunity of studying the other species 
of Yucca which have not yet been studied in connection 
with pollination. 
I have often been struck with the power which the moth 
has of detecting isolated plants blooming for the first time 
remote from other plants or in localities where she could 
not possibly have been previously developed, a fact which 
indicates that, where abundant, in addition to her ordinary 
more sedentary duties, she takes long reconnoitering flights. 
GENERAL CONSIDERATIONS. 
The facts here set forth can be observed by any one who 
will take the trouble to assiduously investigate them. It 
has been a source of frequent pleasure to me to introduce 
my friends to this little moth and its curious ways, and al- 
most every one of my assistants, or those who have been 
associated with me, have been able to verify the facts 
repeatedly, while some of them have been of material aid 
in carrying on the observations ; for these observations are 
more satisfactorily made by two persons than by one, as it 
is difficult for one person to hold the lantern and at the 
same time closely investigate. I would here express my 
particular indebtedness to Messrs. L. O. Howard, E. A. 
Schwarz, Otto Lugger, Albert Koebele, C. L. Marlatt, and 
Th. Pergande, who have aided in the different experiments, 
particularly the latter, who helped me in the earlier ones 123 
YUCCA MOTH AND YUCCA POLLINATION. 
in St. Louis and whose interest and enthusiasm have never 
failed to produce good results in any special work he has 
done for me. 
In this connection I take pleasure in reproducing some 
experiences of Professor Trelease's, as communicated to me 
last July, not so much because they so fully confirm my 
own, as because they are in such refreshing contrast, in 
their accuracy and insight, to those of some others who 
have published on the subject. He writes: - 
" In addition to my observations noted in Bulletin Torrey Club, 1886, 
185, I have watched the moths at work in 1890 and 1891 - the only 
seasons when I have been at home during the blooming season - and 
have had my assistants, Duffey and Webber, make independent observa- 
tions and demonstrate pollination to our garden pupils. The observa- 
tions were made on Y. filamentosa, including its various forms cultivated 
in St. Louis under other names. Each act of oviposition is so promptly 
followed by pollination that the moth seems to have it on her mind to 
perform the latter as a sequel to the former, and I am disposed to think 
that my belief that either might occur first came from the first observa- 
tion in a given case happening to begin between the two acts. I have 
not positively confirmed my observations on the use of the tongue in 
pollination, though Webber feels certain that he has this year seen it 
so used. I do not, therefore, look on it as normal - and this would 
lessen the probability of the habit of thrusting pollen into the stigmatic 
chamber having been acquired while the moth was feeding on the stig- 
matic fluid. The latter varies much in quantity, and as you have stated, 
frequently fills the chamber, especially in the early morning. The septal 
glands are quite as inactive as I at first stated; but this year we have 
several times in the early morning found abundant watery fluid both 
within and outside the perianth, as noted by Meehan, but without ascer- 
taining its source. I am certain, however, from its position, that little 
if any comes from the glands. Before 9 a. m. we have several times this 
year seen a few hive bees gathering this fluid, both within the flower 
and from the outside, and I once saw a bee (Apis) probing, but appar- 
ently unsuccessfully and very hastily, the space between the bases of 
the filaments, and consequently the outlets of the nectar ducts. In ad- 
dition to my assistants and pupils I have shown the acts of oviposition 
and pollination to the Vice-President of our Board, to Coulter, Evans 
and several other visitors to the Garden, as well as to my wife and her 
sister. Every one who has seen the work done shares your opinion and 
my own as to the intention shown by the moth. We notice that almost 
invariably the moth goes down to near the base of the stamens, then 
creeps up, gets settled between two stamens and backs down a consid- 
erable distance while testing the surface of the ovary with the ovipositor 124 
MISSOURI BOTANICAL GARDEN. 
before puncturing it. This year for the first time I have seen Pronuba 
at the anthers, once with Miss Johnson and Mr. Henry Hitchcock, once 
with Miss Johnson, and a third time with my wife. None of our obser- 
vations on this point could be made under a lens, the moth being more shy 
than at the other work. In the first case a moth that had been seen to 
oviposit and pollinate once stopped and made a deliberate tour of the 
nearly empty anthers of the same flower, apparently scraping them out 
with its tentacles as Boll describes it, and with much the motion seen 
when she is thrusting pollen into the stigma. Frightened from the first 
flower, she went to another on the same cluster and rather nervously 
and hastily explored two anthers, after which, owing to the movements 
of so many persons about the plant, she became thoroughly alarmed 
and after nervously running about in several flowers, flew away. In the 
second case a moth similarly scraped an anther (or coiled and un- 
coiled its tentacles in it) but was frightened by our motions and, the 
light being strong (7:15 p. m.), crept to the bottom of the flower, re- 
maining there in the usual diurnal resting position. In the third case 
my wife saw a moth go through the acts of oviposition and pollination 
twice, after which she collected pollen from four or five stamens of the 
same flower; on being called I saw the operation repeated on another 
stamen. The collection of pollen was not actually seen in either of these 
cases, but only the perfectly deliberate and intentional act of going to 
the ends of the filaments and gouging the anthers out with the tentacles, 
and the observation was not close enough in any case to say that the 
moth did not meantime bring the pellet together by a lateral motion of 
the maxillae and round it in the manner described by you. But the act 
could have had no other object than the collection of pollen; and the 
third moth, which was caught, had a fresh ball of pollen. 
"Above Manitou, where it is abundant, I studied Y. angustifolia in the 
first ten days of July, this year; - in fact was there for that purpose 
when your first letter came to St. Louis. Females (weathered) were 
invariably with pollen. One of them (No. 31) was seen to oviposit and 
pollinate twice, behaving precisely as in filamentosa. I was not fortunate 
enough to see the collection of the pollen on this plant. The difficulty I 
have had in watching this part of the work no doubt comes from the fact 
that the moth can in a few minutes accumulate pollen enough for many 
pollinations, so that it is a relatively rare operation. My observation on 
filamentosa (assuming her to have had pollen when thrusting the tenta- 
cles into the stigma in the first and third cases noted above) shows that 
she renews this load as it becomes exhausted. Males with very fresh 
wings were abundant in angustifolia flowers, and at the end of the bloom- 
ing period were much more quiescent than the females, for a male could 
be found head down after an interval of several hours at night when the 
flower was re-examined. One pair was seen in coitu in a flower. One 
was seen to be nervously exploring the base of a flower between the fila- 
ments, but certainly found little or no nectar, and I have not seen another 
possible attempt at feeding. In angustifolia the stigmatic secretion is 
more commonly abundant than in filamentosa, but there is no greater flow YUCCA MOTH AND YUCCA POLLINATION. 
125 
from the septal glands. Small beetles and flies were very abundant in 
the flowers and seem to feed on the pollen, collecting on the anthers for 
that purpose. The former may also gnaw the papillae of fllaments, for 
the stamens become sodden and wilt within a day or two when these 
beetles are present - but I have not seen the latter gnawing at them. 
In their operations upon the anthers these little insects sometimes dis - 
lodge a ball of pollen which falls down. In one flower with horizontal 
pistil such a lump was seen on the green style near its apex; but the 
probability of any pollen falling in this manner where it could develop 
its tubes in the stigmatic chamber, is very slight except in case of a pos- 
sible deformity of the pistil by the reflection of the upper stylar lobe - 
thus opening the chamber above - or the upbending of the style so that 
the opening was directed toward the uppermost stamen. Aphides and 
Coccinellids were of course very abundant, but play no part whatever in 
pollination. A fair number of capsules were set this year, and all I saw 
were found to contain larvae of Pronuba or to show the characteristic 
scars or constrictions where the moth had pierced the ovary. 
" Prodoxus was very abundant, and I send you a number of both sexes. 
Nos. 19, 32 and 33, [all of Prodoxus decipiens'] were seen ovipositing in 
stem of anjrusii/bZia, head upward, the abdomen being worked much as 
with Pronuba. Numerous Prodoxus were seen flying from flower to 
flower very actively, and the sexes were seen in coitu in a flower, the 
abdomens working much as in ovipositing. The female in the cases 
watched by me when ovipositing in the stem, crept up a short distance 
before laying each new egg. 
" Apropos of Meehan's idea that the Pronuba moth close-fertilizes the 
flower, I have seen females when undisturbed go from flower to flower 
here, and several times in the mountains a female was seen, without 
having been disturbed, to fly off horizontally from a plant on the steep 
mountain side, with every evidence of the necessity for a long flight be- 
fore finding another Yucca." 
We have in the structures and functions which are so 
characteristic of this Yucca Moth, admirable adaptations of 
means to an end, whether for pollinizing the plant or pro- 
viding for a future generation. The Pronuba larva rarely 
destroys more than a dozen of the seeds, so that several may 
develop within a single pod and yet leave many perfect 
seeds, while, for the reasons already stated, we occasionally 
have pods without a trace of the insect. 
There is between Pronuba and its food-plant a mutual 
interdependence which excites our wonder, and is fraught 
with interesting suggestions to those who are in the habit 
of reasoning from effect to cause. Whether we believe, as 126 
MISSOURI BOTANICAL GARDEN. 
I certainly do, that this perfect adaptation and adjustment 
have been brought about by slow degrees through the long 
course of ages, or whether we believe that they were always 
so from the beginning, they are equally suggestive. The 
peculiar structure of the flower which prevents self-fertiliza- 
tion, though on a superficial view it strikes one as a disad- 
vantage, is, in reality, of benefit, as the value of cross- 
fertilization has been fully established; while the maxillary 
tentacles of the female moth are very plainly an advantage 
to her species in the " struggle for life ; " and it is quite 
easy to conceive, on Darwinian grounds, how both these 
characteristics have been produced in the course of time 
from archetypal forms which possessed neither, and in 
reality we get a good insight into the process in studying 
the characteristics of other species of the family Prodoxidae. 
These peculiarities are, moreover, mutually and reciprocally 
beneficial, so that the plant and the animal are each influenced 
and modified by the other, and the same laws which pro- 
duced the beneficial specialization of parts will maintain 
them by the elimination of all tendencies to depart from 
them. 
The pollen grains would not adhere by chance to the 
rolled-up tentacles,* and we have seen how full of purpose 
and deliberation Pronuba's actions are. It may be that all 
her actions are the result merely of " blind instinct," by 
which term proud man has been wont to designate the 
doings of inferior animals ; but no one can watch her opera- 
tions without feeling that there is in all of them as much 
of purpose as there is in those of the female Pelopseus 
who so assiduously collects, paralyzes and stores away in 
her mud-dabs the spiders which are to nourish her young ; 
or in the many other curious provisions which insects make 
for their progeny, which, in the majority of instances, they 
are destined never to behold. Nor can I see any good 
* I refer here to the fllamento«e Yuccas. Where they are more dis- 
tinctly glutinous, as in Y. whipplti, the statement is, perhaps, less true. YUCCA MOTH AND YUCCA POLLINATION. 
127 
reason for denying these lowly creatures a degree of con- 
sciousness of what they are about, or even of what will 
result from their labors. They have an object in view, 
and 'whether we attribute their performances to instinct or 
to reason depends altogether on the meaning we give to 
those words. Define instinct as "congenital habit" or 
" inherited association " or, as I prefer to characterize it, as 
the inevitable outcome of organization, and most of the 
doings of the lower animals may justly be called instinctive ; 
but the instinctive and reasoning faculties are both present, 
in most animals, in varying proportion, the last being called 
into play more especially by unusual and exceptional cir- 
cumstances, and the power which guides the female 
Pronuba in her actions, differs only in degree from that 
which directs a bird in the building of its nest, or which 
governs many of the actions of rational men. 
THE BOGUS YUCCA MOTH. 
The natural history of this species, Prodoxus decipiens, 
has been elsewhere recorded ;• but it will be well to show 
here wherein it differs from the true Yucca moth, notwith- 
standing the close general appearance of the perfect insects, 
which resemblance has necessitated the most careful obser- 
vations and has often neutralized those which were care- 
less. The moths (Pl. 39, Fig. 2, a, 5.), in both sexes, 
are on the average considerably smaller than Pronuba, 
and, if anything, more abundant in the earlier opened 
flowers of Yucca filamentosa. The trained observer, how- 
ever, will have no difficulty in distinguishing them, espe- 
cially the females, even without close examination of the 
structure ; for he soon comes to recognize the bull-dog like 
appearance of the head of the female Pronuba, as also the 
difference in the terminal joints of the abdomen, that of 
Prodoxus being thicker and darker. The males are dis- 
tinguished with more difficulty, and yet here the small size 
* Ann. Entomologist, III, p. 142; Proc. Am. Ass. Adv. Sc. XXIX, 1880. 128 
MISSOURI BOTANICAL GARDEN. 
of Prodoxus and the darker coloring of the under surface 
and tip of abdomen will permit the separation ordinarily, 
and render more careful examination necessary only in 
exceptional individuals of both species, i. e., the smaller 
specimens of Pronuba and larger specimens of Prodoxus. 
Closely examined, the female Prodoxus is found to have no 
maxillary tentacles, (there being a mere protuberance in- 
stead at the base of each palpus, PL 39, Fig. 2, c.), and in 
fact never makes any effort either to gather pollen or work 
in the stigma. Her ovipositor (PL 39, Fig. 3, b) while 
having a similar construction homologically, is yet a very 
different instrument from that of Pronuba. The male is 
at once distinguished by his longer and darker, differently 
shaped genitalia (PL 39, Fig. 3, f, g). This species does 
not breed in the fruit of the dehiscent Yuccas, but may 
not infrequently be found in that of some of the non- 
dehiscent forms, like aloifolia. The egg is thrust into the 
flower stalk, while this is yet sufficiently tender, and ovi- 
position takes place usually before any of the flowers of Y. 
filamentosa are open. The first specimens are found, as a 
consequence, sometime before the flowering of this species. 
They are most abundant, however, when this Yucca begins 
to flower, and then diminish in number, though a few may 
be found even after the last of the filamentosa blossoms have 
gone. Thus it is always found associated with Pronuba, but 
in appearance antedates this last and more nearly corres- 
ponds with the blooming of Y. angustifolia, the stems of 
which species it most affects, wherever the two are grown 
together. Prodoxus is, in fact, in large measure dependent 
upon Pronuba, since, as we have already seen, the flower 
stems, especially of Y. filamentosa, die rapidly when 
none of the flowers are fructified, and it is doubtful 
whether Prodoxus could permanently perpetuate itself, 
except as a dependent on the efforts and effects of Pro- 
nuba. This species of Prodoxus is common in the South on 
Y. aloifolia, Y. rupicola, Y. gloriosa, and Y. filamentosa, 
and in the west on Y. angusti folia, and I have rarely broken YUCCA MOTH AND YUCCA POLLINATION. 
129 
open a dry flower-stalk of any species without finding its 
larva, or examined a green stalk without the evidence of 
oviposition by the female. 
I have often watched the act of oviposition which, though 
simpler, involves much the same motions as in Pronuba. 
The female has more difficulty in making an incision, and 
thisus manifest by the many abortive and tentative attempts 
which she makes in her movements from one part of the 
stem to another. When she has once succeeded in insert- 
ing the ovipositor, and is fairly at work, she becomes as 
indifferent to examination and interruption as Pronuba, 
under like circumstances, and has often given me time to 
make the accompanying sketch (Pl. 39, Fig. 4) in the 
strong glare of the light. The incision always leaves a 
slight discoloration in the stem which becomes still more 
noticeable subsequently and forms a sort of cicatrice. 
(Pl. 38 Fig. 4, a a). The ovipositor-working much as one 
would work the tip of a hand-saw in making an incision - 
cuts a channel at a right angle from the surface and about 
2mm. deep. The oviduct is short - not long and thread- 
like as in Pronuba - and the egg (Pl. 39, Fig. 3, /i) is 
found at the base of this channel. The plant-tissues sur- 
rounding the egg seem to be disorganized by the irritation 
somewhat as in the case of Pronuba, and it requires nice 
manipulation to trace the egg which is extremely delicate 
and easily ruptured and in color and appearance closely 
resembles the surrounding tissues. It is compressed, 
elongate and without pedicel. It is, however, plastic and 
variable in form according to position. The apodal larva 
is hatched and begins to burrow about the ninth day after 
the egg is laid and in its curved position and general appear- 
ance, looks much more like some Hymenopterous or some 
Rhynchophorous than a Lepidopterous larva. It is pellucid 
white in color with black ocelli and brownish mandibles. 
It molts three times, so far as I have have been able to 
trace, acquires full growth in about a month and is then 
more often of a pale emerald-green color. It (Pl. 39, Fig. 
9 130 
MISSOURI BOTANICAL GARDEN. 
1, a) possesses no legs whatever, and eats but a small 
part of the stem (Pl.39, Fig, 1,/) preparing in the autumn, 
for hibernation, a cocoon of white silk which is covered 
on the outside with its castings and which remains pro- 
tected within the stem. Before making this cocoon, how- 
ever, it generally eats a passage-way to the outer covering 
of the stem and lines this with silk, leaving but a very thin 
cap (y). The chrysalis is formed in the spring, and when 
about to give forth the moth, pushes its way out through 
this cap. This happens almost always toward evening and 
the moth escapes just as the shades of night help to shield 
it during its more helpless hours, from detection. 
Various species of the genus Prodoxus are found asso- 
ciated with the different species of Vucca, breeding either in 
the flower stems, the main stalk, or sometimes in the fruit, 
and they will be considered more in detail, in the second part 
of this article. It suffices here to state that Prodoxus de- 
cipiens is the only species thus far found east of the Rocky 
Mountains ; that while it is quite constant in coloration east 
of the Mississippi, it is often more or less spotted with 
black in Colorado and South Texas, and that it shows the 
same tendency to retardation in development already no- 
ticed in Pronuba, some larvae remaining in the stems two, 
three or four years. 
Where the stems are allowed to remain on the plant this 
Prodoxus becomes exceedingly abundant, and the stems are, 
when one year old, often seen to be riddled with the per- 
forations which the chrysalis made in issuing, and this is 
especially true of K. angustifolia. 
Where the stems are cut, as they ordinarily are, in our 
gardens, soon after flowering, the larvae are apt to be de- 
stroyed, so that the species becomes scarce. 
To recapitulate, the figures on Plate 39, will sufficiently 
indicate the structural details of Prodoxus decipiens and 
give emphasis to the differences which I have already 
pointed out between it and Pronuba yuccasella, in the larva 
(Fig. 1 a) being apodal (lacking even the thoracic legs YUCCA MOTH AND YUCCA POLLINATION. 
131 
which belong to Pronuba); in the pupa (e) among other 
differences, lacking the series of dorsal spade-like projec- 
tions; in the form of the claspers in the male moth (Fig. 
3,/*, g); in the much stouter and differently shaped ovi- 
positor of the female (Fig. 3, 6, cZ); and especially in her 
lacking the maxillary tentacles. 
Who, studying these two species in all their characters 
and bearing, can fail to conclude that, notwithstanding the 
essential differences that distinguish them not only speci- 
fically but generically, they have had a common ancestral 
origin ? Pronuba, depending for existence on the pollination 
of the flower, is profoundly modified in the female sex in 
adaptation to the peculiar function of pollination. Pro- 
doxus, dwelling in the flesh of the fruit or in the flower- 
stem, and only indirectly depending upon the fructification 
of the plant, is not so modified, but has the ordinary char- 
acters of the family in both sexes. In the former, the larva 
quits the capsules and burrows in the ground; it has legs 
to aid it in its work, while the chrysalis is likewise beauti- 
fully modified to adapt it to prying through the ground and 
mounting to the surface. The latter, on the contrary - never 
quitting the stem - has no legs in the larva state, and in the 
chrysalis state is more particularly adapted, by the promi- 
nence of the capital projection, to piercing the slight covering 
of the stem left ungnawed by the larva. The former is very 
regular in its appearance as a moth at the time of the flow- 
ering of the Yuccas in their native range. The latter ap- 
pears earlier, as the food of its larva is earlier ready, and 
the female could not oviposit in the riper stem. 132 
MISSOURI BOTANICAL GARDEN. 
PART II. 
This part may be looked upon as supplementary to Part 
I., and is intended to bring together some descriptive 
details, as well as some other details upon which the gen- 
eralizations in Part I. are based. In connection with the 
new species that will be characterized, it will be convenient, 
and of some advantage to those interested in the subject, 
to bring together the previous descriptions. 
INTERNAL STRUCTURE OF PRONUB A YUCCASELL A WITH REF- 
ERENCE TO THE REPRODUCTIVE ORGANS. 
We have already considered the chief external charac- 
teristics of the female. If we examine the internal anat- 
omy, we find that the ovaries are large and pyriform, 
composed of four multilocular tubes gradually enlarging to 
the point of insertion in the oviducts and with the opposite 
extremity prolonged into a binding cord attached to the tho- 
rax. The oviducts are rather short. There are two large 
sebaceous glands and two smaller accessory glands, and a 
large copulatory pouch connected with the oviduct by a 
short tube or canal which opens close to the entrance of the 
ductus seminalis, this leading to the receptaculum seminis. 
This receptaculum is nearly as large as the bursa, pyri- 
form, flattened dorso-ventrally when empty, but more 
rounded when filled with semen. Its chief characteristic, 
however, is a pair of curious brown radiate bodies the rays 
or spicules springing from a central hub, which looks like 
the disk of a composite flower. These bodies are attached 
at opposite sides of the pyriform sac and are so large 
and conspicuous as to be readily seen through the walls 
of the abdomen when this is mounted in balsam. The 
hub is concave from the outside and convex from the in- 
terior, the disc presenting a granulated structure and the 
spicules radiating from its margin obliquely into the in- 
terior of the sac. Each spicule, when closely examined, is 
seen to have along its inner border, a hollow groove run- 133 
YUCCA MOTH AND YUCCA POLLINATION. 
ning from the base to the extreme tip (Plate 40, Fig. 2, 
d). There are some seventy or more of the longer 
spicules and other shorter ones; but they vary less in 
length than in other species. In the impregnated female 
there is found within this receptaculum and almost filling 
it, what appears to be an inner sac with a narrow neck 
entering and following the neck of the receptaculum. 
This is doubtless but a combined mass of spermatic par- 
ticles or fasciculi forming what has been called by Lepi- 
dopterists the large spermatophore. The albumen-like 
wall or envelope of this mass is somewhat thickened as it 
approaches the hubs of the receptaculum but then suddenly 
becomes thin and is somewhat insecurely fastened to the 
hubs so that when the spermatophore is detached, there is 
practically an opening in each side at the point where it 
was attached to the receptaculum. There are three mem- 
branes to this receptaculum, an external or muscular, a 
middle or serous, and an internal or mucous. The strong 
fibers of the muscular coat radiate from the border of 
the hub of one of the chitinous bodies, and are inserted 
in a similar position upon that of the opposite side. 
They thus include the whole of the sac until toward the 
neck, where they change to circular constricting fibers, 
and thus continue through the duct. Plate 40, Fig. 1, a 
gives an enlarged view of this receptaculum, with a longi- 
tudinal section through the hubs at d, showing the large 
spermatophore or inner sac c, and the space between it and 
the walls of the receptaculum, showing the manner in 
which the hub and the radiate spicules are placed at d. 
In Pronuba yuccasella this receptaculum averages about 
1.7 mm. in length, by 1. mm. in diameter, the crusher or 
radiate body measuring 1. mm., the rays averaging 0.43 
mm. in length and the hub or axis 0.14 mm. in diameter. 
By way of exhibiting how very much more strongly de- 
veloped this receptaculum and its crushers are in yuccasella 
than those in any of the other species, I have introduced 
(Plate 40, Fig. 2) drawings of the similar organs of 134 
MISSOURI BOTANICAL GARDEN. 
Pronuba synthetica (a) ; P. maculata (5) ; and Prodoxus 
decipiens (c), drawn to the same scale. In P. synthetica 
the receptaculum averages about 1. mm. in length and 0.66 
in width ; the crusher has a diameter of 0.43 mm., the longer 
rays about 0.17 mm. in length and the axis or hub about 
0.10 mm. in diameter. The crusher in this species looks 
much more like a burr, there being 16 of the longer, 24 
of a shorter size, 32 yet shorter and a number of the 
shortest which graduate into the tubercular inner surface of 
the hub. In P. maculata the receptaculum has a length of 
0.66 mm., and a diameter of 0.5 mm. ; the crusher has a 
diameter of 0.4 mm., the longest rays a length of about 0.17 
mm., and the axis a diameter of 0.06 mm. In Prodoxus 
decipiens the receptaculum has a length of 0.65 mm. and a 
diameter of 0.3 mm. The crusher measures 0.09 mm. with 
the longest rays 0.05 in length and axis 0.02 in diameter. 
The axis is relatively longer than in the other species, and 
the spicules are much reduced in number. 
The object of these chitinous bodies has been somewhat 
of a puzzle, all the more difficult to solve that they seem 
to be quite exceptional, and, in the remarkable develop- 
ment which they here present, absolutely unique, so far as 
I have been able to ascertain. They attracted my attention 
in my earlier studies of Pronuba and I was glad to find, on 
visiting Dr. H. A. Hagen in 1880, that he had been very 
much interested, in his studies of Prodoxus, in the similar 
but smaller organs of that insect. His explanation of their 
function, as elaborated in the Zoologischer Anzeiger (Jan. 
1882), is doubtless correct, viz., that they serve to liberate 
the spermatozoa from the spermatophores, but he was in 
error in locating them in the bursa instead of the recep- 
taculum. The muscular arrangement which I have de- 
scribed is well suited to such a purpose. In the somewhat 
flattened receptaculum the spicular arms actually inter- 
mingle and the radiating muscular coat possesses the only 
arrangement of fibers which would enable a simple con- 
traction to bring at once the whole contents of the sac into YUCCA MOTH AND YUCCA POLLINATION. 
135 
the nest of pointed blades. At the same time an egress is 
afforded the liberated spermatozoa through the mouth of 
the duct - the only point not constricted by the radiating 
fibers - and once within its walls a successive contraction of 
its muscular fibers, like the vermicular action in the small 
intestines of mammals, would cause their ready descent to 
the oviduct. Thus the spicules not only serve to liberate 
the spermatozoa, but also to facilitate their egress through 
the attached base, where the spermatophore wall is thinnest. 
We have already seen, in the characterization of what 
may be called the external parts of the ovipositor, that it 
consists apparently of two principal joints, the basal part, 
when highly magnified, showing an imbricato-granulated 
surface, the granulations strongest basally, and diminishing 
distally, and each having a more or less distinctly marked, 
retrorse point, while the terminal part is smooth and ends 
in a delicate dorsal, chitinous saw and a strong serrate tip. 
It is the working of the ovipositor, however, by the 
rods connected with it to which I wish to draw more par- 
ticular attention here. On carefully dissecting the abdo- 
men, there are seen along the dorsal integument four large, 
distinct, tough, longitudinal muscular bands. Viewing 
them ventrally each is seen to be inserted upon the widened 
free end of a slender, brown, horny rod, strongly attached, 
by an accumulation of muscular tissue, to the base of the 
vagina. The two inner rods (Pl. 37, Fig. C, «, z) are 
nearly parallel, the outer two slightly divergent (&, &). 
When the ovipositor is withdrawn the two inner rods extend 
back beyond the others and reach to the base of the third 
abdominal joint or even somewhat beyond. These two 
inner rods converge to form the lateral walls of the ovi- 
positor proper, extending as dark streaks to its extreme 
tip. The ovipositor is therefore a continuous piece, and 
in reality not jointed, though appearing so from the dif- 
ferent sculpturing of the basal and terminal covering. 
THE OVIPOSITOR. 136 
MISSOURI BOTANICAL GARDEN. 
This basal and sculptured portion of the integument 
represents the part which is invaginated when the ovi- 
positor is withdrawn. The outer rods enter on either 
side of the walls of the anal joint, extending and at- 
tached to the tip of the vagina. This arrangement for 
the exsertion of the ovipositor is at once simple and admira- 
ble, the contraction of the muscles forcing out the inner 
rods and carrying with them the ovipositor, and also ex- 
truding the tip of the vagina. The flexible and extensile 
oviduct is contained within the hollow center of the horny 
sheath and is doubtless extruded by the contraction of the 
body walls. In the other two species of Pronuba here dealt 
with the rods-are rather stouter and relatively shorter than 
in yuccasella. 
This general internal structure of the female here de- 
scribed is common to all the three species of Pronuba so far 
known, but the receptaculum seminis and the radiate 
bodies contained in it are, as already stated, in none of 
them so large and conspicuous as in yuccasella. In P. syn- 
Ihetica they areabout half as large, with the spicules stouter 
and straighter and reminding one of some stiff-spined 
Echinid. In P. maculata they are yet smaller. The same 
general structures also obtain in Proxodus, with much modi- 
fication of the ovipositor, however, and the radiate bodies of 
the receptaculum are smaller and seem in some species even 
to be obsolete. In P. decipiens they are smaller in propor- 
tion to the size of the sac, which is itself much smaller and 
more elongate than in Pronuba yuccasella. The spicules, 
however, are relatively larger, though few in number. YUCCA MOTH AND YUCCA POLLINATION. 
137 
Generic Characters of Pronub a. 
THE SPECIES OF PRONUBA. 
Imago. - Primaries (Pl. 34, Fig. 3, A) elliptical, the apex subacuminate; 
disc closed, though somewhat indistinctly between marginal veins 5-8; 
12-veined, exclusive of sub-median (1, a) ; costal vein stout, connected 
with sub-costal near base, and not extending beyond middle of wing; 
the sub-costal vein sends, from about one-fourth its length from base, a 
branch which reaches costa where the latter commences to round off; it 
also sends, from about the middle of the wing, a branch through the discal 
space, forming an accessory discal cell, and sometimes considerably 
passing the disc, and forking outside, so as to form marginal veins 7 and 
8, though more often forking just at the transverse discal vein; a feeble, 
disco-longitudinal veinlet starts independently near the base, forks near 
the middle, and forms a second accessory discal cell; sub-median vein 
distinct only near the margin, and indicated by an opaque line along the 
basal half of the fold; internal vein feeble and bifid at basal third. 
Secondaries (Pl. 34, Fig. 3, i) broad, subacuminate at tip; shoulder 
slightly produced and armed in the with a long spine, and in both 
sexes with a tuft of long scales; 8-veined, exclusive of sub-median (1, 
a), which is distinct; disc entire; costal vein extending three-fourths 
of the length of wing; an independent, feeble, disco-longitudinal veinlet, 
forking about the middle of the wing, the upper branch sometimes con- 
siderably passing the disc, and then forking into marginal veins 5 and 
6, but more often forking at transverse vein; internal vein feeble and 
simple. Head (Pl. 34, Fig. 3, a, 9)> free, sparsely haired; epicranium 
flattened or depressed; ocelli obsolete; clypeus large; eyes round and 
salient; antennae filiform and simple in both sexes, nearly one-half as 
long as front wing, the basal joint long, bulbous, and twice as stout as 
the others; maxillary palpi (Fig. 3,6) very long, 5-jointed, the basal joint 
in the 9 produced into a long, stout, cylindrical, prehensile tentacle, armed 
with spines springing from flattened tubercles (c); this joint in the a 
mere blunt-pointed tubercle (dj, the other joints almost smooth; 2d, short, 
stout, and directed backward; 3rd, more slender, and as long again as 
2nd; 4th, thrice as long as 3rd; 5th, as long as 2nd, slender and subfu- 
siform; the tip generally notched; labial palpi (gj moderately covered 
with hair-like scales, reaching nearly to base of antennas; 3-jointed; basal 
joint curved and stout; 2nd, half as long and straight; 3rd, short and 
fusiform; tongue long and smooth. Legs with the front femora and tibiae 
short, the hind femora and tibiae long and stout; the usual single 
spur on the front, a pair on the middle, and two pairs on the hind tibiae. 
Abdomen 9 with the anal joint long, horny, nearly bare; the ovipositor 
long, extensile, formed of two rods, the membranous covering of which 
is imbricato-granulate at base, the tip horny, serrate, and with a serrulate 
dorsal wing; shorter, blunt, and slightly swollen at tip; the genital 
hooks large, sub-spatulate, symmetrical; the upper edge entire and 138 
MISSOURI BOTANICAL GARDEN. 
thickened, the lower edge excavated about the middle, with a tooth or 
tubercle in middle of excavation. 
Egg. - Soft, filiform and clavate. 
Larva. - With thoracic legs but without prolegs. 
Chrysalis.-With a capital projection and very strong dorsal ab- 
dominal spines. 
PRONUBA YUCCASELL A Kiley. 
[Pl. 34, Figs. 1, 2, 3,4.] 
Egg. - Thread-like, averaging 2 mm. in length, with a long pedicel 
and gradual enlargement toward apex which has a minute indurated tip. 
Larva (Pl. 34, Fig. 1, a). - Average length 14 mm. Broadest 
on thoracic joints, thence gradually decreasing to extremity, which is 
quite small. Color, carneous, with a paler greenish tint below. No 
piliferous spots, but a very few minute and short stiff hairs springing from 
the ordinary positions of such spots. A transverse dorsal wrinkle, on 
each of the principal joints, more or less distinctly divided in two by a 
medial-dorsal depression, which is sometimes slightly bluish. Joints 
deeply incised and with a lateral, sub-stigmatai, longitudinal wrinkle 
(Fig. 1, d). Thoracic legs stout but short, -with three joints and a claw. 
No prolegs. Stigmata (9 pair) forming a small rufous circle on anterior 
portion of joints 1 and 4-11. Head (Fig. 1, e, f, h, i, j, k) partially 
retractile, copal-colored; epistoma sharply defined; labrum slightly 
pilose; mandibles stout, rounded, and with four acute teeth, each 
diminishing in size from without; maxillse with the inner lobe rounded 
and furnished with (usually two) short fleshy hairs, the palpi four- 
jointed, the terminal joint with bristles; labium prominent, with the 
spinneret conspicuous and the palpi two-jointed - the first long, with a 
fleshy hair at tip, the second small, spherical, and also terminating in 
a fleshy hair; antennae two-jointed, the terminal joint with a bristle; 
ocelli pale, around a dark crescent. Cervical shield flattened and not 
well-defined., 
White when young; more or less green and rosaceous when mature. 
Mostly curved in the fruit, like the larvae of the Rhyncophora. 
Chrysalis 9? 34, Fig. 4, m, lateral view). - Average length 
8 mm.; greatest diameter about | the length. Thick and stout, with the 
dorsum greatly arched. Head with a prominent, conical projection on 
top and two smaller ones between the eyes. Most characteristic feature 
a series of six dorsal, arcuated, horny plates - one on the anterior half 
of each of joints 5-10. These plates have anteriorly 10-12 blunt, flat- 
tened, recurved projections, the largest in the middle from which the 
others are successively lessened. The ends of some of the larger ones 
are shaped like the share of the more common shovel-plow. In the first, 
row the arcuation is greatest, and the projections largest and directed 
most forward; all which features are gradually lessened with each suc- 
ceeding joint. Joint 11 has no plate, and but 4 posteriorly directed 
spines, while joint 12 has two broad and flattened dorsal processes. 
Tip of abdomen rounded and reaching beyond the processes. Each joint 
has a transverse series of stiff yellow hairs, and four such are quite 
conspicuous on mesothorax, and others on top of the head and on face. 
Color, wThen fresh, pale green, with the wing-sheaths darker. When 
mature, and just before giving forth the moth, the head, thorax, breast 
between the antenna;, and tip of abdomen, are light brown; the eyes, 
dorsal plates and projections, darker brown; the wing-sheaths and 
inter-spaces between dorsal plates, whitish; and the sides greenish. 
(Pl. 34, Fig. 4, I, dorsal view). - Distinguished generally by 
the somewhat smaller size; by the dorsal projections not diminishing YUCCA MOTH AND YUCCA POLLINATION. 
139 
on joints 8-11, but rather increasing in size; by the greater shortness 
of joint 11, and the greater length of joint 12; and by the apex not being 
so rounded, and not extending beyond the two broad anal processes. 
At maturity the maxillary pieces are somewhat flatter, owing, doubtless, 
to the fact that in 9 the spiny cylindrical tentacles lie stretched nearly 
their whole length, and cause them to bulge more. 
Imago (Pl. 34, Fig. 1, b, c). - Average expanse, 9 25 mm.; 
23 mm. Primaries, above, uniformly silvery white, the scales loosely set; 
fringes concolorous; beneath, pale fuscous, with a brassy reflection; 
paler internally; fringes either concolorous or paler; costa with a brush 
of dark hairs. Secondaries semi-transparent, pale fuscous both above 
and below; paler internally, the fringes white and the brush on shoulder 
dark. Head white; antennas and tongue dingy yellow; maxillary palpi 
of same color, with the exception of tentacle, which is darker; labial 
palpi with scales on second joint dark brown above; eyes black. Thorax 
white. Legs dingy yellow, more or less covered with pale scales. 
Abdomen with the terminal joint in 9 always bare, with the exception of 
a few short, stiff hairs near tip, and the scales on the other joints very 
loosely attached. 
Described from many specimens of both sexes. Remarkably uniform 
in characteristics, no other variation noticeable than in size. 
PRONUBA MACULATA Riley. 
[Pl. 42, Fig. 2.] 
The species was described (Proc. Am. Ass'n. Adv. Sci., 
Vol. XXIX., August, 1880), from two females and five 
males, taken by Mr. H. K. Morrison at Caliente, Kern Co., 
California, upon the flowers of a species of Yucca, unde- 
termined at that time. Since then I have taken it in the 
flowers of Yucca whipplei near San Diego, Cal., and Mr. 
A. Koebele has reared it from larvae in the seed-pods of 
this same Yucca taken at Newhall, Los Angeles Co., Cali- 
fornia. 
In June, 1876, I received from the late Dr. C. C. Parry 
pods and flowers of this Yucca collected at San Bernardino, 
which showed evidence of Pronuba work. The pollen is 
abundant and quite glutinous, and the tentacles of the moth 
would seem to be fitted for dipping into and coiling around 
the same ; while the modification of the tongue plainly indi- 
cates that it is an accessory organ in this collecting and polli- 
nating, and adds strength to the suggestions already made 
(p. 110) that the tongue in this genus is not a sucking organ. 
The stamens in this Yucca are long and straight, the style 
short and constricted, and the stigma expanded and peltate. 
Of all the Yuccas it would seem to be most easily self-fer- 140 
MISSOURI BOTANICAL GARDEN. 
tilizable. Yet a Pronuba is needed and it will prove most 
interesting to observe her manner of working. 
Neither pollination nor oviposition has been observed in 
this species, nor is the chrysalis so far known, and I shall 
be very glad to get further facts upon the subject from 
those having opportunity to observe them. 
The habits of the larva are very similar to those of 
yuccasella. It leaves the pod as soon as mature, buries in 
the ground and spins a similar cocoon. I have known a 
few to remain in gathered pods, however, after having 
made the perforation which was partly closed with web, 
and though this would indicate that transformation may 
exceptionally take place within the pod, the fact has not yet 
been experimentally proved. 
Larva.- Average length 16 mm. Absolutely identical with that of 
yuccasella both in coloration and structure, the only difference notice- 
able being that, if anything, it is slightly more slender and with the 
thoracic segments less swollen. 
Imago (Pl. 42, Fig. 2).-Expanse, £, 19-21.5 mm.; 17-17.8 mm. 
Head white eyes black, mouth parts yellowish but very sparsely 
clothed with white scales; antennae yellowish, the tips fuscous, sparsely 
clothed with scales on the basal half only; maxillary tentacle (mt) 
yellowish, the base green, large, more swollen, much longer than the 
tongue, tapering toward tip which is often coiled spirally; hirsute rather 
than spinose, covered densely with fine hair, intermixed with scales, and 
a few spines on ventral side; maxillary palpi (mp) but half as long as 
tentacle with the basal or elbowed joint very prominent, the second joint 
not bulbous and the third joint relatively much shorter than in yuccasella; 
tongue (i) short, stout, swollen basally and, together with the maxillary 
palpi, hirsute (they are smooth in yuccasella) the hairs strong and 
spinous beneath. Thorax white; primaries (pr) with the upper surface 
opaque white, bordered with from 10-12 black spots (when all are 
present) of varying size and running from just beyond the middle of the 
wing to about the inner angle; the disc with 5 spots, 4 of them in a line 
from base to apex, the 2nd and 3rd rather farthest apart, the 
5th or middle one below and nearest the 3rd from the base; un- 
der surface deep fuscous, intensified around the borders and with 
the spots of upper surface barely indicated; fringes white; second- 
aries transparent, being very slightly covered with elongate fuscous 
scales, thickening on the borders, especially toward apex; fringes 
faintly fuscous; legs white, tarsi very sparsely clothed and yellowish 
except at extreme tips, which are more fuscous. Abdomen white be- 
neath, fuscous above. Integument of head yellowish; of thorax and 
coxae black or blackish. Terminal abdominal joint in £ short and 
thick, obliquely truncate from beneath (a) usually bare, honey-yellow 
with its base black; ovipositor stout, decurved, the terminal, horny joint 
(tjo) broad and rounded at the tip and at its edge finely denticulate. 
Claspers of J' short, abruptly curved upward, the base broad and 
rounded, the tip expanded, leaf-like, twisted, preceded by a deep excava- 
tion, but without tooth or tubercle (gs, side view; gp, posterior view) YUCCA MOTH AND YUCCA POLLINATION. 
141 
Described from 12 $>$>, 9 $$ from Southern California. 
In the specimens from Los Angeles Co., California, the 
spots along the anterior margin are, as a rule, considerably 
smaller, those at posterior border more or less confluent 
and often united with the terminal of the discal spots; 
while two or three of the remaining discal spots are want- 
ing. The apical fringe and a shade of the apex are 
distinctly dusky or blackish. The secondaries are some- 
what darker, especially toward the apex of the anterior 
margin, with a narrow blackish border all around and more 
or less distinctly dusky fringe. In specimens not rubbed, 
the anal joint of the female abdomen, and the male genitalia 
are freely covered with pale hair. 
Examination of the venation in one male shows that 
marginal veins 7 and 8 arise from the transverse vein inde- 
pendently of the discal branch of the subcostal vein and 
that the upper fork of the independent discal veinlet is 
wanting. 
In one of the male specimens only four of the spots on 
the border of the primaries are present, and in this speci- 
men, as well as in one other male and one female, the 
second discal spot is absent. 
PRONUB A SYNTHETICA, n. sp. 
[Pl. 41, Figs. 1, 2; Pl. 42, Fig. 1.] 
This is the most remarkable of the three known species 
of the genus and bears a striking general resemblance to cer- 
tain Saw-flies (genus Dolerus), both in color, habitus, and 
form. It also strongly recalls, especially in nature and 
with wings closed, certain Neuropterous species of the 
family Sialidse, as Sialis infumata. 
This general resemblance is due to certain characteristics 
which are quite abnormal in Lepidoptera, e. g., the naked 
and fuliginous wings, and the dark, polished and flattened 
body, with its broadened, horny and angulate tip. But it 
extends to other details. Thus the two metathoracic pale 
spots, exactly in the position of the cencri of the Tenthre- 142 
MISSOURI BOTANICAL GARDEN. 
dimdse, are more noticeable than in any other Lepidopteron, 
and while careful study shows them to be superficial and 
hardly homologous with the cencri they would seem to 
have some similar raison d'etre.* The broad and deep 
insertion between thorax and abdomen, with its contrasting 
coloring, also serves to increase the general likeness. 
Though I had briefly visited the tree Yuccas ( Y. brevi- 
folia) of the Mojave desert, in March, 1887, it was not 
until April 14th, of the same year, that I was able to spend 
a whole day among them, mostly in the Antelope Valley. 
There were but few specimens in bloom, but a number 
showed the old fruit, and it was with no little satisfaction 
that in almost every case I found that this indicated 
the presence of some Pronuba of a relatively large 
species, as evidenced by the holes of exit of the larva. 
The flower has the perianth very dense, the petals thick, 
fleshy, almost leathery, curved in at the tips, the bracts 
large and tough. Mr. Koebele was with me at the time, 
also Mr. Frank Godey and Mr. J. G. Wickersham. On 
account of the scarcity of the flowers, and the difficulty 
of reaching them without disturbing the moths, but 
two specimens of this Pronuba were obtained; but the 
small white Prodoxus sordidus was abundant in the 
flowers and its work everywhere noticeable in the 
flower-stems. From the fact that I could not be 
among those curious Yuccas at night, I was unable to 
witness the acts either of pollination or of ovipo-sition 
of its particular Pronuba. The structure and characteris- 
* The structure and function of these cencri spots in Hymenoptera 
seem to be little understood. They vary in structure in different families, 
but for the most part consist of a membrane or lid which covers a cav- 
ity and suggests that they are sound-producing organs. In Lepidoptera 
the similarly placed, but superficial spots, are not specialized, but mere 
inflations or modifications of the chitine wall. They are wanting in the 
Rhopaloceraand higher groups of Heterocera, while in the Tortricina and 
Tineina, in which they are usually well developed, they have remained 
unnoticed because usually hidden by the vestiture, or not conspicuous, 
through lack of contrasting coloring. YUCCA MOTH AND YUCCA POLLINATION. 
143 
tics of the species are, however, well adapted to the work 
it 'has to perform in the densely packed and but partially 
opened flowers of this Yucca with their denser petals and 
firmer pistils ; for all the parts which are representative of 
the other species of Pronuba are here more stout, and the 
denuded and flattened body is well suited to creeping 
between the flowers. There is no question but that the 
tree Yuccas represent an ancient type of our flora, and 
Pronuba synthetica may also be looked upon as an ancient 
type of our Lepidopterous fauna. That it should have so 
many striking peculiarities that recall insects of other 
orders, is, therefore, very suggestive. I was very anxious 
to obtain the larva and chrysalis of this species, and the 
following year Mr. Koebele, at my request, revisited the 
tree Yuccas and succeeded in May, 1888, in obtaining 
infested fruit. As soon as this was received, the 
larvae left the pods and entered the ground, some of them 
forming cocoons almost identical in appearance with that 
of yuccasella. Others remained in the larva state, without 
forming cocoons. Indeed, one peculiarity noticeable was the 
great length of the larval life, as a few had not yet formed 
their cocoons by the end of 1889, or more than a year 
from the time they were received, while one was living and 
unchanged, in its cocoon, in August, 1891, or nearly two 
years and a half from the time it left the fruit. However, 
most of those that were reared to the imago state, whether 
by Mr. Koebele in California or at Washington, issued the 
following March or April. These facts would indicate that 
while normally the moth is produced the ensuing year, yet 
belated individuals may not issue from the ground until the 
second or even the third year, and I have been informed 
that it is not an uncommon thing for Yucca brevifolia to 
produce no flowers over large districts during some years. 
The tendency to retardation in development is, under these 
circumstances, advantageous to the species. 144 
MISSOURI BOTANICAL GARDEN. 
Larva (Pl. 41, Fig. 2, a). - Length when full-grown, 14 mm. 
Somewhat more cylindrical than that of yuccasella, the general color 
being bluish-green tinted with a rosaceous hue; otherwise undiStin- 
guishable from those of the other two species. 
Chrysalis (Pl. 41, Fig. 2, b, c). - In size, general shape and arrange- 
ment of the spines similar to that of yuccasella, but readily distinguished 
by the wing-sheaths in both sexes reaching only to the sixth abdominal 
joint and the posterior legs to the seventh, whereas in yuccasella the 
former reach to the eighth and the latter to about the middle of the 
ninth. The medio-dorsal spines are also longer, more prong-like and less 
spatulate, while the capitate spine is perhaps less prominent. The dif- 
ference is more particularly noticeable in the greater length and promi- 
nence of the two spines on the second abdominal joint. The anal joint 
in the male is narrower and comparatively longer, and the two terminal 
teeth much shorter than in the female, also not so well defined as in 
yuccasella. The anal segment in the female is broader and stouter than 
in yuccasella, with the teeth shorter, stouter and further apart, (c, d, e, 
f,ff,h.) < 
Imago (Pl. 41, Fig. 1, a). - Expanse £, 15-20 mm.; 16-18 mm. 
Body flattened, piceous. Wings smoky-gray; the scales sparse and as 
easily lost on the upper surface, especially of primaries, as in the Sesiidae, 
so that none butthose carefully killed soon after issuing from the chrysalis 
show the wings well covered. In such specimens the general color is 
cinereous, the primaries but slightly darker than secondaries, the scales 
being narrow and elongate, mostly gray, but with an admixture of black 
ones. The exposed membrane of the wing is fuliginous except a nar- 
row discal space and more or less of the costal region which remain 
sordid white. Fringes paler but sparse and easily lost except at anal 
angle of hind wings, where they persist. Veins black and strong. Body 
but sparsely clothed in freshest specimens and soon becoming bare 
except at neck; highly polished and minutely punctate, and in some 
specimens with metallic tendency. Head 1, 6) with the hair pale 
ferruginous; eyes brown, naked; labial palpi bownish-black with sparse 
white scales; maxillary tentacles stout and brown, shorter than tongue; 
max. palpi nearly as long as tentacle, basal joint stout, rounded, joints 2 
and 3 short, sub-equal in length, joint 4 very long, terminal joint with 
two spines at tip; tongue very stout, long and ferruginous; antennae 
black. Thorax with two singular transverse-ovoid translucent and 
somewhat opalescent spots recalling the so-called cenchri of Tenth- 
redinids; legs stout and dark, the hind tibiae and tarsi pale ferruginous. 
Abdomen separated from thorax dorsally by a broad and deep suture 
which is pale rufous by contrast with the general piceous color; anal 
joint (Pl. 42, Fig. 1, c, d~) in 9 rufous, with darker shade at base, 
the sides compressed from above and expanded into a broad and ungu- 
late wing, the borders of which are thickened and stiffened and con- 
verge to a rather sharp tip which is, however, obliquely truncate from 
the side;.ovipositor issuing generally at right angles and with the same 
parts as in yuccasella but all stouter and shorter (e,/). In the the 
dorsal fulvous suture or pit between thorax and abdomen is more pro- 
found and concave, the abdomen is less flattened and the claspers are 
brown, very stout, one-half as long as the abdomen, the basal part 
broad and leaf-like, the terminal part abruptly curved upward, dilated 
into a decurved triangular tip, and the prong quite long, slightly curved 
and denticulate at tip (a, b). 
Described from 28 9 9, 10 JV, from the fruit of Yucca brevi- 
folia. YUCCA MOTH AND YUCCA POLLINATION. 
145 
THE SPECIES OF PRODOXUS. 
It is my design to give here descriptions of all the species 
so far as known. The early stages of these different species 
are remarkably similar and it is extremely difficult - at 
times quite impossible - to point out characters by which 
to separate them. It will be well, therefore, first of all to 
reproduce the original description of Prodoxus decipiens, 
somewhat amplified, and merely describe the others by 
comparison. The ovipositor varies in appearance according 
as it is extruded or not. 
Generic Characters of Prodoxus. 
Imago.-Agreeing with Pronuba, except in the following important 
particulars: The basal joint of the maxillary palpi in the female is not 
produced into a spinous tentacle, but is formed just as in the male, being 
a mere blunt-pointed tubercle. 
Larva. - Apodous. 
Chrysalis. - Without prominent dorsal spines. 
prodoxus decipiens Riley, 
Egg.-Soft, white, easily yielding to pressure, and hence variable in 
shape, but usually elongate, rounded at both ends about 0.4 mm. in 
length, and less than 0.1 mm. wide. 
Larva (Pl. 39, Fig. 1, a).-Length 5 to 7 mm. Apodous, plump, 
broadest on joints 2 and 3, tapering thence posteriorly, with the dorsum 
strongly arched and the head and prothoracic joint more or less fully 
bent down on the breast. The body is glabrous and not conspicuously 
wrinkled and the general aspect strongly recalls some Hymenopterous or 
Rhyncophorous larvae. Head small, retractile. Stigmata placed as in 
Pronuba, i. e., the first pair on the hind portion of the prothorax and 
rather lower down than the succeeding 8 pairs, which are on the anterior 
portion of joints 4 to 11, the prothoracic spiracles somewhat largerthan 
the rest. Color of body either pale yellowish-white, or emerald-green, 
this last being the more usual color of the mature and especially of 
the hibernating specimens. The head is honey-yellow with a dusky spot 
on each side, a dash on each suture of the epistoma, the mouth dark 
brown, the mandibles black, labium and maxillae white; the mandibles 
have four teeth, much blunter than in Pronuba, though the labial palpi 
are smaller and more plump and the labium and maxiilae do not surpass 
the mandibles. The cervical shield is not defined as in Pronuba, but 
consists of 4 chitinous patches of the same color as the head. 
Chrysalis (Pl. 39, Fig. 1, e). - Average length about 6 mm. Of 
the same color as in Pronuba but much more slender, with the dorsum 
less arched and lacking the characteristic dorsal, arcuated plates with 
their peculiar recurved, flattened spines, there being in place of them the 
barest indication of a transverse row of minute points or teeth not re- 
10 
[Pl. 39, Figs. 1, 2, 3, 4.] 146 
MISSOURI BOTANICAL GARDEN. 
curved but pointing posteriorly, near the anterior border of joints 6-11; 
joint 5, which is so strongly armed in Pronuba, being here perfectly 
smooth. Joint 12 in both sexes is unarmed as in but not in the $ 
Pronuba, while the terminal subjoint is much swollen and curved upward, 
with two minute spines taking the place of the broader, compressed 
processes in Pronuba. The capitate point is much stouter and beak- 
like, flattened and somewhat excavated laterally, so that the upper edges 
form each a sharp carina. The sexes are only distinguishable by the 
somewhat less swoolen sub-joint in the 9 and her longer leg-sheaths, 
which reach a little beyond the tip of the body, whereas in the J1 they 
fall short of the tip. 
Imago ?, (Fig. 2). Average expanse 16 mm. In general appearancf 
closely resembling Pronuba yuccasella, but the upper surface is ordi- 
narily more silvery and less creamy in appearance, and the dark 
shades, as of the eyes and the dark hairs of the palpi, front legs and tarsi 
and at the base of the costa on primaries, are more pronounced and black- 
ish. The under surface is somewhat darker, and the tip of the abdomen 
not truncate but pointed, and slightly beveled off superiorly. The 
terminal joint is swollen and darker than in Pronuba. The ovipositor 
is stout, dark brown, laterally flattened, between three and four times as 
broad as in Pronuba, shorter, the sculpture of basal portion closer, finer 
and ribbed, the tip obliquely cut off below and having a series of minute 
teeth, the ventral one being more conspicuously produced, and a series 
of eight or nine more prominent teeth along dorsal edge, while two dis- 
tinct grooves run along the whole length and several smaller ones are 
noticeable near the tip. (Fig. 3, a, d.) 
(-J*, Somewhat smaller than 9, the genitalia being more elongate and 
prominent than in Pronuba, the claspers extending fully twice as far, 
less recurved, and having on the lower border 4 small black points or 
tubercles, equidistant from each other. (Fig. 3, f, g.) 
Described from numerous specimens of both sexes, 
either found in the flowers or reared from the stems of 
different species of Yucca throughout the eastern States. 
All the specimens obtained or reared east of the Missis- 
sippi have been immaculate, with the faintest tendency to a 
few minute spots; but western forms, especially those from 
Texas and Colorado, show a greater tendency to maculation, 
the number of spots ranging from 1 to 5 or more, usually 
arranged along the middle in the form of a broad W, a dot 
representing each angle and each outer tip. When the 
basal spot alone is absent the four remaining present the 
figure of a rhomboid. When it is absent and there is 
another spot posteriorly we have the W inverted. When a 
single spot is present there is no regularity in its position, 
and it may be differently placed on the two opposite wings 
of the same specimen. There may also be more spots on 
one wing than on the opposite one, while I have seen speci- 
mens with the thorax spotted with two metathoracic mesial YUCCA MOTH AND YUCCA POLLINATION. 
147 
spots, one above the other. When there are more than 
five spots, the additional spots are ranged around the pos- 
terior border. These spots are sometimes so small as to be 
confined to a single scale. 
prodoxus marginatus Riley. 
[Pl. 43, Fig. 2.] 
This species was described in 1880 (Proc. A. A. A. S. 
Vol. XXIX.) from specimens collected by Mr. H. K. Mor- 
rison in Kern Co., Calif. I have since been able, through 
Mr. Koebele's collecting in 1886, to rear it from the peti- 
oles and basal portions of the pods of Yucca whipplei 
obtained in Los Angeles Co., Calif., in the flowers of 
which it is also frequently met with from the end of April 
to the end of June. Its habits, so far as they have been 
observed, are quite similar to those of decipiens, the larvae 
remaining within the petioles nearly a year, transforming 
and issuing during the ensuing month of April. No especial 
observations have been made on the method of oviposition 
and the egg has not yet been obtained. 
Larva. - Average length 3-4 mm. General color pale bluish-green. 
Head honey-yellow, marked each side of the clypeus with some more or 
less distinct but irregular dusky patches. The cervical plate con- 
colorous with the body, but marked in front and behind with two faintly 
dusky patches, otherwise agreeing precisely with P. decipiens. 
Chrysalis. - Except in the smaller size and less prominent spines and 
sculpturing, agreeing exactly with that of decipiens. This is especially 
true of the male chrysalis. The frontal tubercle in the female, besides 
being smaller, lacks the sharp lateral carinae and has on the sides a shal- 
low longitudinal channel or depression. The dorsal tubercles on the 
eighth abdominal joint are also transversely ovoid instead of being per- 
fectly cylindrical at the base. 
Imago (Pl. 43, Fig. 2).-Expanse 8-10 mm. Color white, the clothing 
of body very sparse, especially on the abdomen, and showing more or 
less distinctly the integument which is dark brown often with an aeneous 
tinge. Antennae bare towards tip and yellowish. Primaries ( Fig. 2, pr) 
satiny-white with a terminal blackband of varying width; under surface 
fuscous, almost black on costal and posterior borders; fringes white. 
Secondaries white with a broad costal and apical fuscous shade; under 
surface concolorous; fringes white. Apical abdominal joint of $ black- 
ish, slender, very obliquely truncate above, the tip blunt-pointed (Fig. 2, 
a). Ovipositor short and stout; the horny terminal joint gradually 
narrowed to the pointed tip, the upper edge very finely and acutely 
serrulate (Fig. 2, tjo~). Claspers of (Fig. 2, c) not dentate, their 
form much concealed by scales, the large arms broad and of nearly 
uniform width; large upper basal piece obtusely angulated in the middle. 148 
MISSOURI BOTANICAL GARDEN. 
Described from 21 $ § and 22 collected and reared in 
Southern California. 
The males are as a rule smaller than the females with the 
marginal band often much narrower, sometimes reduced 
to a small dot or even entirely wanting. 
prodoxus intermedius Riley. 
[Pl. 43, Fig. 1.] 
This species was described in the same paper as the pre- 
ceding from two female specimens taken by Mr. J. Boll in 
Texas and one taken by myself July 18th, 1887, at Ute 
Pass, Colo. No others have been taken since, and the early 
states and the male remain unknown. This species is very 
interesting as showing how closely, except in lacking the 
characteristic maxillary tentacle, the species of Prodoxus 
may come to the typical Pronuba. The character of the 
ovipositor in this Prodoxus would indicate that the species 
breeds perhaps normally in the fruit, notwithstanding it can 
have nothing to do with pollination. It would thus be en- 
tirely dependent for its existence on the efforts of Pronuba. 
Imago (Pl. 43, Fig. 1), $.- Expanse 28.5 mm. Coloration as in 
Pronuba yuccasella. Basal joint of the maxillary palpi not provided with 
a tentacle, but having a slight tubercle at the tip. Apical joint of 
the abdomen (Fig. 1, a) shaped as in Pronuba yuccasella, but slightly 
deeper and possibly a little thicker. Ovipositor, shaped as in Pronuba 
yuccasella, but slightly stouter, more acuminate at tip and with the 
serrations of membrane finer and more numerous (ijo). The sculpture 
of basal joint shows like very fine punctations in angular rows (ty'o). 
Described from 2 $ § from Texas and 1 § from Ute Pass, 
Col., July 18, 1887. 
prodoxus cinereus Riley. 
[Pl. 43, Fig. 4.] 
Originally described in the same paper as the preceding 
from seven males collected in Kern Co., California, by Mr. 
Morrison. Since that time I have obtained numerous 
specimens either from the flowers of Yucca whipplei, in 
Los Angeles Co., California, collected by Mr. Koebele, or 
reared from the flower stems of the same species of Yucca. YUCCA MOTH AND YUCCA POLLINATION. 
149 
The species prefers the main stem of the plant for purposes 
of oviposition. Stems, received in May, 1887, gave forth 
the moth during the latter part of that month, but others 
issued from the same stems during the same month of May 
in the consecutive years of 1888, 1889 and 1890, thus 
indicating great variation in the development of the species 
and a remarkable tendency to retarded development. The 
eggs and the early states have not been observed, nor the 
earlier states preserved and described. 
Imago fj'.-Expanse 12 mm. Head, thorax, legs and apical ventral 
joints whitish. Primaries ashy; secondaries and under surface of all 
the wings brown with a cinereous reflection. Tip of maxillary palpi and 
apical third of antennae black; the integument of body black. Claspers 
(Fig. 4, a, d) dark testaceous, similar in form to those of decfpiens 
but without teeth; large upper basal piece broadly rounded or subtrun- 
cate; the smaller piece beneath it of similar shape. 
9 showing no differences whether as to size or coloration of scales, the 
head being somewhat darker, on the average. Anal joint of same form 
as in decipiens, the ovipositor being more slender than in any of the other 
species of the genus and coarsely toothed along the entire upper edge. 
Described from many specimens. 
prodoxus jenescens Riley. 
[Pl. 43, Fig. 3.] 
This species was also described in the same paper as the 
preceding from 3 females and 8 males collected by Mr. 
Morrison, in Kern county, California, but I have since 
reared it from the main stems of Yucca whipplei, also 
collected by Mr. Koebele, at Newhall, Los Angeles Co., 
California. The egg and mode of oviposition have not yet 
been observed, but Mr. Koebele reports that the larger 
larvae (doubtless those which produce females) work in the 
stem with the head upward, while the smaller larvae work 
downward, and that they go through their transformations 
in the month of May. I have serious doubts whether there 
is any sexual difference in the position of the larvae in the 
stem, as might be gathered from his observation. 
Larva. - Attaining a length of 9 mm. with a diameter of only about | 
the length, and distinguished from the other species by this greater 
slenderness and relatively greater length. The body tapers but little 
posteriorly and the general aspect is more that of a Cerambycid larva 150 
MISSOURI BOTANICAL GARDEN. 
than of a Rhyncophorous larva. General color pale greenish. Head 
honey-yellow, darkest in front with a broad brownish anterior border, 
more or less distinct, and a narrow blackish lateral line and dusky mark- 
ings each side of the clypeus, thus resembling that of P. marginatus. 
The cervical shield with two or three more or less confluent faintly dusky 
spots anteriorly and 2 rather well defined somewhat quadrate black spots 
posteriorly. 
Chrysalis. - Scarcely distinguishable from that of decipiens, except 
by the smaller size, smaller spines, and finer sculpturing. The frontal 
tubercle is relatively shorter and stouter. 
Imago.-Expanse, 9 11.2-14 mm. General color, 
bronzy, the primaries with a distinct purple reflection. Under surface 
of thorax, the coxae and the femora clothed with white scales. Head 
whitish, with scattered black hairs; labial palpi with black hairs; 4th 
and 5th joints of maxillary palpi and the antennae, except at the base, 
black. Integument black. Apical abdominal joint (Fig. 3, a) swollen 
as in P. decipiens and obliquely truncate from above, but the tip is also 
truncate from beneath and the lower border is slightly excavated. 
Ovipositor short and stout, very broad; the upper border of the horny 
terminal joint (Fig. 3, tjo) thin, arched and finely serrate, the tip 
obliquely truncate beneath and at the base of the truncation forming a 
small, thin tooth, the base beneath forming a blunt tooth, the border be- 
tween these teeth retuse. Claspers of (Fig. 3, c) with no teeth on the 
arms beneath; the arms more slender than in cinereus and narrowed more 
abruptly near the base; the broad basal part with a small tooth at the 
apex within. Large upper basal piece forming a stout process at the apex. 
Described from 20 females and 38 males taken from 
Southern California, many of them reared from the main 
stem of Yucca whipplei. 
I have five specimens of this species, all females, two of 
them reared from the seed-pods of Yucca whipplei in May, 
1886, by Mr. Koebele, the pods obtained at Santiago, Cal- 
ifornia, while three specimens were given me by President 
H. W. Harkness, and Mary K. Curran, of the California 
Academy of Science, in April, 1887, and obtained from 
the flowers of the same Yucca. The adolescent states 
are still unknown. 
PRODOXUS PULVERULENTUS, n. Sp. 
Imago $.- Expanse 9-10 mm. General color, white; head with the 
antennae white, the basal half fuscous; eyes brown; palpi pale yellow- 
ish,hairs white. Thorax, with the hair mixed with a few blackish scales; 
primaries white, more or less densely sprinkled with blackish scales at 
the posterior third and sparsely so on the remaining portion. These 
dark scales produce a powdery appearance of the wings, the amount 
varying in the specimens before me, there being in two of them but a faint 
trace of the darker scales; secondaries white, with a broad dusky 
anterior margin; under surfaces more densely flecked with blackish 
scales and hence somewhat darker. Abdomen fuscous above, with a few 
long whitish hairs on the terminal two joints; venter and legs white. 
Tip of the abdomen shaped as in P. marginatus. YUCCA MOTH AND YUCCA POLLINATION. 
151 
PRODOXUS Y-INVERSUS, n. Sp. 
[Pl. 43, Fig. 5.] 
Specimens of both sexes of this species were reared from 
parts of a pod of an unknown species of Yucca (but doubt- 
less Y. baccata) received from Mr. D. C. Chapman, of 
Washington, D. C., who had obtained them in May, 1883, 
from New Mexico, the moths issuing during May of the 
following year. The larvae infest the fleshy portions of 
the pod and produce hard, gall-like swellings. The cocoon, 
which, as with the other species, is constructed within the 
burrow, is pale brownish, and resembles an elongate, cylin- 
drical bag, rounded at the base and cylindrical at the apex. 
When ready to transform, the larva retires to the lower third 
of the bag and separates it from the upper two-thirds by a 
dense, tough, delicate whitish layer of silk, thus dividing 
the cocoon into two unequal chambers. No larvae were 
preserved, but those which were noticed in cutting open the 
swellings showed a remarkable resemblance to those of 
decipiens. The chrysalis also has not been studied. 
Imago.- £. Average expanse 14 mm. 10-12 mm. General color 
white. Head, thorax, legs and abdomen white beneath, the hairs 
between the antennae occasionally yellowish. Eyes black; palpi white; 
tip of labials yellowish; tongue pale yellowish. Primaries (Fig. 5, a) 
marked with black as follows - a costal streak along the basal half, 
widening posteriorly and more or less completely fused with a round spot 
near its end. An elliptical or roundish spot about the middle of the 
wing at the basal third; a more or less sharply defined inverted-Y-shaped 
band across the posterior third of the wing, with its exterior arm 
generally connected posteriorly with a black patch which extends 
along the posterior border but is more or less broken at the extreme 
border and also along its inner margin. This terminal dark patch 
usually broadens toward the apex and is sharply cut off on the costa at 
about the outer fourth of the wing. Secondaries pale yellowish, darkest 
at apex; fringes concolorous. Undersurfaces with the dark markings of 
the primaries less sharply defined. Abdomen, brownish above, the 
male claspers (Fig. 5, b, c), yellowish-brown, almost bare, quite slender, 
and gradually narrowing toward the tip, which is almost acute; each 
arm is provided with 5 or 6 very small, cylindrical, acute teeth at the 
posterior edge; basal lobes are almost circular and concave at the 
inner side; upper basal plate triangular. Anal segment of the female 
obliquely truncate from above, but slightly so beneath, the ovipositor 
stout, yellowish-brown, its terminal part slender, compressed laterally, 
the upper edge of the apex being finely and acutely serrate. (Fig. 5, d, e.) 
Described from four males and seven females, no two of 
which are exactly alike in the marginal details of the 
inverse Y-shaped band, nor in those of the terminal patch. 152 
MISSOURI BOTANICAL GARDEN. 
PRODOXUS RETICULATUS, n. sp. 
I have but three females of this species, taken by Mr. 
Koebele in March at Los Angeles, California, but without 
any notes of habit. 
[Pl. 43, Fig. 7.] 
Imago.- $. Expanse 10-11 mm. General color, white. Body with 
whitish hairs, those of the head inclining to yellowish, intermixed with 
a few darker hairs, especially around the antennas; the terminal joint 
of the palpi pale fuscous; vestiture of the legs superiorly dusky, with 
a slight cupreous reflection. Primaries with transverse blackish bands 
as follows: An oblique basal band much constricted at middle so that 
costal half is usually triangular; a narrow baud along the posterior 
border and the intervening space between these two bands occupied 
by a broad W-shaped band, the outer arms of the letter running parallel 
with the basal and terminal bands. Fringes white. Secondaries gray; 
fringes somewhat darker. Undersurfaces gray, with a brassy reflection, 
the darker markings of the primaries being but faintly indicated. 
Abdomen with the anal joint perpendicularly truncate, the flexible basal 
part of the ovipositor rather broad at base and pale, while the terminal 
part is stout, sharp and browmish in color. 
PRODOXUS COLOR ADENSIS, n. Sp. 
[Pl. 43, Fig. 6.] 
Of this species I have seen but a single male, taken in 
1884, by Mr. Morrison, in Colorado. In general appear- 
ance, as well as in the genital characters, it seems to be 
quite closely related to P. y-inversus. 
Imago.- 11 mm. General color white and somewhat 
glossy, the hair of the head being faintly yellowish between the 
antennae. Eyes black; antennae white at basal third, the rest 
fuscous; palpi and tongue pale yellow. A few hairs on the max- 
illary palpi and the extreme tip blackish. Primaries (Fig. 6, a) with 
a well defined band starting at right angles from costa to basal third 
and then obliquing suddenly though slightly toward base; a somewhat 
similar band across the middle of the w'ing obliquing first in the opposite 
direction, i. e. posteriorly, and then almost parallel with the first band; 
and a forked or somewhat Y-shaped band across the posterior third of 
wing; a terminal black border connects with this Y-mark at anal angle 
but not at apex, and there is more or less black at base of wing. Sec- 
ondaries whitish above; fringes white. Undersurfaces faintly dusky 
with a slight aeneous reflection and the markings of the primaries less 
defined than above, and the secondaries somewhat dusky toward the 
apex. Abdomen brownish with the scales also brownish, especially 
along the sides, but white beneath. Claspers pale brown, covered 
with long yellowish hairs and almost identical in form wfith those of 
y-inversus (Fig. 6, b, c). YUCCA MOTH AND YUCCA POLLINATION. 
153 
PRODOXUS SORDIDUS, n. Sp. 
I first found this species in the flowers of Yucca brevifolia 
on the occasion of the discovery of Pronuba synthetica, 
while other specimens were subsequently obtained by Mr. 
Koebele. In general appearance the species seems nearest 
related to P. cinereus, being, however, much paler, with 
the greater portion of the hind wings white. 
Imago. - Expanse 8-10 mm.; 911-13 mm. General color creamy- 
yellow, the females showing the most white. A more or less distinct 
dusky or blackish posterior margin to the secondaries, the dark color 
broadening toward the apex. The undersurfaces have a tendency to 
metallic reflection and the darker color of the hind border of the second- 
aries is repeated. Abdomen grayish-brown dorsally, with iridescent 
reflection. Anal segment of 9 reddish-brown, obliquely truncate from 
above, the tip rounded. Ovipositor yellowish-brown, slender and finely 
denticulate along the upper edge. Male claspers similar in shape to 
those of decipiens but more slender, the base comparatively broader and 
the apex more abruptly rounded; the basal side-piece narrower and 
pointed at tip; the posterior edge with from 3 to 5 small slender teeth. 
Described from 5 males and 5 females. 154 
MISSOURI BOTANICAL GARDEN. 
EXPLANATION OF PLATES ILLUSTRATING YUCCA MOTH 
AND YUCCA POLLINATION.* 
plate 34. 
Fig. 1.- Pronuba yuccasella: a, larva; b, $ moth with 
closed wings; c, do. with wings expanded-nat. size; tZ, 
side view of one of the middle joints of larva; e, head of 
larva, beneath ; f, do., above ; g, thoracic leg of same; A, 
maxilla; Z, mandible; j, spinneret and labial palpi; 
antenna - enlarged. 
Fig. 2.- Pronuba yuccasella: moth soon after issuing 
from chrysalis, showing position of wings when expanding 
and before fully dried. X3. 
Fig. 3.- Pronuba yuccasella,: generic characters - a, 
side view of head and neck of female denuded, showing 
how the collected load of pollen (1) is held by the tenta- 
cles (2); (3, 4, 5, tongue, antenna and maxillary palpi;) 
b, maxillary tentacle and palpus; c, an enlarged spine; d, 
maxillary palpus of $ ; e, scale from front wing; /, front 
leg; g, labial palpus; h, i, front and hind wings denuded; 
anal joint of female with ovipositor partly extruded 
showing silk-like oviduct- all enlarged. 
Fig. 4.- Pronuba yuccasella: I, male chrysalis; 
female do. 
Fig. 5.- Mature pods of Yucca angustifolia : a, artifi- 
cially pollinized and protected from Pronuba; b, normal 
pod, showing constrictions resulting from Pronuba puncture 
and exit holes of larva; c, one of the lobes cut open show- 
ing larva within. 
plate 35. 
Fig. 1.- Flower of Yucca aloifolia showing stouter 
pistil and shorter style as compared with filamentosa. 
* The author is under obligations to Prof. Edwin Willets, Assistant 
Secretary of Agriculture, for the use of the illustrations Pl. 36, Figs. 
1, 2; Pl. 37, Fig. 2; Pl. 38, Fig. 2, and Pl. 41, Figs. 1, 2. The others are 
either from his drawings and previously used, or made from his studies 
especially for this article, by Miss Lillie Sullivan. YUCCA MOTH AND YUCCA POLLINATION. 
155 
Fig. 2.- a, longitudinal section of pistil of 'Yucca fila- 
mentosa showing (5, b) punctures of Pronuba, and (c, c) 
the normal position of her eggs in the ovarian cell-Xll; 
d, section of a punctured carpel 7 days after oviposition 
showing the egg yet unhatched and the manner in which the 
ovules in the neighborhood of puncture have been arrested 
in development so as to cause the constriction -X2; e, sec- 
tion of an older carpel showing the larva above the original 
puncture-X2; f, a seed 13 days from oviposition showing 
young larva at funicular base-X8. 
plate 36. 
Fig. 1.- Transverse section of one of the carpels of pistil, 
after the flower has opened: a, ovule; b, funiculus; c, 
placenta; <Z, ovarian cell; e, fibro-vascular bundles; 
fibro-vascular tissue ; y, primary dissepiment. 
Fig. 2.- Transverse section of pistil about middle, one 
day after oviposition, showing (a, a) puncture of oviposi- 
tor, and (6, d) position of egg-X17. 
plate 37. 
Fig. 1.- A, tip of anal joint and vaginal projection of $> 
Pronuba yuccasella from side showing ovipositor with 
parts extended: b, basal part; c, its file-like surface; d, ter- 
minal part with its dorsal serrate wing (/), its dentate tip 
(e), its ventral membranous outlet (g) and the extended 
oviduct (h); B, the same parts further enlarged; C, ven- 
tral view of tip of abdomen showing the two pair of rods 
i, i and k, k with their muscular attachments, the parts of 
ovipositor similarly lettered as in A ; m, m, eggs taken 
from Yucca pistil; n, egg showing development of embryo ; 
o, mature egg from ovary of $; r, s, genital claspers of 
lateral and dorsal views - all enlarged, the pedicels of eggs 
not sufficiently slender. 
Fig. 2. -Flower of Yucca with near petals removed to 
show normal position of Pronuba in ovipositing. 156 
MISSOURI BOTANICAL GARDEN. 
plate 38. 
Fig. 1. - Pistils of Yucca filamentosa, showing (a) a 
deformed specimen and (Z>, c, d) varying lengths of the 
stamens. 
Fig. 2. - Pronuba yuccasella, female, in the act of 
gathering pollen from the anthers-X5. 
Fig. 3. - Chauliognathus pennsylvanicus: a, larva; b, 
its head and prothorax; c, d, f, g, h, its mouth parts ; e, its 
leg; i, beetle - all enlarged but a and i. 
Fig. 4. - Flower-stem of Yucca showing scars resulting 
from oviposition of female Prodoxus decipiens (a, a) and 
pupal exuvia of same protruding (6, 6, 6). 
plate 39. 
Fig. 1.-Prodoxus decipiens: a, larva; b, head from 
above; c, d, left jaw and antenna ; e, pupa; /*, infested stem 
cut to show the burrows, castings, cocoons (2), exit hole 
{g) and pupa shell (h) - all enlarged but /, the hairline 
between a and e showing natural length. 
Fig. 2.-Prodoxus decipiens: a, imago, wings closed ; 
b, female do. wings expanded - nat. size; c, maxillary 
palpus with its basal tubercle enlarged. 
Fig. 3. - Genital characters of Prodoxus decipiens'. 
a, tip of $ abdomen rendered somewhat transparent; b, 
basal part of ovipositor; c, its sculpture; d, terminal part 
of same; e, its tip more enlarged; /*, genitalia of 3 from 
side; g, do. from above ; h, egg- all enlarged. 
Fig. 4. - Prodoxus decipiens: Female in the act of 
ovipositing-X3. 
plate 40. 
Fig. 1. -a, receptaculum seminis of Pronuba yuccasella, 
showing radiate bodies or crushers and muscular struct- 
ure ; 6, same, longitudinal section through axle of hub, 
showing the main sac and the inner sac at c and the radiate 
bodies in the intervening space at d- X40. 157 
YUCCA MOTH AND YUCCA POLLINATION. 
Fig. 2. -a, outline of receptaculum seminis of Pronuba 
synthetica; b, do. of Pronuba maculata; c, do. of Prodoxus 
decipiens, all drawn to same scale as figure 1; cZ, enlarged 
spicule showing ventral groove and a transverse section of 
same. 
PLATE 41. 
Fig. 1. - Pronuba synthetica: a, $ with wings expanded, 
hair-line showing natural size; b, lateral view of the 
head and neck, more enlarged, showing a purely lateral 
view of the trophi, not in pairs to avoid confusion. The 
maxillary palpus (mp) with its tentacle (mt); tongue 
(0; labial palpus (Ip); base of antenna (at); eye (e) ; 
front trochanter (/Q. 
Fig. 2. - Pronuba synthetica: a, larva, from side; b, $ 
chrysalis, ventral view; c, do., lateral view - nat. size in 
hair-line; cl, lateral; e, dorsal view of anal joints of ; 
f, g, do. of $; h, dorsal view of 2nd and 3rd joints of 
abdomen - all more enlarged. 
plate 42. 
Fig. 1.- Pronuba synthetica: a, enlarged view genitalia 
of $ from side ; 6, do., from behind ; c, anal joint of female 
with ovipositor exserted, dorsal view ; d, do., lateral view; 
e, ovipositor, dorsal view, still more enlarged; f, do., from 
side. 
Fig. 2. - Pronuba maculata: a, tip of female abdomen; 
bjo, basal joint of ovipositor; (/o, terminal joint do.; 
ov, oviduct; mp, max. palpus; mt, maxillary tentacle; t, 
tongue; gs, claspers of male from side; gp, do. from be- 
hind; pr, front wings showing arrangement of spots in 
two of the more common forms - hair-line showing nat. 
size. 
PLATE 43. 
Fig. 1.-Prodoxus intermedius: a, anal abd. joint of 
female-X10; bjo, basal jt. ovipositor-X40; s, its 
sculpture ; tjo, terminal jt. do.; ov, oviduct. 158 
MISSOURI BOTANICAL GARDEN. 
Fig. 2. Prodoxus marginatus: a, anal abd. jt. of fe- 
male- X26; bjo, basal jt. ovipositor; tjo, terminal jt. 
do. ; ov, oviduct; c, claspers of male from above-X18 ; 
pr, front wing - hair-line showing nat. size. 
Fig. 3. - Prodoxus cenescens: a, anal abd. jt. of female 
with ovipositor retracted-X15; bjo, basal jt. ovipositor; 
tjo, terminal jt. do.-X28; ov, oviduct; c, clasper of 
male from above - X18. 
Fig. 4. - Prodoxus cinereus: male claspers (a) from 
above-X8; and (d) from side-X15. 
Fig. 5. - Prodoxus y-inversus: a, left front wing - 
hair-line underneath showing natural size; b, genitalia of 
male, dorsal view-X14; c, do., lateral view-X18; d, 
anal joint of female with ovipositor exserted, lateral view - 
X20 ; e, tip of ovipositor still further enlarged. 
Fig. 6. - Prodoxus coloradensis: a, left front wing - 
hair-line underneath showing natural size ; b, male genitalia, 
dorsal view-X15; c, do., lateral view-X18. 
Fig. 7.-Prodoxus reticulatus: female with wings ex- 
panded - hair-line showing natural size. Rept. Mo Bot. Gaud., 1892. 
Plate 34. 
ear 
e' 
'l 
A 
h 
.7 
Fig. 1. 
r/ 
J 
5 
Fig. 2. 
\e\ 
7> 
9 
I 
HL 
Fig. 3. 
Fig. 4. 
a, 
z> 
CHARACTERS OF PRONUBA YUCCASELLA Rept. Mo. Bot. Gard., 1892. 
Plate 35 
Fig. 1. 
%1i 
LX 
X2 
.x8 
I 
z 
e. 
Fig. 2. 
OV'IPOSITION OF PRONUB A Reft. Mo. Bot. Gard., 1892. 
Plate 36. 
$ 
a 
£ 
d 
I' 
-e, 
'"<2 
Fig. 1. 
a 
b 
-b 
x/7 
Fig. 2. 
OVI POSITION OF PRONUB A. Rept. Mo. Bot. Gard., 1892. 
Plate 37. 
A 
Tn? 
B 
I 
7 
\e 
c 
<? 
Z/z 
J 
& 
3 
S 
n- 
/l 
a 
A 
i 
fc 
i 
£ 
u 
c 
Fig. 1. 
Fig. 2. 
OVIPOSITION OF PRONUBA. Rapt. Mo. Bot. Gard , 1892. 
Plate 38. 
6 
$ 
a 
Fig. 1. 
c 
L * 
? 
i' 
J' 
& 
Fig. 2. 
a- 
h\ 
cJ 
cl 
6 
a 
9 
e" 
Fig. 3. 
Fig. 4. 
PRONUB A AND YUCCA POLLINATION. Rept. Mo. Bot Gard., 1892. 
Plate 39. 
7l' 
Cf 
a, 
L 
j e 
' c 
Fig. 1. 
c. 
cl 
Fig. 2. 
a 
e 
Fig. 3. 
Fig. 4. 
PRODOXUS DECIPIENS. Reft. Mo. Bot. Gard., 1892. 
Plate 40. 
(V 
XX 
d/ 
CX 
Fig. 1. 
lX40 
i 
CL 
d. 
c 
Fig. ?. 
RADIATE ORGAN'S OF Kept. Mo. Bot. Gard., 1892. 
Plate 41. 
(J 
|//z/ 
a 
|z? 
b 
I 
Fig. 1. 
k 
cc/ 
6 
c 
Fig. 2. 
PRONUBA SYNTHETICA. Rept. Mo. Bot. Gard., 1892. 
Plate 42. 
rz 
6 
V' 
c 
cl 
Fig. 1. 
jPZ 
t 
X /S' 
,X /S' ' 
'x /g 
ct- 
< 
3s 
mt 
01/ 
Vj° 
3? 
Fig. 2. 
PRONUBA SYNTHETICA AND P. MACULATA. Kept. Mo. Bot. Gard., 1892. 
Plate 43. 
a - 
pr 
Fig 1. 
Fig. 2. 
a 
c 
Fig. 3. 
jOU 
a 
Fig. 4. 
Fig. 5. 
e 
Ct. 
z> 
Cs 
Fig. 6. 
Fig. 7. 
SPECIES OF PRODOXUS.