NOTES ON JOINT WORMS. 
PROF. C. V. RILEY. 
From the Rural New-Yorker of June 20, 1885, Vol. 44, page 418. 
Mr. Elliot Luse, of Barry, Ohio, under 
date of May 4th, sent me samples of wheat- 
sti aw for inspection. He wjd|ps as follows: 
“Last Fall, when thrasmng, there was a 
hard straw that would come through with the 
grain. It was from ha'llinch to three 
inches in length: when cletSfed- witff a 
mill, I would get abmijtoue bushel of this 
out of 20 bushels We btm 
little about it at the This I 
commenced wltfi cut 
and ground feed. taken sick, 
and I sent for the He said it was 
worms, and gave her a which soon cured 
her. In less than a week another was taken, 
and had the same symptoms as the first. I 
concluded it must be in the feed. Examining 
the straw, I find such as I send you. In one 
piece, not over two and-a half inches, I found 
as many as eight worms. What are they, and 
will they injure the grain this Summer? I 
find them only in the wheat straw.” 
The insects in these straws proved to be the 
common Joint Worm (Isosoma hordei. Harr.) 
(Fig. 215), which was quite abundant in parts 
namely, I. tritici (Riley), and I. grande (Riley), 
Figs. 216, 217. 218, are quite different. These 
Fig. 216.—Isosome tritici, the wingless Joint worm Fly—showing female (f): larva 
(a, b): and rudimentary wing (i); with full developed wiDgs (g, h) of exceptional Indi- 
viduals.—After Riley. 
Fig:. 215. 
Isosoma hordei, the true Joint-worm Fly.—a. fem- 
ale. with her antenna and abdomen enlarged <c, e) b 
male, with same parts enlarged After Riley. 
of the country last season, and was a great 
pest 30 years ago. As noticed by Mr. Luse, 
the insect remains in the straw through the 
Fall and Winter, and the most satisfactory 
way to destroy it is to burn the infested straw. 
The fact that the hardened and solidified bits 
of straw, infested by the Joint Worm, came 
through the thrasher with the wheat, in such 
quantities, is a most interesting experience, 
and shows the necessity of cleaning wheat that 
has been infested by this insect and of burn- 
ing the hardened and swollen bits of straw. 
As the Joint Worm has evidently been on 
the increase for the last few years, I would 
recommend to wheat growers to examine 
carefully their cut straw at harvest time, and 
if the infested portions are found numerous, 
as is easily ascertained by the slight gall-like 
swelling and hardening of the parts affected, 
it should be burned, as they can very well 
afford to sacrifice the straw to lessen the in- 
jury the ensuing year. After Mr. Luse’s ex- 
perience, one cannot be too careful in cleans- 
ing the grain and in separating and destroying 
the infested straw. 
While speaking of this Joint Worm, I regret 
that Prof. A. J. Cook should have given 
such prominence to a redescription of this old 
and well-known pest. In reading over his 
account on page 314 of the Rural, I could 
not but feel that he was dealing with Isosoma 
hordei (Harr ) and specimens which he has 
kindly sent, at my request, prove beyond a 
doubt that my surmise was correct. The col- 
oration in this species is sufficiently variable 
to have induced Dr. Fitch to separate from it 
what he considered three distinct species, viz.: 
I, tritici, secalis and favipes. The researches 
of Walsh, and the experience of myself and 
others since, have shown these so called spe- 
cies to be one and the same, and the names 
have become mere variety names Prof. 
Cook’s species accords in every way with the 
Tritici variety, and the work, as shown 
by him, is that peculiar to this species; 
for while, ordinarily, it causes more or less 
of swelling of the straw, the solidifying and 
hardening often take place with no more swell- 
ing than indicated in his figure, and the 
habits of the other species that infest wheat 
Iosoma grande, larger Joint-worm Fly, female — 
After Riley. 
Fig. 217. 
Fig. 218. 
Iosoma grande. - d. larva; e, antenna; f, mandible 
g, pupa.—After Riley. 
two are known only in the female sex, and as 
Prof. Cook’s figures are lacking in structural 
accuracy, I send the Rural herewith figures 
of the three species known to infest wheat. 
The larva of Isosoma hordei occurs in num. 
bers usually near the joint, and produces veri- 
table galls, the affected stalk solidifying and 
the external swelling varying in prominence. 
The other two species, which may prove to 
be dimorphic forms, live singly in the stalk 
without causing any hardening or swelling. 
The larvae and pupae of all three species are 
so much alike that they cannot well be distin- 
guished by the most skilled, and Prof. Cook’s 
description, agrees better with the parasitic 
Semiotellus larva than with tint of Isosoma.