[This tape was transferred from a 16mm film original by Colorlab for the National Library of Medicine, January 2012, HF 6253]
[Music]
[Federal Security Agency, Public Health Service, Presents]
[A Communicable Disease Center Production: Community Fly Control Series: Biology of Domestic Flies]
[Narrator:] Controlling flies effectively depends upon adapting the control methods to fly habits.
These habits will vary with the changing conditions of weather, temperature, and season of the year.
Therefore, the control operator must have a knowledge of fly biology to apply his measures to the right place at the right time.
Typical of most of the higher insects, the lifecycle of the housefly starts with an egg, from which comes the maggot or larva.
The larva forms a pupa, similar to the chrysalis of a butterfly, and from the pupa emerges the adult fly.
The eggs are laid in batches on decaying organic matter, and a single housefly may lay well over 500 eggs in her lifetime.
Under normal summertime conditions, the eggs will hatch in 24 hours or less.
The larvae feed voraciously and pass through several growth stages or instars.
When full-grown, they stop feeding, move to a drier part of the medium, and become immobilized.
Their shape changes and the outer skin hardens, becoming reddish-brown or black.
This is the pupal case in which the immature insect changes into the adult fly.
To escape, the fly breaks the pupal case by inflating the ptilinum, a bladder-like organ on the front of the head.
When the fly first emerges, the wings are small and the ptilinum extends prominently forward.
But soon the ptilinum disappears and the wings expand to full-size. The fly is now completely developed and will not grow any larger.
The total period from egg to adult is eight to 20 days, and there may be 15 generations a year.
When we talk about domestic flies, we should include several relatives of the housefly.
First, there are the blowflies, generally larger than the housefly and usually shining metallic blue or green.
When blowfly larvae attain full growth, they leave the breeding medium
and may crawl for several yards before burrowing into the soil to pupate.
Another domestic fly is the flesh fly, typically with a checkerboard pattern on the upper side of the abdomen.
Similar in appearance to the housefly is the stable fly. The chief difference is in the mouth parts.
The housefly's mouth parts extend downward and end in a spongy pad called the labellum.
Unlike the housefly, the stable fly is a blood-feeder, and its mouth parts project straight forward like a bayonet.
Flies are capable of a considerable flight range. Blowflies ordinarily cover a wider range than houseflies,
but under certain conditions both types will cover a distance of 10 miles or more.
This means that breeding sites some distance away may be the source of flies in the community.
The term breeding sites includes almost any decaying organic material
offering the necessary food and moisture for larval development.
In the fringe area these will include stock farms,
vegetable processing plants,
and especially open garbage dumps on the edge of the community.
When a fly population builds up to this extent, overcrowding may drive them to the nearby town in search of new breeding sites.
A brief survey of the average community will reveal many sources of flies:
household garbage, industrial waste. Here maggots are concentrated in the runoff from a rendering plant.
Food waste from markets and restaurants, and exposed animal carcasses.
This contact of flies with filth and bacteria makes them a menace to public health.
Adult flies are unable to eat solid food, they feed only on the liquid part of the rotting matter.
Then when they come into our homes to enjoy a bit of sugar, they first dissolve it
by regurgitating some of the same contaminated fluid into the sugar bowl.
But perhaps even more important are the familiar fly specks, or germ-laden excreta.
Certainly, there can be no doubt of the ability of flies to transport filth and disease organisms.
Removal of the breeding sources is the most effective measure of all in cutting down the fly population.
That is basic sanitation, a primary objective in community fly control.
But the use of insecticides is an important supplementary measure,
and here a knowledge of adult fly habits is absolutely necessary.
Flies will not always be found where we expect them.
For instance, they usually remain close to sources of food,
but at the approach of a storm, houseflies will leave these attractants
and gather at door or window screens in their attempt to find shelter indoors.
During the cool morning hours flies will rest on walls and fences in the sun.
But in the heat of a summer day the same flies will gather at cool moist places, such as this damp spot in a dirt road.
Consideration of these changing daytime habits of flies is the key to effective space-spraying.
At night flies are inactive, blowflies resting outdoors on wires, low branches, or more commonly on foliage.
Houseflies, on the other end, normally rest indoors at night.
By daylight, the control operator can recognize the preferred night resting places
by the concentrations of fly specks along cracks in walls,
on overhead electric wires or on ceilings and rafters, usually preferring the edges of boards and beams.
Control experts make use of this knowledge by examining walls and ceilings for indications of preferred night resting places.
These areas are then sprayed with residual insecticides, for here the flies will remain all night in contact with the poison.
However, residual insecticides are also effective where flies regularly gather in the daytime.
The recent widespread use of chemicals for fly control has brought to light another very important phase of fly biology.
Early in a fly-control program, applications of the insecticide give encouraging results.
But then the flies begin to increase in numbers and further use of the insecticide has little effect.
In short, the flies have become resistant to the spray material.
All of these facts make it apparent that fly habits do not conform to a fixed pattern.
That is why the control program cannot be reduced to a formula.
The successful operator must know fly biology.
He must know that the entire lifecycle of the fly, egg to larva to pupa to adult, takes place in or near the source of larval food.
He should suspect any accumulation material as being a possible source of flies, a source that should be eliminated completely.
Daytime conditions of weather and temperature will dictate where and when to space-spray,
while the location of fly specks will indicate nighttime resting places,
areas where the application of residual insecticides will give maximum results.
Consideration of these phases of fly biology means more efficient, more complete control of domestic flies.
[Music]