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Flies
P. G. Koehler and F. M. Oi
Several kinds of non-biting flies can be found in and around farms,
residences, and food-handling establishments. These flies can be harmful to
health, causing annoyance and discomfort. All filth flies (Table 1 ) have an
egg, larva (maggot), pupa, and adult stage in their life cycle. The adult fly
has 2 wings (the hind pair is reduced to a knobbed balancing organ).
Filth flies are usually scavengers in nature and many are capable of
transmitting diseases to man. Filth flies can usually be grouped according to
their habits and appearance as: houseflies and their relatives; flesh flies,
blow flies and bottle flies, filter flies, soldier flies, and vinegar (fruit)
flies.
House Fly
The house fly, Musca domestica ( Figure 1 ) is one of the most common of
all insects. It is worldwide in distribution and is a pest in homes, barns,
poultry houses, food processing plants, dairies, and recreation areas. It has
a tremendous breeding potential and during the warmer months can produce a
generation in less than two weeks. In many areas of Florida the house fly
breeds continually throughout the year
.
CREDITS: J. F. Butler, University of Florida
Figure 1. House fly.
House fly eggs are laid in almost any type of warm organic material.
Animal or poultry manure is an excellent breeding medium. Fermenting
vegetation such as grass clippings and garbage can also provide a medium for
fly breeding. The whitish eggs, which are laid in clusters of 75-100, hatch
within 24 hours into tiny larvae or maggots. In 4 to 6 days the larvae migrate
to drier portions of the breeding medium and pupate. The pupa stage may vary
in length considerably, but in warm weather can be about three days. When the
adult emerges from the puparium, the wings are folded in tight pads.
The house fly crawls about rapidly while the wings unfold and the body
dries and hardens. Under normal conditions this may take as little as an hour.
Mating occurs immediately. A house fly may go through an entire life cycle;
egg, larva, pupa to winged adult in 6 to 10 days under Florida conditions. An
adult house fly may live an average of 30 days. During warm weather 2 or more
generations may be produced per month. Because of this rapid rate of
development and the large numbers of eggs produced by the female, large
populations build up.
House flies are strong fliers and can become widely distributed by flying,
wind currents, vehicles and animals. Generally, however, flies are abundant in
the immediate vicinity of their breeding site. Under certain conditions, they
may migrate 1 to 4 miles, but are usually limited to one-half to 2 miles.
House flies feed by using sponging type mouthparts. As the fly moves about
from one food source to another, it samples and eats its food by regurgitating
liquid and dropping it on the food to liquify it. Light colored spots called
fly specks are visible signs of this type of feeding. Darker fly specks
associated with house flies are fecal spots.
The house fly's feeding and breeding habits along with its persistence for
invading homes and feeding on human food enable the house fly to spread many
intestinal diseases such as dysentery and diarrhea.
Resistance is a complex problem associated with chemical control of
insects. Recognized some 50 years ago, it is not a new problem. Defined,
resistance is the ability of an insect population to withstand exposure to
insecticides, and this is acquired by breeding from insects that have survived
previous exposures to an insecticide that did not wipe out the whole
population. The surviving insects are resistant because either biochemical
mechanisms (enzymes) enable them to quickly break down the insecticide or
behavioristic adaptations enable them to somehow avoid the insecticide.
Stable Flies
The stable fly ( Figure 2 ) or dog fly is a blood-sucking fly which is of
considerable importance to people, pets, agricultural animals, and the tourist
industry in Florida. Stable flies primarily attack animals for a blood meal,
but in the absence of an animal host will also bite man.
CREDITS: J. F. Butler, University of Florida
Figure 2. Stable fly.
Adult stable flies can fly up to 70 miles from their breeding sites. The
stable fly adult is similar to the house fly in size and color. The stable
fly, however, has a long bayonet-like mouthpart for sucking blood. Unlike many
other species of flies, both male and female stable flies suck blood.
The stable fly breeds all year in Florida although peak populations occur
from August through September or October.
Stable fly bites are extremely painful to both man and animal. When
hungry, stable flies are quite persistent and will continue to pursue a blood
meal even after being swatted at several times. Although the bite is painful,
there is little irritation after the bite, and few people exhibit an allergic
reaction to stable fly bites.
The most practical and economical method for reducing stable fly
populations is the elimination or proper management of breeding sources. It is
important to remember that stable flies cannot develop in dry materials.
Stable flies breed in three principal types of material:
* Green vegetation (e.g. green chop, silage, crop residues, and cut
grass),
* Seaweed and Bay grass deposits and
* Animal manure.
Flesh Flies
Flesh flies ( Figure 3 ) are a scavenger fly species that usually feeds on
carrion or meat scraps in garbage. They are medium- to large-sized flies and
usually have 3 dark thoracic stripes and mottled abdomens. Many of the common
species have a red tip on the abdomen.
CREDITS: J. L. Castner, University of Florida
Figure 3. Flesh fly.
Flesh flies retain their eggs within the body of the female until they are
ready to hatch. The larvae are deposited directly onto the food the immature
will be eating. The life cycle for the common species can be completed in 8 to
21 days.
The preferred breeding media around residences are decayed flesh, spoiling
meat, and manure. Usually garbage can meat scraps and dog food left outside
are abundant sources of flesh fly breeding. Flesh flies can breed in dead
rodents and birds in attics or wall voids of houses.
Blow Flies and Bottle Flies
There are quite a few species of blow flies ( Figure 4 ) and bottle flies
( Figure 5 ) which are found in and around residences. The greenbottle,
bluebottle, and bronzebottle flies are particularly abundant in Florida. In
urban areas these flies may be more abundant than house flies.
CREDITS: J. F. Butler, University of Florida
Figure 4. Blow fly.
CREDITS: J. F. Butler, University of Florida
Figure 5. Green bottle fly.
The blow flies and bottle flies usually have a metallic blue or green
color or both on the thorax and abdomen. These flies are strong fliers and
range many miles from breeding places. They are abundant during the warm
summer months.
Blow flies and bottle flies can breed on dead rodents and birds in attics
or wall voids of houses. They usually breed in meat scraps, animal excrement,
and decaying animal matter around houses. The adult flies are quite active
inside and are strongly attracted to light. The mature larvae are often a
problem when they migrate from breeding areas to pupate.
Blow flies usually lay eggs on dead animals or decaying meat. Garbage cans
have been known to produce 30,000 blow flies in one week. The life cycle
usually lasts 9-21 days from egg to adult.
Filter Flies or Moth Flies
Filter/moth flies (Figure 6 ), (drain flies), belong to the family of
flies called moth flies. They are 1/16 to 1/18 in in length; light gray to tan
in color. Their life cycle is 7 to 20 days. Adult flies have the body and
wings covered with dense, long hairs. Moth/filter flies breed in decomposing
organic material, such as moist plant litter, garbage, sewage, around kitchen
or bathroom sinks and water traps in plumbing fixtures.
CREDITS: J. L. Castner, University of Florida
Figure 6. Moth fly.
Soldier Flies
The soldier fly ( Figure 7 ) is a widespread pest which occasionally
becomes a problem in homes. The adult is a large fly about 1 inch long with 2
large translucent areas on the abdomen. The fly behaves like a wasp and is
similar in appearance to a mud-dauber wasp. The larvae prefer to feed on human
or animal excrement although they have also been known to breed in honey bee
colonies killed in walls of houses.
CREDITS: J. F. Butler, University of Florida
Figure 7. Soldier fly.
Most frequently the larvae are found in bathrooms migrating from the
septic tank or sewer line. The presence of the maggot under such circumstances
indicates the septic tank or sewage line is not working properly.
Vinegar (Fruit) Fly
Fruit flies ( Figure 8 ) are nuisance pests and contaminators of food.
Fruit flies usually breed in fruit, dirty garbage containers, or slime in
drains, feeding on yeasts that grow on organic matter.
CREDITS: J. L. Castner, University of Florida
Figure 8. Vinegar fly.
Each adult lays about 500 eggs which hatch and the larvae mature to adults
in 9-12 days. These flies are readily attracted to fruit, vegetables, and soda
bottles and cans.
Eye Gnats
Eye gnats ( Figure 9 ) are small flies, shiny black about 1/6 inch in
length. The adults are strongly attracted to moisture around the eyes and nose
of people outdoors. In mid-summer large numbers of eye gnats persistently
hover around the face causing considerable annoyance. Often eye gnats enter
the homes through open doors or windows. They are strongly attracted to light
and observed mainly on windows in large numbers.
CREDITS: J. L. Castner, University of Florida
Figure 9. Eye gnat.
Eye gnats breed in soil containing considerable organic matter, decaying
vegetation, and animal excrement. The life cycle varies from 7-28 days
depending on the temperature and moisture.
Hump-Backed Flies
Hump-backed flies ( Figure 10 ) are about 1/8 inch long with a small head
and large thorax, causing the fly to have a hump-backed appearance.
CREDITS: J. L. Castner, University of Florida
Figure 10. Hump-backed fly.
Hump-backed flies breed in decaying vegetation, animal debris, garbage,
and in ant and termite nests.
Dump Flies
Dump flies ( Figure 11 ) are about 1/4 inch long, black in color with a
shiny thorax and abdomen.
CREDITS: J. A. Hogsette, USDA
Figure 11. Black dump fly.
Dump flies breed in garbage and fowl excrement. The larvae are predacious
on larvae of other flies.
Secondary Screwworm Flies
Secondary screwworm flies ( Figure 12 ) are about 1/4 inch long, green in
color, shiny abdomen and thorax with thorax marked lengthwise with three dark
stripes. Their life cycle is 9 to 39 days.
CREDITS: J. L. Castner, University of Florida
Figure 12. Secondary screwworm fly.
They breed in dead tissue surrounding wounds in animals, fresh cut meats,
and garbage.
Control of Filth Flies
Sanitation is still the best method of controlling filth flies in and
around the home and on the farm. Flies seek breeding places where garbage,
animal droppings, or vegetation residues accumulate. Locate and thoroughly
clean such places. Dry, spread or somehow dispose of dog, cat, or other animal
excrement. Do not let garbage accumulate in the open and make sure garbage
cans have sound bottoms and tight fitting lids.
Good fitting screens on windows and doors are essential in preventing
flies from entering homes and kitchens. In areas with high humidity screens
last longer when made of aluminum, plastic, or fiberglass.
Copyright Information
This document is copyrighted by the University of Florida, Institute of
Food and Agricultural Sciences (UF/IFAS) for the people of the State of
Florida. UF/IFAS retains all rights under all conventions, but permits free
reproduction by all agents and offices of the Cooperative Extension Service
and the people of the State of Florida. Permission is granted to others to use
these materials in part or in full for educational purposes, provided that
full credit is given to the UF/IFAS, citing the publication, its source, and
date of publication.
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