Flies (Order Diptera)

Pest Management In and Around Structures May 30, 2013 Print Friendly and PDF
Management of Pest Insects

in and Around the Home


Flies (Order Diptera)

Adult flies are recognized by two functional front wings and by two small structures, called halteres (modified hind wings), that are club-shaped and probably function in a flight-balancing manner. This group of insects is good at, as their common name suggests, flying. Therefore the best interventions are aimed at finding and eliminating the larval (immature, non-flying stage) feeding sites. The larvae of most pest species leave the feeding site and ‘wander’ some distance from their food source (usually wet conditions) to pupate (usually dry conditions).

Proper sanitation is the key to pest fly management. Remove garbage and other refuse at least twice per week to avoid fly problems. Crane flies (Tipulidae): Crane flies have long legs, a long slender body, and vary in body length from 1/16 to 1 inch. Some crane flies may resemble large mosquitoes. Color will vary depending on species, but one common species is light brown or tan. The larvae are called leatherjackets and can damage lawns by feeding on the roots of grass. Habits: Crane flies generally rest with their legs spread widely. Adults feed on nectar or do not feed at all; many have vestigial mouthparts. Once they become adults, most crane flies simply mate and die, all within a few days. They do not bite humans. Interventions: No action recommended. Might Be Confused With: mosquitoes. Fruit flies (Drosophilidae): The most common species have red/orange eyes, but not all fruit flies have red/orange eyes. Fruit flies often hover around and just above food (most often decomposing vegetable matter) prior to landing. Flies are 1/8 inch. Habits: Feed mainly on decaying vegetable matter, compost, rotting fruit, etc. Often found around salad bars and restaurants where vegetable matter and juices collect. Also called vinegar flies, since vinegar (acetic acid) is a  decomposition product of some rotting vegetable matter. Interventions: Find larval fly feeding site(s) and clean or otherwise throw away rotting fruit or vegetable matter. Remove garbage, including the plastic liner, and other refuse at least twice per week. Might Be Confused With: humpbacked flies, fungus gnats, moth flies. Fungus gnats (several families represented; mostly Sciaridae): Small (1/16 inch) fly with smoky black wings.  Y-shaped wing venation is characteristic. Habits: Often found in overwatered plants indoors or in otherwise wet conditions. Interventions: Find larval fly feeding site(s) and clean or otherwise dry out. If desired, apply a soil drench with an appropriately labeled liquid insecticide. Might Be Confused With: mosquitoes, fruit flies, humpbacked flies, moth flies.

Black Soldier flies (larva) (Stratiomyidae): Strongly-segmented larva, 3/4 to 1
inch, with two 1/16 inch protrusions from one end. Adult flies rarely seen, but
are 3/4 inch and appear wasp-like and with two clear spots on upper abdomen.
Habits: In homes, larvae usually found in the bathroom. Presence in bathroom
may be indication of sanitary (sewer drain or septic tank) problems because larvae
feed in putrid, wet conditions. This insect also lays eggs and larvae develop in piles
of damp organic matter such as compost piles. Like many fly species, larvae are
known to wander well-away from their breeding site into areas where they pupate.
Interventions: Find the larval food source and address the problem by sanitation
or moisture management. Might Be Confused With: adults look like wasps.

House flies (Muscidae: Musca domestica): The most recognizable of all fly species.
Black, drab, 1/4 inch, fast-flying, often numerous around garbage cans and related
refuse areas. Habits: Breeds in garbage, trash, animal waste, and other organic refuse.
Like most flies, found most frequently breeding in overly liquid or wet conditions.
Often associated with unsanitary, unkept conditions, such as areas abundant in
animal waste or human garbage/landfills. The term maggot is most commonly used in
reference to this fly’s larval stages. Because flies are pushed by prevailing, local winds,
their source may be from some distance away. Interventions: Proper sanitation and
exclusion is an effective means of reducing fly numbers. Indoors deploy and maintain
sticky traps associated with attractive lights (commercial insect light traps) and/or the
chemical attractant Z-9-tricosene. Be sure that indoor light traps are situated so that
they cannot be seen by flies from the outside. There is no scientific evidence to support
claims that a hanging bag full of water serves as a deterrent to house flies. Remove
garbage and other refuse at least twice per week. Might Be Confused With: blow
flies.

Humpbacked flies (Phoridae): Also referred to as scuttle flies or coffin flies. Often
scuttle about on the surface around and on infested materials. Humpbacked flies are
about 1/8 inch. Habits: Often associated with dead and decaying animal or plant
matter (e.g., dead insects, rotting potatoes), bacterial buildup in drains (drain and
sewer scum) in bathrooms and kitchens, and in/around garbage cans. Interventions:
Find and clean fly breeding site(s) and/or clean out drains. Make certain that the water
trap in the drain line (especially common in less frequently used sinks) is filled – if
the water trap dries out, flies and other pests that live in the drain lines will be able to
enter the building. Remove garbage and other refuse at least twice per week. Might Be
Confused With: fruit flies, moth flies, fungus gnats.

Midges (Chironomidae): Visual appearance similar to mosquito. Males with long,
feathery antennae. Habits: Most often associated with eutrophic, polluted lakes or
other bodies of stagnant or polluted water. Does not bite. Moreover, adults are shortlived
and do not feed. Strong attraction to lights. Often emerges in large numbers and
is attracted to light-colored surfaces, such as the sides of nearby buildings with bright
lighting. Interventions: Keep lights off during mass emergences. If desired, apply a
spot treatment with an appropriately labeled residual spray to the side of buildings
where midges are most abundant. Control of larvae in nearby bodies of water must be
conducted by a licensed professional. Never apply a pesticide to or around any body of
water. Might Be Confused With: mosquitoes.

Blow flies (Calliphoridae: many species): Also referred to as bluebottles and
greenbottles. Large, robust, fast-flying flies, 1/4 to 3/8 inch, commonly shiny and with
metallic blue, green, copper, or gray coloration. Some species strongly bristled, some
with stripes on their pronotum (upper thorax), and some with large, reddish-brown
eyes. Resemble house flies in their flying behavior. Habits: Flies attracted to and breed
in recently dead and decaying animals and animal waste. When suddenly present
in large numbers, and when present indoors (typically at windows sills), is highly
suggestive of a dead animal indoors (e.g., attic, crawlspace, wall void, fireplace, etc.).
Interventions: Find dead animal and remove it. Maintain window and door screens
to prevent entry into the house. Remove garbage and other refuse at least twice per
week. Might Be Confused With: house flies (especially the maggots).

Mosquitoes (Culicidae): Delicate, long-legged, 1/8 to 1/4 inch flying insect. Distinct
buzz from flying mosquitoes is the sound of their wing beat. The Asian Tiger mosquito
(Aedes albopictus), one of 60-plus mosquito species in Georgia, has distinct black and
white legs, while other species are dull brown. Habits: Female mosquitoes bite because
they require blood to produce the protein needed for egg production. Males of most
species feed on nectar from flowers. Like other blood-feeding arthropods (ticks, fleas,
and bed bugs), mosquitoes are attracted to carbon dioxide, as it is indicative of a warmblooded
host. Some people are indeed more attractive to mosquitoes due to chemicals
on the skin that make them more attractive than other people. Mosquitoes require  standing water for larval development. The adults are common in shaded, windprotected
areas with abundant vegetation (low growing ground covers and tall grass).
Many human-biting species are most active at dusk and dawn. Interventions: The
larval stage (wriggler) is least mobile and most vulnerable stage to any management
strategy. Eliminate standing water, clean gutters and remove containers that can hold
rainwater. Follow recommendations in the section Proactive Pest Management. Apply
floating briquettes that contain Bti (Bacillus thuringiensis subsp. israelensis) to kill the
larvae in standing water. When outdoors use a repellent to discourage biting by female
mosquitoes (males do not bite). See EPA website on repellents at
cfpub.epa.gov/oppref/insect. For more information see University of Georgia
Extension circular #782, Stinging and Biting Pests, at caes.uga.edu/publications.
Might Be Confused With: midges, crane flies.

Drain flies (Psychodidae: Psychoda spp.): Also referred to as moth flies. Oblong
or oval, appears moth-like, and is about 3/16 inch, wings fuzzy. Larvae up to 3/8
inch. Habits: Commonly found in bathrooms (breeds in scum in drains, showers,
overflows, toilet bowls, etc.). Adults rest motionless on walls until disturbed, and
then fly well. Need wet conditions to breed. When toilets have gone un-flushed for
an extended period, moth flies may lay eggs in the toilet tank, and larvae can be found
there. When the toilet is finally flushed, larvae can make their way into the toilet bowl,
where they are discovered. Interventions: Clean the inside of the drain of all scum
and detritus using a mild cleanser and a bristled brush. Never pour insecticides into
drain. Pouring bleach into drains is not effective. Make certain that the water trap in
the drain line (especially common in less frequently used sinks) is filled – if the water
trap dries out, flies and other pests that live in the drain lines will be able to enter the
building. To help determine whether a particular drain is infested, place a clear cup,
inverted, over the drain. If flies emerge from the drain, they will be trapped by the cup,
and can be seen. Might Be Confused With: fungus gnats, humpbacked flies, fruit
flies, and small moths.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.