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Order: Diptera
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Common Name--Flies and Mosquitoes
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Names
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The order Diptera is pronounced "DIP-ter-a." The
name Diptera is taken from the Greek words: "di,"
which means two, and "ptera," which means wings.
This name refers to the fact that flies have only two wings,
although there are some that are wingless. Diptera and
Coleoptera are the oldest names of orders still in use. These
names were first used by Aristotle more than 2300 years ago.
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There are common names for many kinds of flies, including
mosquitoes, midges, gnats, bots, keds, crane flies, horse
flies, flat-footed flies, and fruit flies. Some common names
refer to entire families of flies, and other names, such as
house fly, refer to a single species. In Diptera, the word
"fly" is always written separately from the rest of the common
name. Many insects in other orders also are called flies,
such as dragonflies and sawflies, but their common name is
always written as one word.
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Diversity
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There are about 120,000 named species of flies in the world.
Some researchers estimate that more than a million species have
yet to be described and named.
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More than 19,500 species in 121 families are found in the
United States and Canada. About 1,800 of these species, or
10% of the total, are crane flies in the family Tipulidae.
Other families with more than 1,000 species each include
Chironomidae (midges), Cecidomyiidae (gall midges), Tachinidae
(tachinids), Asilidae (robber flies), and Dolichopodidae
(long-legged flies).
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Habitats
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Adult flies are often found on flowers, sap, feces, garbage,
and animals, both dead and alive. Aquatic larvae can be found
in streams, ponds, water in holes of tree trunks, and any other
place where water accumulates. Larvae of filter flies (family
Psychodidae) live in drains of sinks and sewers. The larvae of
certain flies in the family Ephydridae breed in the Great Salt
Lake in Utah. Another species of Ephydridae, Helaeomyia
petrolei, has larvae that live in pools of crude oil.
Other fly larvae live in the soil, under bark, in decaying
materials, in fungi, and in plants. Some flies are known to
live in nests of ants and termites.
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Form and Function
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Adult flies range in length from 0.04 to 1.6 inches, although
rarely they may be more than two inches long. Most flies
have very large eyes, and some of these eyes have thousands of
lenses. Eyes of some horseflies (family Tabanidae) have
beautiful color patterns. Stalk-eyed flies have eyes at the
ends of long projections from the head.
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Most flies are black, gray, or brown, but others have brighter
colors of yellow, orange, blue, and green colors. Some flies,
especially flower flies (family Syrphidae), have colors and
forms that mimic bees and wasps. Flies are often covered
with spines, setae (hairs), and occasionally scales. The
setae are arranged in distinct patterns which can help in
distinguishing different flies from one another.
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Most flies have a pair of wings on their mesothorax. The wings
can be transparent, or they can have different patterns. The
veins in the wing often are used to identify the different
families of flies. Flies also have a pair of knob-like structures
called halteres on their metathoraxes. The halteres are actually
hind wings that serve to stabilize flight, or to help the fly
stay on an even course of flight.
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Most flies have sucking mouthparts that are modified in different
ways. Some flies, such as mosquitoes, have piercing mouth parts.
Other flies, such as the house fly, have sponging mouthparts.
Some flies do not have functional mouthparts and do not feed as
adults.
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Many flies, such as mosquitoes, have a long antenna. This
long antenna may be thread-like or be feathery. The antennae
in many flies are short and three-segmented with a long hair,
termed arista, arising from the third segment. This arista
may be a simple bare hair, or it may be feathery.
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Larvae of flies are grublike and do not have legs. Larvae of
some flies, such as mosquitoes, have large heads and chewing
mouthparts. Larvae of many flies do not have a distinct head
or chewing mouthparts, and these are called maggots.
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Pupae of mosquitoes are called "tumblers" because of their
tumbling motion from the surface of the water when disturbed.
Many flies have a pupa enclosed in a puparium. The puparium is
the dried skin of the maggot that surrounds the pupa, similar
to the way a cocoon surrounds a moth pupa.
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Life Cycle
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Flies have complete metamorphosis with egg, larva, pupa, and
adult. Eggs are usually deposited on or near the larval food.
In some flies, such as those in the family Tachinidae, the eggs
hatch inside the female and the young larvae are deposited by
the fly. In a few flies, including the African tsetse fly,
the female nurses the larvae with glands inside her reproductive
tract until the larvae mature. The mature larva comes out of
the female and quickly pupates.
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Some species of gall midges (family Cecidomyiidae) give birth
to young without ever mating, which is known as parthenogenesis.
The bizarre thing about these gall midges is that the larvae
develop inside a mother larva, eventually consuming and killing
her. These larvae become mothers to be consumed by their own
larvae. This process continues for several generations until
the larvae do not bear young and pupate to form adult flies.
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Mosquitoes eggs will not hatch unless they are in water. The
water may be in a lake, puddle, bucket or other container, a
knot hole in a tree trunk, or other such place. The female
of a species in the genus Amigeres will lay its eggs
on its hind leg, and then stick its leg into water for the eggs
fall off. In the cold Arctic regions, mosquitoes may be in
the egg stage for more than 11 months, hatching only after the
snow melts. The larval and pupal stages last only a couple of
weeks, and the adult emerges to lay eggs that will hatch in
another 11 months.
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Larvae go through 3-9 stages (instars) before entering the
pupal stage. At the end of the pupal stage the adult fly
emerges and mates. Males of mosquitoes and midges swarm in
large numbers to mate. The humming of thousands of male wings
makes a sound that attracts the females. Males of other flies
have courtship dances, waving their patterned or spotted wings
to gain the attention of the female. Males of some balloon
flies (family Empididae) present the female with a gift before
mating. This gift is usually a small prey insect that is
wrapped in silk, resembling a small balloon.
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Form and Feeding Habits
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Diptera has more diversity in feeding habits than any other
order of insects. Various species are predators, parasites,
plant feeders, and scavengers of animal droppings and dead
plants and animals. Adult flies feed on liquid food, but
larvae of various species can feed on liquid or solid food.
Some species live most of their lives on or inside vertebrate
animals as parasites, and other species visit the animals to
feed on secretions from the eyes or noses. Mosquitoes and many
other biting flies have females that feed on the blood of
vertebrates, and some biting midges feed on the blood of
insects.
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Many adults and larvae feed on plants, algae, and fungi.
Some adults feed on pollen or nectar, and many feed on tree
sap. Many species have larvae that bore in stems and roots of
plants. Species in the family Agromyzidae have larvae that
are leaf miners. Larvae of fruit flies (family Tephritidae)
are serious pests of fresh fruit and vegetables. Overripe or
decaying fruit can be infested by larvae of small fruit flies
(family Drosophilidae). However, these flies actually are feeding
on yeast in the decaying fruit rather than the fruit itself.
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Species in the family Cecidomyiidae are known as gall midges.
These midges form distinctive galls on different plants. A
gall with an eye-shaped pattern is found on maple leaves. A
single leaf of the hickory tree may have four or more different
shapes of galls, each a different species, on the same leaf.
Depending on the species, a gall might include a single or
several larvae. Other gall forming Diptera include some
species in the family Tephritidae.
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Some flies parasitize other insects and arthropods. Big-headed
flies (Pipunculidae) are parasites of Homoptera (leafhoppers
and planthoppers especially), and thick-headed flies (Conopidae)
are parasites of bees and wasps. Some species of flesh flies
(Sarcophagidae) parasitize spiders. All the species in Tachinidae,
the second largest family in North America, parasitize other
insects, especially caterpillars, sawflies, and beetles.
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Many Diptera are predators on insects and other invertebrates.
Larvae of marsh flies (family Sciomyzidae) feed on snails and
slugs. Adults of long-legged flies, (family Dolichopodidae),
robber flies (family Asilidae), and many dance flies (family
Empididae) are predaceous on other insects as adults.
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Adults of some flies are external parasites of birds and
mammals and feed on the blood of the host. Although these
flies live most of their lives on the bird or mammal, they do
not kill the host as do the parasites of insects. Bat flies,
which may have winged or wingless adults, are external
parasites of bats. Louse flies include external parasites of
birds, but one wingless species is a parasite of sheep.
Larvae of these flies develop within the reproductive tract of
the adult female, and they change quickly into pupae after
being deposited by the mother.
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Internal parasites include larvae of bot flies and warble flies
(family Oestridae), which attack mammals. Warble flies attack
cattle, and the mature larva causes a bump (or warble) on the
back of the animal. Bot flies are parasites of horses, rabbits,
squirrels, mice, and other animals. The human bot fly,
Dermatobia hominus , occurs in Central and South America
where it usually is a parasite of cattle and other animals.
Some blow flies (family Calliphoridae) and flesh flies (family
Sarcophagidae) also may feed on living tissue of animals.
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Natural Enemies
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Predators of Diptera include amphibians, reptiles, fishes, birds,
insects, spiders, and other arthropods. Flies that feed on
dead animals have competition from carrion beetles (family
Silphidae) for the same food. The beetles carry small mites
(class Arachnida) that prey on the eggs of flies that come to
the dead animal. Some rove beetles wave the tips of their
abdomens in a circular motion to attract the attention of flies.
A fly that comes too close to the beetle is grabbed by the
beetle's long mandibles.
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Flies are also attacked by viruses, fungi, bacteria, and other
microorganisms. Dead flies often can be found inside a house
on a window pane. A close examination of this dead fly will
show that it is surrounded by a round ring of spores from the
fungus that killed it.
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Certain carnivorous plants can also be enemies of flies (and
other insects). Pitcher plants, sundews, and Venus fly traps
are some examples of plants that obtain some of their nutrients
from trapped insects.
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Olympic Feats and Other Strange Facts
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It would take approximately 1,200,000 mosquito bites to totally
drain the blood from an adult human.
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Yellow fever is caused by a virus that is transmitted by the
mosquito Aedes aegypti. It was one of the worse diseases
in the United States before the 20th century. The first capital
of the United States was in Philadelphia, Pennsylvania. The
capital was moved to New York City and later to Washington, D.C.,
because of the large numbers of Aedes aegypti mosquitoes
and cases of yellow fever in Philadelphia.
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Some bot flies, such as the human bot fly, do not lay their
eggs on their animal host. Rather, the female bot fly lays the
egg on a biting fly, such as a mosquito, and this biting fly
carries the egg to its animal host. When the mosquito bites
the animal, the egg of the bot fly hatches, and the larva
burrows into the animal's skin.
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House flies beat their wings at a rate of 330 beats per second.
Mosquitoes beat their wings at a rate of 600 beats per second.
Some midges beat their wings at a rate of 1,040 beats per second.
By contrast, a hummingbird beats about 75 times a second, and
the fastest that humans can contract their muscles repeatedly
is about 10 times per second.
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The larvae and adults of Scatella thermarum live in hot
springs in Iceland. The adults live on mats of algae that
float on the surface of the hot springs, but the larvae actually
live in the water that reaches temperatures of 118 degrees
Fahrenheit (48° degrees Centigrade).
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The larvae of some fungus gnats (family Mycetophilidae) can
spin webs of silk with their mouthparts. One silk spinning
species, Arachnocampa luminosa, lives in a cave called
the "Glow Worm Cave" in Waitomo, New Zealand. The larvae of
this species are luminescent, making light similar to that of
firefly beetles. The larvae use their glow to attract midges
that live in the cave. The midges become trapped in the
sticky strands of silk and are eaten by the fungus gnat larvae.
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The larvae of some species of fungus gnats in the genus
Sciara sometimes travel together across the ground in a
close file. They travel so close together that they resemble a
large worm or snake many feet long.
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The dehydrated larvae of an African species of Chironomidae,
Polypedilum vanderplanki, can withstand exposure to
liquid helium (at a temperature of -270° Centigrade) for up to
five minutes with a 100% survival rate.
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Larvae of some Chironomidae can live in mud and water with low
levels of oxygen. They have red blood, similar to mammals,
which is better for carrying oxygen through their bodies.
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The chironomid midge, Charoborus edulis, has swarms of
millions of individuals near lakes in Africa. Natives in these
areas collect the midges and press the bodies together forming
a type of bread called Kunga cake that is eaten.
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Black fly larvae live under rocks and other objects in fast
flowing streams. The larva spins a safety line of silk and
attaches it to their home in the water. If they get washed
away by the water's current, they can climb up their silken
rope to get back to their home.
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The larva of a soldier fly, Potamida ephippium (family
Stratiomyidae), is a scavenger in the ant nests of Formica
fuliginosa. The larva lives up to four years in these nests,
which is a very long life time for a Diptera larva.
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The phorid fly, Conicera tibialis , can live for more
than a year and have several generations inside coffins.
These flies feed on the dead bodies and are called coffin
flies.
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In Greek mythology, there was a woman named Musca who was a
beautiful and talented singer. She was, unfortunately, the
rival of the goddess Diana for the love of a fellow named
Endymion. Diana did not want a rival, so she turned Musca
into a fly. The genus of the house fly, Musca, was
named after the woman who was turned into the fly.
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The Good and The Bad
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The presence of a single buzzing fly can be a nuisance to many
people, and swarms of flies can be a plague, especially if they
are biting flies. Many flies are serious pests of crops, farm
animals, and humans. Flies cause more illnesses to and deaths
of humans than any other group of insects. Fruit flies, such
as the medfly, are major pests of fruits and vegetables. The
Hessian fly, which feeds on wheat, and the seed corn maggot
cause great losses of grain crops.
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The "love-bug" in southern United States, which is a fly named
Plecia nearctica (family Bibionidae), is a pest of the
automobile. These flies live as larvae in decaying vegetation,
and adults emerge in large numbers to mate. The mating flies
damage the paint and clog the radiators of cars, causing them
to overheat. At the same time, the cars’ windshields become
so splattered with the flies that driving can become hazardous.
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Mosquitoes transmit pathogens that cause malaria, yellow fever,
dengue fever, encephalitis, and other diseases. In addition to
human diseases, dog heartworm is transmitted by mosquitoes.
Malaria, which is transmitted by species in the genus
Anopheles, is the worst of these diseases. The World
Health Organization estimates that more than 500 million people
are infected with malaria each year. Of these, more than 2
million people die each year, primarily children living in
Africa.
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Many disease pathogens are transmitted by flies in areas of
the world outside the United States. The tsetse fly of Africa
transmits a pathogen causing African sleeping sickness. Black
flies (family Simuliidae) and sand flies (family Psychodidae)
also are involved in the transmission of serious diseases of
humans.
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House flies are major transmitters of pathogens that cause
dysentery, typhoid fever, and other diseases. Researchers have
estimated an average house fly in a residential area carries
1,941,000 bacteria, mostly on their mouthparts and the pads of
their feet. A single fly on a person's food can leave more
bacteria than hundreds (if not thousands) of cockroaches.
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On the good side, many flies are quite beneficial. Parasitic
and predatory flies aid in the population control of many pest
insects. Many flies also play an important role in recycling
dead plant and animal matter. Flies are the second most
important group of flower pollinators after bees and wasps.
Much of our knowledge about genetics is based on research that
has been done with small fruit flies (family Drosophilidae).
Flies provide food for many animals, and midge larvae are a
major part of the diets of many fish.
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Taxonomy
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Selected Families of North American Diptera
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Tipulidae (crane flies)
Bibionidae (march flies)
Mycetophilidae (fungus gnats)
Cecidomyiidae (gall midges)
Psychodidae (moth flies and sand flies)
Culicidae (mosquitoes)
Simuliidae (black flies)
Ceratopogonidae (biting midges, punkies, no-see-ums)
Chironomidae (midges)
Tabanidae (horse and deer flies)
Stratiomyidae (soldier flies)
Mydidae (mydas flies)
Asilidae (robber flies)
Bombyliidae (bee flies)
Empididae (dance flies)
Dolichopodidae (long-legged flies)
Phoridae (humpbacked flies)
Syrphidae (flower flies)
Tephritidae (fruit flies)
Agromyzidae (leaf miner flies)
Sciomyzidae (marsh flies)
Drosophilidae (pomace flies, vinegar flies, small fruit flies)
Ephydridae (shore flies)
Chloropidae (grass flies)
Anthomyiidae (anthomyiid flies, root maggots)
Muscidae (muscid flies, house flies, face flies, stable flies, tsetse flies)
Calliphoridae (Blow flies)
Sarcophagidae (flesh flies)
Oestridae (warble and bot flies)
Tachinidae (tachinid flies)
Hippoboscidae (louse flies)
Streblidae (bat flies)
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A complete list of Diptera families and additional photographs
are available at the USDA Systematic Entomology Laboratory
Web site on Diptera Flies! Flies!
Flies!.
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Selected References
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Arnett, Ross H. Jr. American Insects, A Handbook of the
Insects of America North of Mexico. New York: Van
Nostrand Reinhold Co., 1985.
Borror, Donald J. and White, Richard E. A Field Guide to
the Insects of America North of Mexico. Boston: Houghton
Mifflin Co., 1970.
Borror, D.J., Triplehorn, C.A., and Johnson, N. F.. An
Introduction to the Study of Insects. Saunders College
Publishing, 1989.
Dethier, Vincent G. To Know a Fly. Oakland, California:
Holden-Day, Inc., 1962.
Oldroyd, Harold. Natural History of Flies. World
Naturalists Series. Norton Publishing, 1964.
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Links
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For an extensive list of Diptera Web sites, go to the Links Component of the module.
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Picture Credits
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Dr. Ross E. Hutchins (Deceased)
Mississippi Entomological Museum
A crane fly
Mosquito larvae getting air with siphons
Goldenrod gall fly
Maggot of house fly
Pupa of mosquito in water
Tachinid parasite emerging from puparium
A nectar feeding male mosquito
Gall of Cecidomyiidae on maple
Predaceous robber fly
The house fly, Musca domestica
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