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Local animals in this group:

true flies, including mosquitos


What do they look like?

There are many different shapes of True Flies. They are soft-bodied insects, most are fairly small (less than 1.5 cm long) but a few can be larger (up to 4 cm!). Adult flies have only 1 pair of wings, unlike other insects. The second pair has evolved into small balancing organs that look like little clubs. Adult flies feed on liquids and have either thin sucking mouthparts (like Mosquitos) or sponging mouthparts, a tube with wider sponge at the end (like Flower Flies and House Flies). Most adult flies have large eyes, to help them see when they are flying. Many adult flies look like wasps or bees. Sometimes they look a lot like The larvae of True Flies all look like thick segmented worms, but they have many different shapes. They don't have jointed legs, unlike beetle larvae. Some have mouthparts and a distinct head, but most don't. The pupal stage of a True Fly is covered with tough skin. It may have some of its legs and body parts visible, or it may be hidden inside a larval skin, and just look like a brown capsule.

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • male more colorful
  • sexes shaped differently

Where do they live?

Flies are one of the most diverse groups of insects. There are over 150,000 species known from around the world, and there are certainly many still undiscovered. In the Great Lakes region there are probably over 2,000 species

What kind of habitat do they need?

True Flies can be found almost anywhere. Adults of many species are strong fliers, which helps them locate supplies of food for their larvae. Fly larvae are most common in damp habitats, and flies populations are largest in humid places with lots of moisture.

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

How do they grow?

True Flies have complete metamorphosis. Adult female flies lay eggs, and then small larvae hatch from the eggs. The larvae are often worm-like, and do not have jointed legs. They molt (shed their whole skin) several times as they grow. Then they transform into a pupa, which is a resting stage that transforms into an adult.

How do they reproduce?

Most female flies produce hundreds of eggs. They lay them on the food supply for their larvae. They are often very sensitive to the smell of the food, and can locate it from kilometers away.

  • Breeding season
    Flies breed when the weather is warm enough, and there is food for their larvae.

True Flies usually don't have much parental care. The female puts her eggs in the right place, and that's it.

  • Parental Investment
  • no parental involvement

How long do they live?

Most flies live less then a year. Many fly species survive the winter only as eggs. Others survive as pupae, and a few survive as larvae or adults. Unless they hibernate, adult flies don't usually live very long, often only a month or two, and sometimes just few days or weeks. Flies usually spend most of their lives as a larva or a pupa. Flies are eaten by many predators, so very few of them live as long as they can.

How do they behave?

Adult flies are usually active during the day when it is warmer and they can see as they fly. Fly larvae often feed continuously, day and night.

How do they communicate with each other?

Flies use vision more than most insects do. They also sometimes detect the vibrations of wingbeats. Like all insects, they use their sense of smell a lot.

What do they eat?

Adult flies often drink nectar. Some feed on any liquid that has nutrients. They also can "spit" onto dry food and then suck up the spit and some extra nourishment from the dry food. This is how they contaminate human food. Some female flies drink vertebrate blood, such as from mammals to get the protein they need for their eggs. A few adults are predators, they grab other insects, stab them with their mouthparts and suck out their blood and organs.

Many flies do most of their feeding as larvae. Some eat fungi or plants, especially fruit. Some lay their eggs in the stems or leaves, and they larvae give off chemicals that make the plant swell up into a gall. This protects the fly larva and gives it plenty to eat. Other species eat dead animals, and many eat dung. Some filter microscopic food particles from freshwater water. One big group of flies is parasitic. They lay their eggs inside or on insects and spiders, and the larvae feed on the inside of their host while it is still alive! A few species are parasites of vertebrates, such as mammals and birds, and get in wounds or under the skin.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
    • eats non-insect arthropods
  • herbivore

What eats them and how do they avoid being eaten?

Adult flies avoid predators with their speed and alertness. Also, many flies mimic stinging insects such as wasps or bees, so predators will avoid them. Larvae often live in places that are hard to reach.

What roles do they have in the ecosystem?

Some flies are imporant pollinators. Many fly larvae are part of the natural 'clean-up squad', helping get rid of dung and dead animals. Flies are important food sources for many other animals.

Do they cause problems?

True Flies are the worst insect pests. Some bite us, some spoil our food, some carry diseases.

How do they interact with us?

The biggest benefit from flies comes from the parasitic species. They attack caterpillars, grasshoppers, and other insects that eat our food plants. Some flies also help pollinate plants that we grow. Flies are also important food source for other animals that we value, like fish.

Are they endangered?

Very few fly species need conservation. The few that do live in rare habitats that are in danger.

  • IUCN Red List [Link]
    Not Evaluated

Some more information...

Insects that are True Flies have their name in two parts: House Fly, Flower Fly, etc. But some other kinds of insects are called "flies" even though they aren't related to the True Flies. They should have the "fly" part of their name attached to the previous part. For example: Dragonfly, Damselfly.



Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map


living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.


helps break down and decompose dead plants and/or animals


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


mid-altitude coastal areas with mild, rainy winters and long, dry summers. Dominant plant types are dense, evergreen shrubs.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


Having one mate at a time.


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


found in the oriental region of the world. In other words, India and southeast Asia.

World Map


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.


Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Climbing plants are also abundant. There is plenty of moisture and rain, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


remains in the same area


offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


lives alone


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


this biome is characterized by large expanses of coniferous forest, there is an extended cold season and heavy snowfall.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


A terrestrial biome found in very cold places -- either close to polar regions or high on mountains. Part of the soil stays frozen all year. Few kinds of plants grow here, and these are low mats or shrubs not trees. The growing season is short.

University of Michigan Museum of ZoologyNational Science Foundation

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. "Diptera" (On-line), Animal Diversity Web. Accessed April 23, 2014 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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