Types of Flies

Flies, insects in the order Diptera, from your basic house fly to mosquitoes and gnats, are defined by having two wings.

With over one hundred and fifty thousand Diptera species, divided into over one hundred families, a proper categorization of different types of flies would necessarily be an encyclopedic endeavor.

A less systemic approach to Diptera often begins by thinking about them in terms of their relationship to humans.

Many people, for example, want to know about poisonous flies. In fact, there are no poisonous flies in the sense that these insect produce and inject venom as do some spiders.

It's more accurate to think of flies as disease spreading pests that pick up bacteria and viruses from many different sources, and then spread those bacteria and viruses during the course of their every day existence. Mosquito transmission of West Nile virus for example, presents an ongoing challenge to public health officials.

Other flies such as horse flies, deer flies and snipe flies are rightly labeled as biting pests.

Notwithstanding the pest label, many fly families can be considered as beneficial insects that pollinate plants and prey on insect pests.

The video shows a tachinid fly, a wasp mimic, a common defense mechanism of a variety of fly species, including bee flies. Click on any of the links in the accordion for additional information and pictures of many types of flies common in North America.

picture of a pair of Bombylius bee flies, perhaps Bombylius major

The fuzzy bodies of bee flies (family Bombyliidae) explains their nickname.

Their resemblance to bees and/or wasps extends to some bee and wasp habits. For example, like bees, many Bombyliidae are natural pollinators that nectar on flowers.

Turning the tables on their physically similar counterparts, Bombyliidae larvae are parasitic on a variety of bee and wasp species.

However, unlike bees and wasps, Bombyliidae are not stinging or biting insects.

With approximately eight hundred North American species, Bombyliidae represent a fairly robust family that divides into multiple subfamilies and genera.

The top picture shows a member of the Bombylius genus, perhaps Bombylius major, the greater bee fly.

The fuzzy bee like body and sword-like proboscis represent the typical bee fly image.

picture of a bee fly in the thevenetimyia genus

The thin body of Thevenetimyia species distinguishes them from many of the round, buzzy, bee looking Bombyliidae species.

The approximately twenty different Thevenetimyia species can be found in many areas of western North America.

The picture shows a species enlarged by a factor of at least two, in order to highlight the body details. In person they appear as smallish flies.

picture of a bee fly in the paravilla genus

A few different bee fly genera have species with golden bodies.

The body color, along with the wing pattern provides clues to tentatively place the species in the third picture the Paravilla genus.

picture of a male midge fly

People often inquire into the types of flies that sting.

Of course, bees and wasps have stingers, and flies do not. Technically most people think of stinging flies as the biting flies.

Around the world, groups of flies get labeled as pests and medical pests because their bites transmit diseases. The tsetse fly fly, for example, a native African family of flies, are known for transmitting parasites known to cause sleeping sickness.

Closer to home, people easily forget that mosquitos are flies. Easier to remember are mosquito outbreaks combined with mosquito bites.

Health officials continue to warn populations about potential problems with mosquito outbreaks, especially as they relate to the spread of West Nile virus.

Mosquito control in residential areas can often be effectively implements by removing any stands pools of water, thereby preventing mosquito breeding.

Horse flies and deer flies often receive a good deal of attention due to the female's predatory nature. They inhabit most areas of the United States.

In other areas, specific flies cause specific problems. Florida, for example, has problems with sand flies. Colorado, on the other hand, has problems with black flies.

An application of DEET on the skin often serves as an effective repellent for most, if not all the native biting flies.

Two additional fly groups worth mentioning:

picture of a snipe fly in the Chrysopilus genus

Snipe flies (family Rhagionidae) (second picture) often can be found in wooded areas near water sources.

Long, thin abdomens and long legs serve as good field identification clues, although many species as so small that seeing the legs and abdomen can be difficult without an enlarged picture.

Most snipe flies are labeled as insect predators and a few species are biting pests akin to horse flies.

The term midge fly applies to a handful of Diptera families which are related to mosquitoes and black flies.

Often midge families get differentiated along biting and non-biting categories.

The top picture shows a non-biting species typically found in large numbers near fresh water environments during the spring.

The thin body and feathery antennae indicate a male.

The biting midges, Family Ceratopogonidae, can be found throughout most of North America and go by a variety of common names such as no-see-ums, sand flies and punkies.

The no-see-ums nickname is indicative of their diminutive size. The sand fly nickname is indicative of their fondness for coastal and other aquatic areas with sandy shores, although they are not related to the separate sand fly family, Phlebotomidae.

Found in most aquatic areas, biting midges are considered an annoyance, however they are not known to transmit disease.

picture of a Black horse fly

The name horse fly can apply to any species in the family Tabanidae, including deer flies, or the name can be more specifically applied to flies in the genus Tabaninae.

Tabaninae horse flies are known for their size, and the painful bite inflicted by females.

Horseflies often live near water environments, where their larvae feed and grow on the local insects and small fish. Thinking habitat suggests that North American horsefly populations increase in the Southeast and decrease in the Southwest.

Adults can grow over an inch in length, and females feed on blood from mammals, including humans, a practice that places them into the insect pest category. For humans at least, the use of over the counter insect repellents containing deet (N-diethyl-meta-toluamide) is usually sufficient to deter them during their season. (Note: deet is a strong chemical and it should only be applied according to the directions given on the container.)

A couple dozen different horse fly species inhabit forests and fields across North America. Apart from size, many horse fly species can be identified by their colorful eyes.

Eye configuration can also help determine gender. The eyes of male horseflies are set close together, female horse fly eyes have a space between them.

picture of a Western Horse Fly

Picture two shows the female Western Horse Fly (Tabanus punctifer), a common Western species where the female's colorful eyes are muted. The light colored patch of hair behind the eyes serve as an additional species field identification clue.

Not to be outdone by blandness, the top picture shows the Black Horsefly (Tabanus atratus), a very common Eastern species.

Regardless of the bland color of the body and eyes for both the males and females, at one inch in size, the Black Horse Fly can be a real nuisance.

picture of a robber fly, laphria astur

With around one thousand different species of Robber Flies (family Asilidae) in North America, there is a good chance you will find at least one species in your area.

Generally they are large, aggressive flies, that tend to have thin and long bodies. There are some exceptions, with a few species having a more rounded appearance and resembling bumblebees.

Robber flies are one of a few predatory fly families that feed on other insects. They tend to perch in an area of their territory, waiting for insects to approach. Once prey is spotted, they attack, using their proboscis to inject a neurotoxin into the prey.

Their ability to paralyze prey allows them to hunt for relatively large insects such as grasshoppers and dragonflies.

Fortunately their aggressive behavior does not extend to humans, making it easy to approach them and watch their behavior.

The first picture shows the Laphria astur robber fly. It is called a mimic fly. Its long thin abdomen resembles a wasp and its hair and coloring resemble a bumblebee.

The physical appearance enables them to approach bees without giving away their predatory intentions.

picture of a robber fly in the genus Callinicus

More than a handful of robber fly genera can be identified by the stripe pattern on the abdomen.

The gold and black abdominal and thoracic stripes on the robber fly in the second picture indicate a species in the genus Callinicus.

Callinus species can often be found at higher elevations along the West Coast.

picture of a robber fly called the hanging thief

One of the few robber fly genera to receive a common nickname, the hanging thief (Diogmites), is a fairly common species east of the Rocky Mountains.

The name derives from the fact that in addition to the usual robber fly perching position, they can often it can be found hanging by a couple of legs on a branch, or other support area, consuming their prey.

While a few other robber fly species sport green eyes, the green eyes and brown body serve as typical field identification clues for the approximately two dozen North American species.

Syrphid Flies (Syrphidae), a family of flies that includes hover flies, flower flies and bee mimics, inconspicuously inhabit most every corner of yards and fields across the United States.

Their often colorful bodies resemble bees and wasps, and like bees and wasps, their pollinating activities break the traditional fly mold and place them squarely in the beneficial insect category.

Gardeners and farmers have long celebrated syrphid flies as beneficial insects because their larvae consume aphids.

With over seventy five different genera and hundreds of species, identification of any one species can be difficult.

Syrphid identification involves matching thorasic and adominal patterns to a genus, and hopefully species.

With a few species, eye color and face color can be a good ID clues. A few species have a distinct hair pattern on the abdomen. In some cases, a close up of the wing pattern also helps.

The Syrphini tribe, probably the largest in the Syrphid fly family, consists of about twenty different genera.

The top picture shows one species from the Syrphus genus, the namesake for both the family and tribe. Syrphus populations abound along both North American coasts, making them some of the most common syrphid species in high population residential areas.

A rounded and distinctly patterned abdomen provide the first ID clues for all Syrphus species.

Eristalis, perhaps the best known of the syrphid fly genera, consists of over one dozen North American species.

The second picture in the top frame shows Eristalis tenax, a very common species, also known by the common name drone fly.

Drone flies can almost anywhere flowers grow. South of the border, Eristalis species continue to be documented.

One lesser known Eristalis fact... Microsoft co-founders Bill Gates and Paul Allen had Eristalis species named after them: Bill Gates' flower fly (Eristalis gatesi); Paul Allen's flower fly (Eristalis alleni).

In contrast, the picture on the right side of the page show three Syrphid species frome three different genera sharing the physical characteristic of thin, elongated bodies.

Allograpta micrura, the first image in the gourp, lives in western North America from Canada to Mexico.

The thin body and yellow spots at the bottom of the abdomen are good field identification clues.

Meliscaeva cinctella, picture two, is the sole representative of its genus in North America.

Specimens have been documented on both coast of the United States, including Alaska. There is also a European population.

Sphaerophoria, a long name for a genus of often small, thin syrphid flies, consists of some sixteen different species.

Sphaerophoria body patterns change from male to female as well as among the species.

A few additional syrphid genera, Toxomerus, for example, also are characterized by their diminutive size and thin bodies.

Parasitism, a reproductive strategy not typically associated with flies, serves as a key trait uniting the large and diverse fly family Tachinidae, better known as tachinid flies.

With a world wide distribution of some ten thousand species, the tachinids have been loosely organized according to common parasitic strategies along with common physical traits.

For example, the smallest subfamily of Tachinidae, the Phasiinae, usually get classified as the least hairy tachinids that parasitize true bugs (order Heteroptera).

Entomologists generally converge on the idea that most Tachininae species, along with other tachinids, adopt a parasitic reproductive strategy that targets members of the Lepidoptera order, butterflies and moths, as the host for their larvae.

Furthermore, because so many moth larvae are classified as agricultural pests, tachinids that parasitize them often get classified as beneficial insects. The use of tachinid flies to control gypsy moth infestations of forests serves as one of the most prominent examples of their use as biological control agents.

The proven and potential utility of Tachinidae gives them a prominent place in present and future entomological research.

North America hosts over five dozen different tachinid genera. As a rule of thumb, tachinids can be identified by their hairy and/or colorful abdomens.

picture of a bottle fly

The blue bottle fly, a species of Blow Fly in the family Calliphoridae, mostly feeds on dead animals.

Bottle Flies come in many metallic colors such as blue, green, copper or black.

picture of a Crane Fly

The long legs and thin bodies of crane fly species (family Tipulidae) make them among the easiest members of the Diptera to identify at the family level.

With approximately fifteen hundred North American species, moving beyond identification at the family level can be problematic. Estimates of the number of species world wide vary, but with over ten thousand different species, the Tipulidae rank as the largest fly family (Diptera).

While species vary in size, some of the larger species (over two inches in length) also rank as the world's largest flies.

Crane flies go by a variety of nicknames, including mosquito hawk, although adults do not feed on mosquitoes. They also do not bite humans. In some areas they are called daddy long legs.

picture of a flesh fly

Flesh Flies (Sarcophagidae family) produce larvae that feeds on animal flesh.

They are common flies, with close to four hundred different species found in the United States. The red eyes, black stripes on the thorax and checkered body are characteristic of species.

small-headed fly picture

Small-headed flies (Acroceridae family) go against the grain of stereotypical fly behavior.

Unlike many other fly families, most adult small-headed flies are flower feeders. They are known for their extended proboscis. The above picture partially shows the proboscis reaching to the bottom of the flower for nectar.

Juvenile or larvae small-headed flies display equally remarkable behavior. They are carnivores, of spiders no less. Adults usually lay eggs near spider habitat. Young larvae hop on passing spiders, burrow inside, and proceed to feed on the spider.

picture of a longlegged fly

The longlegged flies are members of the Dolichopodidae family. One look at the above picture explains its name.

Generally, they are small flies, maybe half the size of the average house fly. They have a metallic color body that sits on a long set of legs.

You can see them on leaves in many areas near water.

picture of a soldier fly

Soldier Flies belong to the family Stratiomyidae. They come in a variety of colors, often with stripes or multicolor abdomens. Many species resemble bees or wasps.

This green soldier fly in the top picture looks almost good enough to eat. That's probably not a good idea because they sometimes feed on manure.

They are not considered pests.

picture of a thick-headed fly

The picture explains the thick-headed flies (Conopidae) name. Their heads are generally wider than their bodies.

They are also sometimes called wasp flies because their thin waist gives them a resemblance to wasps.

Most Conopidae species are, on average, larger than horse flies and smaller than wasps. They can often be found nectaring on flowers.

picture of a Muscid fly in the Thricops genus

Fortunately orange flies are few and far between, making identification of a species in the Thricops genus relatively straight forward.

They belong to the larger Family Muscidae of house flies and kin, and inhabit areas of the West Coast.

© 2005-2014 Patricia A. Michaels