Types of Flies for Fly Identification

picture of the eyes of a horse fly

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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.

Notwithstanding the pest label, many fly families can be considered as beneficial insects that pollinate plants and prey on insect pests. This brief presentation provides pictures and descriptions of some basic fly types to help answer beginning fly identification questions.

Bee Flies

picture of a bee fly in the paravilla genus

Speaking of mimics, they abound in the world of flies. The fuzzy bodies of bee flies (family Bombyliidae), for example, explains their nickname. Like bees, many Bombyliidae are natural pollinators that nectar on flowers.

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.

How to Identify Flower Flies

picture of a flower fly.

A group of flies commonly called flower flies and technically called syrphid flies get characterized 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 thoracic and abdominal 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.

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).

Tachinid Flies

picture of a red tachnid fly.

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.

Horse Flies

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.

Robber Flies

picture of a robber fly

Robber flies remain interesting to the insect enthusiast based on the fact that they are one of only a few predatory fly families that feed on other insects. One of the first tips for identifying robber flies is to be on the watch for them as they 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.

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 robber fly appearances show similarities from species to species. Primarily they are large, aggressive flies with thin, long bodies. There are some exceptions, with a few species having a more rounded appearance and resembling bumblebees.

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.

Soldier Flies

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 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.

© 2005-2016 Patricia A. Michaels