25 Interesting Fly Facts

By Karin Lehnardt, Senior Writer

Published January 4, 2023

There are over 100,000 types of flies._[9]
Horseflies and mosquitoes are both types of flies. The females of these fly species drink blood._[9]
Flies in cities carry more pathogens than flies in rural areas._[2]
Houseflies can transmit at least 65 serious diseases, including dysentery, leprosy, cholera, yaws, stomach ulcers, and typhoid fever._[2]
Together, the housefly and blowfly carry over 600 different types of bacteria. The housefly carries 351 types of bacteria. The blowfly carries about 316._[1]

Flies vomit on food they land on, leaving behind traces of what they have eaten before, such as sewage or feces

When a fly lands on a food source, like your lunch, it vomits. The acids in the vomit dissolve food so the fly can suck it up._[7]
Some flies, such as screw flies and botflies, can lay eggs in unbroken skin. The eggs develop and eventually burst through the host's skin as a full-grown fly._[9]
The term "fly" refers to over 125,000 species of dipterans, or "true" flies, which are found around the world, even in the subarctic and high mountains._[10]
The word "fly" can refer to gnats, midges, mosquitoes, leaf miners, horseflies, houseflies, blowflies, bee flies, and robber flies._[10]
While dragonflies, caddisflies, and mayflies may seem like flies, their wing structures are different, and they are not considered true flies._[10]
Mature houseflies live between 15–25 days. Some have been recorded as living up to two months._[9]
A female fly can lay up to 2,000 eggs in just one month. It takes just 10 days for the eggs to fully develop. Their rate of reproduction increases during warm weather._[7]
A fly's eyes have thousands of tiny lenses called ommatidia. These eyes allow flies to see 360 degrees at once._[9]

If you took a fly to a movie, the images would seem like a slow-moving slide show rather than the smooth movie we experience

There are two main types of flies: the Nematocera (which includes mosquitos and non-biting flies) and the Brachycera (which includes houseflies, fruit flies, and horseflies)._[7]
Unlike other insects, houseflies have only one set of wings with a membrane. Their second set of wings is reduced and is used for balance._[9]
Flies have a sensory system that helps them find exposed skin, which explains why they fly so close our faces and hands._[6]
Houseflies do not hibernate, but they spend the winter in diapause, which is a hibernation-like state of reduced metabolic activity. When the weather warms up, they emerge in full force._[9]
While male horseflies feed on nectar, female horseflies feed on both nectar and blood. Horseflies prefer feeding on large, dark-colored animals like horses, but they will also bite humans with their serrated mouthparts._[11]
Fruit flies' brains have about 200,000 neurons and other supportive cells, such as glia. By comparison, a human brain has 86 billion neurons. Even though fruit flies' brains are simple, they are still complex enough to do as much processing as a supercomputer._[5]

Flies aren't all bad

Flies are important pollinators and composters. They are also a good source of food for frogs, lizards, spiders and birds._[7]
Flies are most active when the temperature is between 80–90 degrees Fahrenheit._[7]
Flies do sleep. Before sunset, they try to find a safe place to sleep, such as underneath leaves, branches, or rocks._[9]
Each foot of a fly has two fat footpads with tiny adhesive hairs with spatula-like tips. The hair produces a glue-like substance that allows the fly to stick to ceilings and leaves behind sticky little footprints._[8]
Flies, especially fruit flies, experience something like pain, called "nociception." They can also experience chronic pain after an injury has healed._[3]
Before they act, flies appear to "think," and the more difficult the decision, the longer the fly thinks._[4]