- Houseflies: Houseflies are the most common fly in the United States, and can also be found in basically any type of home worldwide. These insects are grayish in color, with four black stripes on their thorax. Adult houseflies range from between 1/8 inch and 1/4 inch long, and their bodies are somewhat hairy. Up close, they have distinct compound eyes, which are red in color and contain thousands of individual lenses, giving them a huge field of vision. Housefly eggs, meanwhile, are extremely small—think roughly the size of a grain of rice. Eventually, they hatch into larvae, or maggots, which are cream-colored and have a greasy look to them. In this state, they can reach about 1/4-3/8 of an inch long, before they enter the pupal stage, where they develop dark, hard exteriors, which they eventually shed before becoming full-grown adults.
Depending on conditions, a housefly can grow from an egg to a full-grown adult in about six days. It is common to find eggs in a variety of nasty places, such as on feces, near rotted food, or in the trash can. While female houseflies usually only mate once, they are capable of producing between 350 and 900 eggs in their lifetime. They do not have teeth and are not stinging insects, instead feeding on liquids, using their spongey mouthparts to actually liquify solid foods. Their favorite foods include everything from human leftovers to garbage to animal waste.
To reiterate, houseflies do not bite, though they are capable of carrying more than 100 pathogens that can be transferred to humans. These include diseases such as salmonellosis, typhoid, and tuberculosis. As a result, a housefly merely landing on a food surface can contaminate it, as they pick up biological organisms and spread disease through both their mouths and legs. They also defecate wherever they land, which in turn spreads more bacteria. This is why even one fly can represent a cleanliness issue for your household—and a lot may merit professional extermination.
- Fruit Flies: The fruit fly is another variety of this insect that can be found throughout the United States and which, like their cousin the housefly, is capable of reproducing extremely quickly, with females laying up to 500 eggs at a time that can begin to hatch in as quickly as 24 hours. They have a longer lifespan than houseflies however, generally living anywhere from 25 to 30 days, in contrast to the 15-25 days most houseflies survive for. Their bodies are extremely small, ranging from 3 to 4 mm long, with a brown or tan color. Although you may not be able to see it, they have red eyes and oval-shaped antennae.
As their name suggests, fruit flies are naturally attracted to rotting food matter, and are particularly keen on fruit and vegetables. They also love any kind of fermented or fermenting liquids, such as beer, wine, and liquor. These insects like to hang out and breed in the dark, and are often found in dank, dirty environments like drains, garbage disposals, and trash cans. Like other fly species, they have a four-stage life cycle, which may be finished in a week, depending on various conditions.
In addition to being huge nuisances, fruit flies can also contaminate your food with a number of bacteria and pathogens. Much like houseflies, they thrive in unsanitary conditions, so it is extremely important to keep your home tidy if you want to keep them away—and especially to throw away any fruit ASAP when it starts to rot.
- Horseflies: While the origin remains somewhat apocryphal, the common assumption is that horseflies got their name from their tendency to bother horses and other animals. These insects can be found in a range of areas, both rural and suburban, but are especially drawn to bodies of water, where mammals are typically abundant and conditions are ideal for breeding. You may be able to recognize a horsefly by its gray or blackish body, which is distinctly smaller than other types of flies, usually measuring just 10-30 mm long. Though you probably won’t be able to see it, their eyes have a green or purplish color, and they have stout bodies with six legs and short antennae.
One of the hallmarks of the adult horsefly is that it is extremely fast, with the ability to travel more than 30 miles outside of their birth site (though this does not happen often.) Unlike fruit flies, they are attracted to light, and often gather around windows. However, you may also see them in open wooded paths, where they will wait for potential hosts. It is extremely common to see them on windless, sunny days, especially if you are near wet soil or a body of water. Of the most common American flies, they also have the longest lifespan, surviving anywhere from 30-60 days depending on conditions.
While horseflies are not known for being vectors of disease or spreaders of bacteria (at least not in humans,) females do bite, as their mouthparts are used to suck up blood for sustenance. They are also exceptionally persistent, and will continue to attack a host until they are fed or killed. Some females horseflies will even chase their targets, following them from one location to the next. And while their bites generally aren’t harmful to humans, they cause painful allergic reactions, so it is important to get them exterminated ASAP for the sake of yourself and your animals.