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Facts About Black Flies

Black flies (Simuliidae) are also commonly known also as "buffalo gnats", "white socks", and "turkey gnats". There are over 2,200 known species of Black flies. These nuisance flies are small, pudgy creatures, known for swarming around and annoying wildlife, poultry, livestock, and even humans. Learn more about Black flies so that you can better know how to deal with them and get rid of them.

Black flies

What Do Black Flies Look Like?

Black flies are small flies (smaller than Houseflies), rounded in shape, measuring 1/5" to 1/3" in length, and ranging in color from dark grey to black. They feature a distinct "hump-like" body, as well as noticeably short legs, one set of wings, and reddish eyes.  

Where do Black Flies Come From?

Black flies can be found in just about any region of the world, from the tropics to arctic areas, including in the United States and Canada.

A stray Black fly may occasionally find its way indoors, but these flies do not breed, develop, or infest indoor areas.

Black Fly Habits

Black flies are known to breed only in running water (streams, brooks, rivers, etc.), and the larvae attach themselves to rocks. Interestingly, females will NOT lay their eggs in polluted water. Some species prefer large, fast-flowing streams, while others opt for slower waters. In just about any kind of flowing waters, you will find some species or other of Black flies.

Black fly larvae feed on a vegetation-based diet, as well as on various underwater organisms, including mosquito eggs and larvae.

In the damper, northern parts of the U.S., as well as in Canada, especially in the mountains, Black fly populations are most prominent from late April to July, becoming a nuisance to those of us who engage in outdoor activities like hiking, camping, boating, fishing, and gardening.

In Spring 2020, hordes of Black flies were reported aggressively swarming and attacking individuals outdoors in the Minneapolis-St. Paul, Minnesota urban areas. It is reported that they had become incrementally more aggressive and "worse," starting in 2018.

Do Black Flies Bite?

Black flies do bite, and it is painful when they do. Male Black flies feed mostly on plant nectar, and as with other pest species (e.g., mosquitoes), it is the females that bite, in search of blood meals so they can lay eggs. Female Black flies feed during the day, usually biting mainly on the head and upper body.

The reason their bite is so painful is that the females cut and dig a hole into the skin so they can feed on the pooling blood. While feeding on blood, females inject a coagulant to help prevent the blood from clotting, and this is what many people and animals are actually allergic to.

Black fly bites can result in sickness, weight loss, and death for many domestic animals, especially poultry and pet birds. In the U.S., Black flies are not known to carry diseases, though the transmission of bacteria and blood contaminants is likely. Human deaths from Black fly bites have been reported, assumed to be caused by allergic reactions.

The Black Fly Life Cycle 

Females will deposit anywhere from 150 to 600 eggs in underwater vegetation, and the eggs will hatch in less than a week. The eggs develop through the larval and pupal stages in the water before emerging as adults. Black flies, in ideal (warmer) conditions), have relatively short lifespans that last no more than 2-3 weeks.

Depending on the species and on what area of the world you are in, one to six Black fly generations may be seen in a year. In cooler areas, Black fly larvae will overwinter until pupating in the spring, and in even colder parts of the world, the eggs will overwinter before hatching.  

How Do You Get Rid of Black Flies?

Pest Control Products

Since Black flies are mainly outdoor creatures, you don't need to worry much about managing them indoors.  

Try an effective plant oil-based indoor fly killer for spot-treatment, like Maggie's Farm Home Bug Spray, or Maggie's Farm Flying Insect Killer. Plants don't like flies and other bugs any more than you do, and the natural oils they produce to protect themselves are amazingly effective at killing and repelling bugs of all sorts. For effective personal protection against flies (and mosquitoes), try plant oil-based Maggie's Farm Natural Insect Repellent.

For longer term, more thorough coverage, you can treat wider areas of your lawn with effective hose-end plant oil-based pest control products like Maggie's Farm Yard Bug Spray

Always carefully follow any directions on pest control product labels, including for storage and disposal.

Find more information here:

The Best Indoor Fly Killer Spray

Tips for a Bug-free Cookout

How to Use a Yard Bug Spray

How to Keep Pests Out of Your Lawn Naturally

How to Prevent Overwintering Pests

Controlling Flies Outdoors

For scientifically-tested, effective fly control in your home that is friendly to the environment, try Maggie’s Farm pest control products. Our promise is that our plant and mineral-based products are developed by scientists and seasoned pest control professionals to be the most effective.

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