What Are Black Fly Bites? 101 Guide

Have you ever heard of black fly bites1? Here, you will get all the information on the signs, symptoms, and cures in that case.

What are Black Flies?

Black flies, also known as buffalo gnats or turkey gnats, are small and humpbacked, usually black or dark gray. They have stout antennae and legs, gauzy wings, and a short mouth used for sucking blood.

These biting flies can crawl into boots, sleeves, and other vulnerable places. There are more than 1700 black fly species, in the world, with just 255 in North America.

More than males, female biting flies are more common, which might even kill birds, chickens, and domestic animals. Some have parasites that can cause Onchocerciasis (resulting in blindness or nodules under the skin.)

Let us look at these fly bites in detail.

Big black flies on the attack

1) Black Fly Bites

More specifically, these biting flies range from 5 to 15 millimetres (the size of adult black flies). They have short antennae, an arched thoracic region, and broad fan-shaped wings. A black fly larva grows around bodies of water.

Black fly bites are more common around the eyes, scalp, ears, and even exposed arms and legs, which can cause:

  • Swelling
  • Soreness
  • Numbness

Black fly bites can cause harm to animals and humans, by using scissors-like mouthparts to make holes in the skin, which may cause severe allergic reactions.

Pain, blood, and swelling occur as the body responds to the fly’s saliva.

1.1) Can Black Fly Bites Cause Black Fly Fever?

Black fly bites with many symptoms involving headache, nausea, swollen lymph nodes2, and fever, known as ‘black fly fever.’

1.2) Can Black Fly Bites Cause River Blindness?

Black fly bites also cause the disease – river blindness in countries like Africa and South America. This happens when they transmit a parasitic nematode worm that infects humans.

1.3) How Common Are Black Fly Bites?

Only six black fly-biting species feed on humans (eastern North America). Other species do not bite but are attracted to humans.

These can, however, fly and crawl into the ears, nose, eyes, or mouth, causing general annoyance.

1.4) Season Of Black Fly Bites

Although found all over the U.S., the impact of black fly bites depends on a specific region and time. In the Northeast and Upper Midwest, their bites are too extreme, from late spring to early summer, which can prevent activities like fishing and hiking.

Close-up of a black fly on a green leaf
From UnlimPhotos

1.5) Can Black Fly Bites Infect Livestock?

A black fly bite can also be a threat to livestock in the following ways:

  1. Transmitting disease agents like protozoa and nematode worms.
  2. Causing suffocation by crawling into the throat and nose of pastured animals.
  3. In extreme fly bite cases, they can also cause exsanguination (death due to blood loss).
  4. Typically bite injected with saliva can also cause a condition – toxic shock, which can lead to the death of livestock and poultry.

1.6) What Are The Different Types Of Black Flies?

The flies have 255 species with 11 identified genera (North America), 12 documented ones in Illinois, and over 30 in Minnesota and Wisconsin. However, many black fly species are yet to be discovered and identified.

1.7) How Long Do These Flies Live?

These flies develop as ‘complete metamorphosis‘ (a larval development where a nonfeeding pupal develops into a winged adult). Females develop a batch of almost 500 eggs after blood meals.

Mostly the eggs hatch between 4-30 days, with different larval stages varying from 4-7. Water and food supply are some of the factors that affect their development.

The adult flies can live for many weeks, primarily active between mid-May to July. Some may have just one generation while others have many, depending on certain factors.

1.8) What Are Their Feeding Habits?

Many species, specifically females, feed on mammals and birds. Not a single one feeds exclusively on humans, and the male flies are not attracted, nor are they biting flies.

These flies feed during the day, biting on the upper body and head. Unlike other species of flies, they do not enter human structures for their meals.

1.9) How Can These Flies Increase?

Some man-made structures like building concrete dams and stream channels might increase their numbers, as these act as developmental sites for their larvae and pupae.

The restoration of polluted streams is another cause, as the dissolved oxygen content has increased in streams, creating another suitable habitat for these flies.

1.10) How To Control Black Fly Bites?

A close up shot of a mosquito bite on a young boy's cheek
From UnlimPhotos

There are different methods one can try to control these flies:

1) Aerial applications of insecticides or physically altering their habitat.

2) Involving state agencies or professional pest control organizations. (However, this might not last long as females can travel long distances and re-infest in treated areas once the effect wears off.)

3) If you have to go outside, apply insect repellent that contains DEET.https://www.epa.gov/insect-repellents/deet

4) Minimize clothing with holes, or wear protective clothing (try to avoid dark-coloured clothing).

5) Other measures can include fine mesh head nets, like those worn by beekeepers, and wearing a light-coloured long-sleeved shirt and long pants.

1.11) How To Treat A Black Fly Bite?

  • To treat their bites, clean and apply topical products to reduce itching. It is best to avoid scratching to reduce the chances of infection.
  • You can also apply ice or a cool compress to the area in fifteen-minute intervals to reduce swelling. Cortisone or other prescribed topical steroids can also work.
  • Do not forget to wash the area with soap and water, which can significantly reduce the risk of infection.

2) Other Biting Flies

America has six major biting flies (including black flies). They have many variations which might not bite and be of no harm, but some can transmit diseases and cause allergic reactions.

2.1) Biting Midges

Biting midges are small in size, around 1/32 of an inch, due to which they can easily get into window and door screens. They are also called punkies and gnats.3

Symptoms of Biting midges: They are commonly found in North America, with bites resembling small red welts. It might be itchy as well.

Everywhere else, biting midges can transmit worms to humans inside the skin. This can create skin conditions like dermatitis and lesions.

Treatment of Biting midges:

  • Scratching the bites of biting midges is to be avoided.
  • Treatment involves topical steroids or cortisone, as prescribed by your doctor.
  • You can also apply aloe vera for natural remedies.

2.2) Stable Flies

Their size is similar to house flies but more minor, around 5-7 millimetres. Stable flies are found mainly around livestock. New Jersey, Tennessee Valley, and Florida are some of the places where they bite humans.

Bites of stable flies, which feel like needle pricks, have symptoms occurring in ankles, feet, and legs. You can see small and raised red bumps and red rashes.

For treatment, Benadryl can reduce swelling, hives, and itching. Naturally, you can apply ice to the bites to reduce pain.

2.3) Deer Flies

These are medium-sized flies (1/4 – 1/2 inch long), having transparent wings and brownish-black bands. Deer flies are most active during spring, found near lakes and swamps.

Deer fly bites can cause painful welts or red bumps. Deer flies are also known to transmit diseases of a bacterial kind – rabbit fever, which includes side effects like fever, skin ulcers, and headache.

For treating wounds, antibiotics suggested by a doctor are better. Firstly, clean the harmed area with soap and water, then apply ice to treat the pain.

Allergy medicine like Benadryl is helpful in reducing itching and any other infections caused by deer flies.

2.4) Horseflies

Horseflies are large, with green heads and a full black appearance. They are commonly found near water, and other wet, warm locations.

Horseflies have painful bites, which can cause itchiness, inflammation, swelling, and a bruise. But, it cannot transmit diseases.

Although more harmful for horses, one can take treatment like cleaning the bite and applying an antiseptic ointment or spray. Usually, it heals after a few days, but consult a doctor if any unusual symptoms occur.

2.5) Sand Fly 

Sandflies are tiny and worm-like (1/8 of an inch), usually having brownish to grey wings.

Sandflies are found mostly in tropical and subtropical climates. They are most prevalent in the Southern U.S. Breeding occurs in places having moistures like decaying plants, mud, and moss.

Female sand flies are the ones who feed on animal and human blood. Generally, they eat nectar and sap.

Symptoms of Sandfly bites: These biting flies leave painful bites that can cause blisters and red bumps. If infected, they further lead to skin inflammation4.

Biting flies of these kinds can also transmit diseases like leishmaniasis (parasitic disease), which is rare in the US, and more prevalent to contract during foreign travels.

Symptoms might include skin sores (weeks – months.) No vaccination is present for this. 


Black fly bites as irritating as they are, can clear out on their own. But, if it is serious, it is better to get medical treatment.

You can simply apply calamine lotion to reduce itching. Aloe vera and oatmeal baths can also be applied as natural remedies. 

Check this out to learn how to prevent and control a harmful fly situation.

If you liked this article, click here to read another interesting article on flies. 

All You Should Know About 5 Common Bug Bites
Icy Health
  1. Gudgel, EDWARD F., and FRANKLIN H. GRAUER. “Acute and chronic reactions to black fly bites (Simulium fly).” AMA Archives of Dermatology and Syphilology 70.5 (1954): 609-615. ↩︎
  2. Willard-Mack, Cynthia L. “Normal structure, function, and histology of lymph nodes.” Toxicologic pathology 34.5 (2006): 409-424. ↩︎
  3. Schwab, Peter J. “Imps of the wilderness.” Field & Stream (West ed.) 103.3 (1998): 100-102. ↩︎
  4. Pasparakis, Manolis, Ingo Haase, and Frank O. Nestle. “Mechanisms regulating skin immunity and inflammation.” Nature reviews immunology 14.5 (2014): 289-301. ↩︎

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