Black fly
Small flies that bite and spread river blindness.
Black flies (or blackflies), sometimes called buffalo gnats, turkey gnats, or white socks, are flies in the family Simuliidae of the Culicomorpha infraorder. Over 2,200 species have been formally named, of which 15 are extinct. They are divided into two subfamilies: Parasimuliinae, containing only one genus and four species, and Simuliinae, containing all the rest. Black flies are usually small, black or gray, with short legs and antennae. They are a common nuisance for humans and spread several diseases, including river blindness in Africa and the Americas.
- field
- Entomology
- known_for
- Biting pests that spread river blindness; nuisance to humans and livestock
- species_described
- Over 2,200
- extinct_species
- 15
- subfamilies
- Parasimuliinae and Simuliinae
- type_genus
- Simulium
Lore & Background
Black flies lay eggs in running water, and larvae attach to submerged rocks using tiny hooks and silk holdfasts. They have foldable fans around their mouths that catch passing debris for food. Larvae pupate underwater and emerge as flying adults in a bubble of air. Some South African species' larvae are phoretic on mayfly nymphs. Adult males and females feed on nectar or honeydew for energy, but females of most species also bite birds or mammals to obtain blood for egg production. Males cannot bite through skin. Different species prefer different hosts, and they feed in the daytime, especially when wind speeds are low. Some African species can range up to 40 miles from breeding sites.
Reader's Guide
Black flies are significant as both a nuisance and a vector of disease. They are a common pest for humans in many regions, including parts of Canada, New England, Upstate New York, Minnesota, and the Upper Peninsula of Michigan, where populations swell from late April to July. They also affect livestock, causing weight loss in cattle, and the saliva of one species can cause anaphylactic shock. The Blandford fly in England was a public health problem until controlled by Bacillus thuringiensis israelensis. Black flies are central to the transmission of Onchocerca volvulus, which causes river blindness, endemic in parts of South America, Africa, and the Arabian Peninsula. Control efforts are complicated by their ability to disperse tens or hundreds of miles. Repellents containing DEET, picaridin, or IR3535 provide some protection, but additional measures like netting and protective clothing are often needed.
Did You Know?
- Black fly larvae use tiny hooks at the ends of their abdomens to hold on to submerged rocks.
- The Blandford fly (Simulium posticatum) in England was controlled by targeted applications of Bacillus thuringiensis israelensis.
- Black flies are the vector for the parasitic nematode Onchocerca volvulus, which causes river blindness.
Frequently Asked Questions
What is a black fly?
A black fly is a small biting insect in the family Simuliidae, part of the Culicomorpha infraorder. They are also commonly called buffalo gnats, turkey gnats, or white socks depending on the region.
How many black fly species exist?
More than 2,200 species have been formally described, though 15 of those are now confirmed extinct. Taxonomically they fall into two subfamilies: Parasimuliinae, which holds a single genus and four species, and Simuliinae, which encompasses the rest.
What diseases do black flies spread?
Female black flies are the primary vectors for river blindness (onchocerciasis), a parasitic condition that affects humans in parts of Africa and the Americas. They also cause widespread nuisance biting for people and livestock.
What do black flies look like?
Most species are small and dark—typically black or gray—with notably short legs and antennae. Their compact, stocky build sets them apart from mosquitoes and other similar-looking biting flies.
Why are black flies important to entomology?
They are a major research focus because of their role in transmitting river blindness and their broad impact on human and animal health. With over 2,200 described species, they also offer a rich subject for taxonomic and ecological study.
More in Invertebrates 1-24
Elsewhere in the Invertebrates universe
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record