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A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the
Culicomorpha The Culicomorpha are an infraorder of Nematocera, including mosquitoes, black flies, and several extant and extinct families of insects. They originated 176 million years ago, in the Triassic period. There are phylogenetic patterns that are used ...
infraorder. It is related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. Over 2,200 species of black flies have been formally named, of which 15 are extinct. They are divided into two subfamilies:
Parasimuliinae The Parasimuliinae are a subfamily of Simuliidae (black flies) containing only one genus and four species. Most species are rare, and some are cave dwellers, in western North America. Species * Genus ''Parasimulium'' Malloch, 1914 :* Subgen ...
contains only one genus and four species;
Simuliinae Simuliinae is a subfamily of black flies (Simuliidae). It contains over 2,200 species, with over 1,800 of them in the genus ''Simulium ''Simulium'' is a genus of black flies, which may transmit diseases such as onchocerciasis (river blin ...
contains all the rest. Over 1,800 of the species belong to the genus ''
Simulium ''Simulium'' is a genus of black flies, which may transmit diseases such as onchocerciasis (river blindness). It is a large genus with several hundred species, and 41 subgenera. The flies are pool feeders. Their saliva, which contains anti ...
''. Most black flies gain nourishment by feeding on the
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
of mammals, including humans, although the males feed mainly on nectar. They are usually small, black or gray, with short
legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element c ...
, and antennae. They are a common nuisance for humans, and many U.S. states have programs to suppress the black fly population. They spread several diseases, including river blindness in Africa (''Simulium damnosum'' and ''S. neavei'') and the Americas (''S. callidum'' and ''S. metallicum'' in Central America, ''S. ochraceum'' in Central and South America).


Ecology

Eggs are laid in running water, and the
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...
e attach themselves to rocks. Breeding success is highly sensitive to water pollution. The larvae use tiny hooks at the ends of their abdomens to hold on to the substrate, using silk holdfasts and threads to move or hold their place. They have foldable fans surrounding their mouths. The fans expand when feeding, catching passing debris (small organic particles, algae, and bacteria). The larva scrapes the fan's catch into its mouth every few seconds. Black flies depend on lotic habitats to bring food to them. They will pupate under water and then emerge in a bubble of air as flying adults. They are often preyed upon by trout during emergence. The larva of some South African species are known to be
phoretic Phoresis or phoresy is a non-permanent, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to another (the host) solely for the purpose of travel. Phoresis has been observed directly in ticks and mites s ...
on mayfly nymphs. Adult males feed on nectar, while females exhibit anautogeny and feed on blood before laying eggs. Some species in Africa can range as far as from aquatic breeding sites in search of their blood meals, while other species have more limited ranges. Different species prefer different host sources for their blood meals, which is sometimes reflected in the common name for the species. They feed in the daytime, preferably when wind speeds are low. Black flies may be either univoltine or multivoltine, depending on the species. The number of generations a particular pest species has each year tends to correlate with the intensity of human efforts to control those pests. Work conducted at Portsmouth University in 1986–1987 indicates ''Simulium'' spp. create highly acidic conditions within their midguts. This acidic environment provides conditions ideally suited to bacteria that metabolise cellulose. Insects cannot metabolise cellulose independently, but the presence of these bacteria allows cellulose to be metabolised into basic sugars. This provides nutrition to the black fly larvae, as well as the bacteria. This symbiotic relationship indicates a specific adaptation, as fresh-flowing streams could not provide sufficient nutrition to the growing larva in any other way.


Regional effects of black fly populations

* In the wetter parts of the northern latitudes of
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
, including parts of
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
,
New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces ...
,
Upstate New York Upstate New York is a geographic region consisting of the area of New York (state), New York State that lies north and northwest of the New York metropolitan area, New York City metropolitan area. Although the precise boundary is debated, Upsta ...
,
Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over t ...
, and the Upper Peninsula of Michigan, black fly populations swell from late April to July, becoming a nuisance to humans engaging in common outdoor activities, such as gardening,
boating Boating is the leisurely activity of travelling by boat, or the recreational use of a boat whether powerboats, sailboats, or man-powered vessels (such as rowing and paddle boats), focused on the travel itself, as well as sports activities, suc ...
,
camping Camping is an outdoor activity involving overnight stays away from home, either without shelter or using basic shelter such as a tent, or a recreational vehicle. Typically, participants leave developed areas to spend time outdoors in more nat ...
, and backpacking. They can also be a significant nuisance in mountainous areas. * Black flies are a scourge to livestock in Canada, causing weight loss in cattle and sometimes death. *
Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
operates the largest single black fly control program in North America. The program is seen as beneficial to both the quality of life for residents and to the state's tourism industry. * The Blandford fly (''Simulium posticatum'') in England was once a public health problem in the area around
Blandford Forum Blandford Forum ( ), commonly Blandford, is a market town in Dorset, England, sited by the River Stour about northwest of Poole. It was the administrative headquarters of North Dorset District until April 2019, when this was abolished and it ...
, Dorset, due to its large numbers and the painful lesions caused by its bite. It was eventually controlled by carefully targeted applications of ''
Bacillus thuringiensis israelensis ''Bacillus thuringiensis'' serotype ''israelensis'' (Bti) is a group of bacteria used as biological control agents for larvae stages of certain dipterans. Bti produces toxins which are effective in killing various species of mosquitoes, fu ...
''. In 2010, a summer surge of insect bites blamed on the Blandford fly required many who had been bitten to be treated in a hospital. * The New Zealand "sandflies" are actually black flies of the species '' Austrosimulium australense'' and '' A. ungulatum''. * In parts of Scotland, various species of black flies are a nuisance and bite humans, mainly between May and September. They are found mainly in mixed birch and juniper woodlands, and at lower levels in pine forests, moorlands, and pastures. Bites are most often found on the head, neck, and back. They also frequently land on legs and arms. * In
Peninsular Malaysia Peninsular Malaysia ( ms, Semenanjung Malaysia; Jawi: سمننجڠ مليسيا), or the States of Malaya ( ms, Negeri-negeri Tanah Melayu; Jawi: نڬري-نڬري تانه ملايو), also known as West Malaysia or the Malaysian Peninsula, ...
35 species of preimaginal black flies were discovered in a study in 2016, including ''Simulium digrammicum'', which had been considered locally extinct.


Public health

Only four genera in the family Simuliidae, ''
Simulium ''Simulium'' is a genus of black flies, which may transmit diseases such as onchocerciasis (river blindness). It is a large genus with several hundred species, and 41 subgenera. The flies are pool feeders. Their saliva, which contains anti ...
'', ''
Prosimulium ''Prosimulium'' is a genus of black flies (insects in the family Simuliidae A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. It is r ...
'', ''
Austrosimulium ''Austrosimulium'' is a genus of 31 species of black flies that are distributed in Australia and New Zealand. There are 2 subgenera: '' Austrosimulium'' whose species are principally from New Zealand, and '' Novaustrosimulium'' which are exclusi ...
'', and ''
Cnephia ''Cnephia'' is a genus of 9 species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of org ...
'', contain species that feed on people, though other species prefer to feed on other mammals or on
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
. ''Simulium'', the type genus, is the most widespread and is a vector for several diseases, including river blindness. Mature adults can disperse tens or hundreds of miles from their breeding grounds in fresh flowing water, under their own power and assisted by prevailing winds, complicating control efforts. Swarming behavior can make outdoor activities unpleasant or intolerable, and can affect livestock production. During the 18th century, the "Golubatz fly" (''Simulium colombaschense'') was a notorious pest in central Europe. Even non-biting clouds of black flies, whether composed of males or of species that do not feed on humans or do not require a blood meal before egg laying, can form a nuisance by swarming into orifices. Bites are shallow and accomplished by first stretching the skin using teeth on the labrum and then abrading it with the
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...
e and mandibles, cutting the skin and rupturing its fine capillaries. Feeding is facilitated by a powerful
anticoagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where t ...
in the flies'
saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can ...
, which also partially numbs the site of the bite, reducing the host's awareness of being bitten and thereby extending the flies' feeding time. Biting flies feed during daylight hours only and tend to zero in on areas of thinner skin, such as the nape of the neck or ears and ankles.
Itching Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasan ...
and localized swelling and inflammation sometimes result from a bite. Swelling can be quite pronounced depending on the species and the individual's immune response, and irritation may persist for weeks. Intense feeding can cause "black fly fever", with headache, nausea, fever, swollen lymph nodes, and aching joints; these symptoms are probably a reaction to a compound from the flies' salivary glands. Less common severe allergic reactions may require hospitalization. Repellents provide some protection against biting flies. Products containing the active ingredient
ethyl butylacetylaminopropionate Ethyl butylacetylaminopropionate (trade name IR3535) is an insect repellent which is applied topically to prevent bites and stings from mosquitos, ticks, and other insects. It is a colorless and almost odorless oil, has efficacy against a broad ran ...
(IR3535),
DEET ''N'',''N''-Diethyl-''meta''-toluamide, also called DEET () or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection a ...
(''N'',''N''-diethyl-''meta''-toluamide), or
picaridin Icaridin, also known as picaridin, is an insect repellent which can be used directly on skin or clothing. It has broad efficacy against various arthropods such as mosquitos, ticks, gnats, flies and fleas, and is almost colorless and odorless. A s ...
are most effective. Some beauty products have been found effective, and their use as insect repellents have been approved by EPA (e.g., Skin So Soft). However, given the limited effectiveness of repellents, protecting oneself against biting flies requires taking additional measures, such as avoiding areas inhabited by the flies, avoiding peak biting times, and wearing heavy-duty, light-colored clothing, including long-sleeve shirts, long pants and hats. When black flies are numerous and unavoidable, netting that covers the head, like the “bee bonnets” used by beekeepers, can provide protection.


River blindness

Black flies are central to the transmission of the parasitic
nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...
''
Onchocerca volvulus ''Onchocerca volvulus'' is a filarial (arthropod-borne) nematode (roundworm) that causes onchocerciasis (river blindness), and is the second-leading cause of blindness due to infection worldwide after trachoma. It is one of the 20 neglected tr ...
'' which causes onchocerciasis, or "river blindness". It serves as the larval host for the nematode and acts as the vector by which the disease is spread. The parasite lives on human skin and is transmitted to the black fly during feeding.


See also

* "
The Black Fly Song "The Blackfly Song" is a song by Wade Hemsworth, written in 1949, about being tormented by black flies while working in the wilds of Northern Ontario. It is an enduring classic of Canadian folk music, covered by a variety of other artists. A new v ...
", a song by Wade Hemsworth inspired by his experiences with them in
Northern Ontario Northern Ontario is a primary geographic and quasi-administrative region of the Canadian province of Ontario, the other primary region being Southern Ontario. Most of the core geographic region is located on part of the Superior Geological Pro ...
and popularized in the United States by Bill Staines. * Gnat *
Midge A midge is any small fly, including species in several families of non- mosquito Nematoceran Diptera. Midges are found (seasonally or otherwise) on practically every land area outside permanently arid deserts and the frigid zones. Some mi ...
* Use of DNA in forensic entomology


Citations


General references


Black Flies Fact Sheet
from
Ohio State University The Ohio State University, commonly called Ohio State or OSU, is a public land-grant research university in Columbus, Ohio. A member of the University System of Ohio, it has been ranked by major institutional rankings among the best pub ...

Extensive Simuliidae (black fly) Web pages at blackfly.org.uk

Black fly species inventory


Further reading

* Crosskey R. W. ; ''The natural history of blackflies.'' Willey, New York, 1990. * Honomichl K. ; Bellmann, H. ; ''Biologie und Ökologie der Insekten.'' CD-Rom. Gustav Fischer, Stuttgart, 1994. * Jedlicka, L.; Stloukalova, V. ; ''Family Simuliidae.'' pp. 331–347 in: Papp, L. and Darvas, B. (eds.): ''Contributions to a Manual of Palaearctic Diptera'', Volume 2. Science Herald, Budapest, 1997. * Jensen, F. ; Diptera Simuliidae, Blackflies. pp. 209–241 in: Nilsson, A.N. (ed.): ''Aquatic Insects of North Europe. A Taxonomic Handbook''. Apollo Books, Stenstrup, 1997. * Kim, K. C. ; Merritt, R. W. (Eds.) ; ''Black flies, ecology, population management, and annotat. world list.'' University Park, London, 1987. * Kurtak, D. C. 1973. ''Observations on filter feeding by the larvae of black flies''. PhD thesis. Cornell Univ., Ithaca. 157 pp. * Kurtak, D. C. 1978. "Efficiency of filter feeding of black fly larvae". ''Can. J. ZooL'' 56:1608–23 110. * Laird, M. (Ed.) ; ''Blackflies.'' Academic Press, London, 1981. * Lechthaler, W. ; Car, M. ; ''Simuliidae − Key to Larvae and Pupae from Central− and Western Europe''. Vienna 2005, * Seitz, G. ; ''Verbreitung und Ökologie der Kriebelmücken (Diptera: Simuliidae) in Niederbayern.'' in: ''Lauterbornia.'' Mauch, Dinkelscherben 11.1992, pp. 1–230. * Timm, T. ; ''Dormanzformen bei Kriebelmücken unter besonderer Berücksichtigung des Ei-Stadiums (Diptera: Simuliidae).'' in: ''Entomologia generalis.'' Schweizerbart, Stuttgart 12.1987, 133-142. * Timm, T. ; ''Unterschiede in Habitatselektion und Eibiologie bei sympatrischen Kriebelmückenarten (Diptera, Simuliidae).'' in: ''Mitteilungen der Deutschen Gesellschaft für Allgemeine und Angewandte Entomologie.'' Bremen 6.1988, 156-158. * Timm, T. ; Rühm, W. (Hrsg.) ; ''Beiträge zur Taxonomie, Faunistik und Ökologie der Kriebelmücken in Mitteleuropa.'' Essener Ökologische Schriften. Bd.2. Westarp Wissenschaften, Magdeburg 1993. * Wichard, W. ; Arens, W. ; Eisenbeis, G. ; ''Atlas zur Biologie der Wasserinsekten.'' Stuttgart, 1994. * Wirtz, H. P. ; ''Analyse der Histaminanteile im Speichel verschiedener Kriebelmückenarten (Diptera: Simuliidae).'' in: ''Mitteilungen der Deutschen Gesellschaft für Allgemeine und Angewandte Entomologie.'' Bremen 6.1988, 441-442.


External links


Taxonomy and systematics of Simuliidae

Diptera.info Gallery
Images {{Authority control Insect vectors of human pathogens Upper Peninsula of Michigan Taxa named by Edward Newman