| Black fly | |
|---|---|
 | |
| Simulium trifasciatum | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Superfamily: | Chironomoidea |
| Family: | Simuliidae Newman, 1834 |
| Subfamilies | |
Genera
| |
Black flies orblackflies[2] (sometimes calledbuffalognats,turkey gnats, orwhite socks) areflies in the familySimuliidae of theCulicomorphainfraorder. Simuliidae are related to theCeratopogonidae,Chironomidae, andThaumaleidae. Over 2,200 species of black flies have been formally named, of which 15 are extinct.[3] They are divided into two subfamilies:Parasimuliinae contains only one genus and four species;Simuliinae contains all the rest. Over 1,800 of the species belong to the genusSimulium.[3]
Black flies are usually small, black or gray, with shortlegs andantennae. They feed mainly onnectar for flight energy, and the females of most species also gain nourishment for egg production byfeeding on the blood of birds or mammals, including humans. They are a common nuisance for humans, and many U.S. states have programs to suppress the black fly population. They spread several diseases, includingriver blindness in Africa (Simulium damnosum andS. neavei) and the Americas (S. callidum andS. metallicum in Central America,S. ochraceum in Central and South America).
Eggs are laid in running water, and thelarvae attach themselves to submerged rocks. Breeding success is highly sensitive to water pollution.[4] 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, also termed "mouth brushes".[5] 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 onlotic (flowing water) 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 bephoretic on mayfly nymphs.[citation needed]
Adult males and females feed on water and a source of carbohydrate, such as nectar orhoneydew, for energy for flight.[6] Females of most species also exhibitanautogeny and bite birds or mammals to feed on blood for nutrients to produce eggs;[7] the mouths of males are not able to bite through skin.[6] Different species prefer different hosts 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. Some species in Africa can range as far as 40 mi (64 km) from aquatic breeding sites in search of their blood meals, while other species have more limited ranges.[citation needed] In the small percentage of species that do not bite, the females produce eggs using nutrients they have retained from the larval stage.[6] Male black flies are rarely seen.[7]
Black flies may be eitherunivoltine ormultivoltine, 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.[citation needed]
Work conducted atPortsmouth University in 1986–1987[citation needed] indicatesSimulium 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.[citation needed]
Only four genera in the family Simuliidae,Simulium,Prosimulium,Austrosimulium, andCnephia, contain species that feed on people, though other species prefer to feed on othermammals or onbirds.Simulium, the type genus, is the most widespread and is a vector for several diseases, includingriver 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.[12] 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 themaxillae andmandibles, cutting the skin and rupturing its fine capillaries. Feeding is facilitated by a powerfulanticoagulant in the flies'saliva, 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 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.[13][14]
Repellents provide some protection against biting flies. Products containing the active ingredientethyl butylacetylaminopropionate (IR3535),DEET (N,N-diethyl-meta-toluamide), orpicaridin 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).[15] 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.[16]
Black flies are central to the transmission of theparasiticnematodeOnchocerca volvulus which causesonchocerciasis, or "river blindness", which is endemic in parts ofSouth America,Africa, and theArabian Peninsula. It serves as thelarval host for the nematode and acts as thevector by which the disease is spread. The parasite lives on human skin and is transmitted to the black fly during feeding.[14]
{{cite journal}}: CS1 maint: bibcode (link)| National | |
|---|---|
| Other | |
