Black Fly (Buffalo Gnat)

Family Simuliidae — the black flies, also called buffalo gnats — contains about 2,200 species worldwide. All Simuliidae are blood-feeding as adults (females only; males drink nectar) and aquatic larvae (filter-feeding in fast clean running water — black flies are an indicator of high stream water quality, as the larvae cannot survive in polluted or slow water). Bites are intensely irritating: black fly mouthparts use scissor-mandibles to slice the skin (similar to horse flies but smaller scale), and bites often produce blood spots, swelling, and persistent itching. In livestock, mass black fly attacks can cause anemia and (in extreme cases) death from hypovolemic shock or anaphylactoid reaction to mass envenomation. The Simulium damnosum complex (about 10 sibling species) in West and Central Africa is the vector of Onchocerca volvulus — the parasitic nematode that causes onchocerciasis (river blindness). Female black flies acquire microfilariae from infected humans during a blood meal, the worms develop into infective larvae over 6-12 days, and the larvae are injected into the next human bitten. Adult worms live in subcutaneous nodules and produce millions of microfilariae over a 10-15 year lifespan; the microfilariae migrate through the eyes and skin, causing dermatitis, severe itching, and progressive blindness. The Onchocerciasis Control Programme (1974-2002), launched by WHO and the World Bank, dramatically reduced river blindness across 11 West African countries through aerial larviciding of breeding rivers — one of the most successful single-disease public-health programs ever conducted.