11 - Black Flies (Simuliidae)

Abstract

Black flies are distributed worldwide, with the exception of Antarctica and some oceanic islands. Their distribution is largely influenced by the availability of flowing water, which is required for development during the immature stages. There are 1700 species of black flies worldwide. Two subfamilies comprise the Simuliidae. The morphological uniformity of black flies creates difficulty for species identification. The immature stages of black flies are adapted for aquatic life, although the nonmobile pupa also has terrestrial adaptations that are useful if the water recedes. The pupa, which resembles an adult with its appendages held close to the body, is housed in a silk cocoon. The adult black flies are characterized by a small but robust body, conical or beadlike antennae with seven to nine flagellomeres, and an arched thorax bearing a pair of wings that typically span 6–10 mm and have thickened veins near the leading margin. Larvae lead a largely sessile life. The distribution patterns of larvae and pupae are associated with a variety of environmental factors. The biting and nuisance problems inflicted by black flies have severe consequences for most outdoor activities, including agriculture, forestry, industrial development, military exercises, mining, and tourism. The veterinary impact of black flies is manifested through pathogen transmission, biting, and nuisance swarming. Filarial nematodes, protozoans, and possibly several viruses are transmitted to animals by black flies. These species are the vectors of the agents of human onchocerciasis and mansonellosis, bovine onchocerciasis, and avian leucocytozoonosis.