mosquito (məskēˈtō) [key], small, long-legged insect of the order Diptera, the true flies. The females of most species have piercing and sucking mouth parts and apparently they must feed at least once upon mammalian blood before their eggs can develop properly. The males may have beaks, or probosces, but cannot pierce, and they feed upon fruit and plant juices. The female produces the characteristic whining sound by vibrating thin horny membranes on the thorax. Mosquitoes have become adapted to extremes of climate and are found far north of the Arctic Circle, where they winter as larvae frozen in the ice.
Mosquito eggs are laid singly or glued together to form rafts, usually in stagnant water in ponds, pools, open containers, and other aquatic habitats—the particular type of habitat depending on the species. The aquatic larvae, or wrigglers, pass through four larval stages, feeding on microscopic animal and plant life. Except in the genus Anopheles, the wriggler has an air tube near the end of the abdomen and makes frequent trips to the surface to use it as a supplement to the gills. The pupa, or tumbler, shaped like a question mark, takes no food but surfaces often to breathe through air tubes on its thorax. One method of mosquito control is the spreading of oily substances on infested water, which prevents access to air and suffocates the pupae. In summer the life cycle may take only two weeks, resulting in several generations a year in some species.
During blood meals the females may either acquire or transmit various disease organisms. Several species of Anopheles mosquitoes, recognizable by their tilted resting position, carry the protozoan parasites that cause malaria; species of the genus Aedes transmit the viruses responsible for yellow fever, jungle yellow fever, and dengue fever; and in the S United States and in the tropics, members of the genus Culex, to which the common house mosquito belongs, are vectors of filariasis, the infection by a filarial worm that causes elephantiasis, and human encephalitis.
Dragonflies, damselflies, and several insectivorous birds are the natural enemies of the adults; the wrigglers are eaten in large quantities by small fishes and aquatic insects. Control of these major insect pests by other than natural means poses many problems; the long-range harmful effects of many insecticides are very serious, and swamp drainage tends to upset the balance of nature in addition to eliminating the mosquito.
Mosquitoes are classified in the phylum Arthropoda, class Insecta, order Diptera, family Culicidae.
See bulletins of the U.S. Dept. of Agriculture; study by A. Spielman and M. D'Antonio (2001).