Sand fly is a hairy, dark-brown insect that measures about 1/8 inch (3.2 millimeters) long. Female sand flies are active at night, and suck blood from human beings and animals. The larvae (young sand flies) live in moist places and feed on decaying plant and animal matter.
About six kinds of true sand flies live in the southern United States. But several hundred kinds thrive in the tropics and subtropics. They transmit germs that cause such serious diseases as kala-azar and sand fly fever.
Moth flies are related to sand flies, but they do not suck blood. Their wings fold over the body like a roof. Biting midges are sometimes called sand flies. In spring and fall, biting midges may appear in swarms. They rank among the smallest blood-sucking insects. Some are only 1/25 inch (1 millimeter) long.
