BLACK FLY. A gnat of the forest regions of north temperate latitudes, especially torment ing to man and beast, and representing the fain ily Simuliid:e. All the insects of this family are short. small, and thick-bodied, having no simple eyes and no transverse suture in the thorax; they rarely exceed one-fourth inch in length. The larva. of these flies are aquatic, unlike mosqui toes, living in swift-running streams. Their eggs are deposited in closely packed layers on rocks near or below the surface of the water, into which the larvw drop when freed from the egg and become attached to plants, stones, etc., by a silken thread, or sometimes to each other, form ing long floating strings; they soon pupate within silken cocoons, open at the ends so as to admit water. There may be several broods, the last producing young that hibernate ill the larval stage. Bence the first emergence of imagoes (flies) is early in the spring. As summer advancesthein sects become excessively in such fa vorable regions for them as the well-watered for ests of northern New York, Maine, and Canada, where in hot weather they abound ill such swarms as to put a stop to work in the woods, and even to cause the death of poultry and other animals which cannot escape them. in Labrador, life
is practically impossible away from the seashore while the flies are in force. They suck the blood like mosquitoes, but, unlike them, are worse in sunshine, becoming dormant on cloudy days. Three or more species are known, that of the Saint Lawrence Valley (Shan/him inrcanstunt) being different from that of Lake Superior. To protect themselves. people build smudges and smear their faces and hands with ointments, of which the best is oil of tar, habitually used by the employ(•s of the Hudson Bay Company. Consult, for a monograph of the group, Bulletin :Vo. 10. Ent. Division, U. S. Dept. Agric. (Wash ington, IS9S). See BUFFALO-GNAT.