INSECTA 109 



larvae are aquatic and some are known as " blood- worms" 

 on account of their color. Fishes commonly feed on them 

 and on midge pupae. Many birds, insects, and spiders 

 eat the adult midges, which often occur in great swarms, 

 covering trees, buildings, and everything else over large 

 areas. Such swarms are more apt to come in the spring 

 than at other seasons of the year. Though some of the 

 midges resemble mosquitoes in general appearance, most 

 species are perfectly harmless. The larvae live mostly on 

 aquatic vegetation and the adults usually do not suck 

 blood. The minute "punkie" or "no-see-um," of the 

 northern woods is an exception, as those who have been 

 punctured by these minute pests can testify. 



The gall-gnats (Cecidomyiidce) resemble mosquitoes in 

 appearance but do not bite. Their larvae differ consider- 

 ably in their habits, but those of most species form galls 

 on the twigs or leaves of plants. The most notable species 

 of the family is the Hessian fly, Cecidomyia destructor; 

 which does many millions of dollars worth of damage annu- 

 ally to the wheat crop of the United States. Another com- 

 mon species forms curious galls on willows, which resemble 

 pine cones in shape (Fig. 52). Others live on the golden 

 rod, sunflower, aster, and other plants. The little black- 

 flies, sand flies, or buffalo-gnats (Simuliidce) are stout, 

 hump-backed Diptera which are great pests in many parts 

 of the world. Their larvae live in swift flowing streams. 

 The adults are extremely blood-thirsty; cases are known 

 in which cattle, and once even a man, were killed by the 

 bites of these little insects. 



Among the short-horned flies (Brachycera, Fig. 53) 

 the horse-flies (Tabanidce) may first be considered. These 

 insects are also known as gad-flies, deer-flies, breeze-flies, 

 etc. They are active, strong-flying creatures. The females 

 live by sucking blood from warm-blooded animals, but the 

 males are harmless and get their sustenance from plant 

 juices. Tabanids usually lay their eggs above water on 

 cat-tails, rushes, and other aquatic plants. The larvae- are 



