IMPORTANT FLIES 



113 



sanitary ways than by leaving them to the blowflies. Related 

 to these, and of importance in the southern states, is the screw- 

 worm fly (Chrysomyia maeellaria), which oviposits on wounds, 

 tlu* maggots feeding upon living flesh. These are the flies that 

 sometimes lay their eggs in nostrils or ears of children or of 

 people if asleep out of doors in the daytime, the maggots 

 causing painful and even fatal wounds. 



The stable fly (Stomoxys calcitrans), which has somewhat 

 the appearance of the house fly, except that it is provided with 

 a strong, piercing beak, sucks the blood 

 of animals. This fly is now convicted 

 of inoculating the germs of infantile 

 paralysis with its bite. It also causes 

 great suffering to cattle. The smaller 

 horn fly (Hoematobia serrata), imported 

 from Europe about 1886, is another 

 bloodthirsty pest of cattle, biting both 

 by night and day. It may be recognized 

 by its habit of clustering in masses 

 around the bases of the horns of cattle, 

 and may be trapped by the method 



FIG. 56. Stable flies that 

 a boy, with an insect net, 

 caught on a cow in one day 



recommended for the stable fly. 



The black flies, deer flies, sand flies, 



and the many botflies of horses, cattle, and sheep are all of 

 civic importance to the districts where they abound. The 

 black flies of the genus Simulium are now under suspicion 

 as possible carriers of pellagra. They breed in running water. 



Life history of the typhoid fly. In order to discover best 

 ways of attack, we must study natural enemies from every 

 point of view. The ease with which mosquitoes have been 

 exterminated has suggested similar methods for dealing with 

 flies. But mosquitoes breed only in stagnant water, which is 

 easily drained, filled, stocked with fishes, or oiled. Flies breed 

 in decaying filth, chiefly in horse manure, but can breed in any 



