IMPORTANT FLIKS 



113 



sanitary ways than by leaving them to the blowflies. Related 

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

 \vorm fly (Ckrysomyia macellaria), which oviposits on wounds, 

 the 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 

 < i using painful and even fatal wounds. 



The stable fly (StomoxyB ealcitransi), 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 (Hcematolna serrate), 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. 66 Stable flies that 



J J a boy, with an insect net, 



recommended for the stable fly. caught on a cow in one day 



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 

 \A ays 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 

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



