332 The Diseases of Animals 



the thorax. The adult fly deposits its eggs on the sur- 

 face of a wound. They hatch within a few hours, the 

 larvae (maggots) burrowing their way into the tissues, 

 where they remain for about a week. Then they escape 

 to the ground, pupate, and soon change into adult flies. 



In some regions the screw -worms are a great pest, 

 and cause serious loss to live stock. They attack an 

 animal in even the smallest wound, such as the punc- 

 tures made by ticks, wire cuts, brands, and the like. 



The treatment recommended by Dr. Francis, of 

 Texas, is to use pure creolin, or similar coal-tar prod- 

 uct, in a machinist's oil-can, squirting it thoroughly into 

 the wound. Oil of tar is also good. Fresh wounds can 

 be protected by covering with tar. 



THE HORN -FLY 



The horn -fly is a small insect (Hcematobia serrata) 

 about half the size of the common house -fty, and of the 

 same general shape. It was imported into America about 

 1887, and has spread over the whole country. It is a 

 European insect. It causes considerable irritation to 

 cattle, and a consequent loss of milk and flesh. The 

 name comes from the fact that these flies collect in 

 large numbers at the base of the horn to rest. They 

 do not bother cattle when in this position, but bite 

 them on the skin of the back, sides and flank. 



Apply some substance to the surface of the animal's 

 body to keep the flies away. A mixture of equal parts 

 of pine-tar, kerosene and fish -oil is excellent. The tar 

 is first "cut" by the kerosene, then the fish -oil is added. 



