INSECTICIDES FOR ANIMALS 437 



make a clear, dark brown fluid. The resulting solution of cresol 

 soap is then ready to use. This cresol soap will mix in any pro- 

 portion with water and yield a clear solution. Use a 20 per cent 

 solution for disinfecting chicken houses, incubators, etc. 



The kinds of parasites. 



Following are the leading external parasites of cattle, horses, sheep 

 and swine (for parasites of poultry, see page 377). 



Cattle. Ox BOT-FLY OR WARBLE-FLY (Hypoderma bovis and H. 

 lineata). Large lumps or warbles along the animal's back filled with 

 pus, within which a large, thick-bodied maggot develops. When full 

 grown these maggots, about an inch in length, work their way out 

 through the skin, fall to the earth, and there after a time transform to 

 a large blackish fly with yellow markings. The flies glue their eggs 

 to the hair of the host, usually around the heels and flanks. The 

 eggs are licked off by the animal, hatch in the mouth or oesophagus, 

 and the larva bores its way through the tissues until it comes to lie 

 under the skin along the back. The cattle have an instinctive dread 

 of the flies, and are thrown into a panic by their presence. Badly 

 infested animals lose flesh, and the flow of milk is greatly reduced ; 

 the holes made in the skin also decrease the value of the hide. 



Treatment. Squeeze out and crush the grubs and disinfect the 

 sore. The practice of killing the grub under the skin by the application 

 of grease or kerosene is more liable to cause an infection from the de- 

 caying maggot and produce a serious sore. 



HORN-FLY (Hcematobia serrata). Flies considerably smaller than 

 the house-fly, which they closely resemble in shape and color. They at- 

 tack cattle in great numbers, clustering on any part of the body and 

 sucking blood. They have the peculiar habit of resting in dense 

 clusters on the horns. The eggs are laid and the maggots develop in 

 fresh droppings, and the transformation to the fly takes place in the 

 ground. 



Treatment. Spread out or mix with lime the manure as soon as de- 

 posited, to prevent the development of the maggots. Let hogs run 

 with the cattle ; scatter the manure. Spray the animals with crude 

 oil emulsion often enough to prevent attack, or apply train oil or 

 a mixture of two parts of crude cottonseed oil and one pint of pine 

 tar. The last two may be applied with a large brush, and remain 



