INSECTS>FFECTING MAN AND ANIMALS 197 



Various proprietary repellent solutions are in common use 

 for protecting cattle from flies. The principal objection to 

 them is that repeated applications are necessary to be ef- 

 fectual. If it is desired to use such sprays, a home-made 

 solution will be cheaper and equally effective. Use either 

 one part of pine tar with three parts of crude cottonseed oil 

 or fish oil, or three parts of crude carbolic acid to one hun- 

 dred parts of either of these oils. Cottonseed oil is less 

 offensive than fish oil, and cheaper. These may be applied 

 with a hand atomizer or sponge, but an atomizer or small 

 spray pump will use less material and apply it more evenly. 

 By having a man stand on either side of the door to spray 

 the cows as they enter the barn, dairy cows may be quickly 

 treated and the flies kept out of the barn. There seems to 

 be some question, however, as to the real efficacy of these 

 repellents, and whether they are ' really worth the cost. 

 Such experiments as have been carefully conducted are 

 rather inconclusive (24) on this point, but indicate that 

 whether the fly-sprays are profitable or not remains to be 

 determined. Undoubtedly they afford some relief for a 

 day or two. 



Preventive measures seem more promising. If the de- 

 velopment of the maggots in the cow manure can be pre- 

 vented, no flies will occur. In small pastures where the 

 manure is often dropped in particular places, it is entirely 

 feasible to send a boy around the field every few days and 

 let him spread out each dropping with a shovel, so that it 

 will dry out quickly in the sun. This is more necessary in 

 wet weather. At the barn, sprinkle lime or land plaster 

 over the manure every day or two, which will aid in pre- 

 venting the development of the maggots. Probably the 

 borax treatment advised for the house fly (page 178) will 

 be found even more effective. 



