ANIMAL PARASITES OF CATTLE. 511 



pine tar containing from 10 to 50 per cent of the latter substance 

 were found by investigations in the Bureau of Animal Industry to 

 have a marked repellent action against flies when applied lightly 

 every day. A too free application of tar mixtures and other prepara- 

 tions containing phenols is liable to cause poisoning; hence care 

 should be observed in this regard. 



Jensen (1909) recommends the following formula, which is said 

 to protect cows for a week : 



Common laundry soap 1 pound. 



Water 4 gallons. 



Crude petroleum 1 gallon. 



Powdered naphtlialin 4 ounces. 



Cut the soap into thin shavings and dissolve in water by the aid of 

 heat ; dissolve the naphthalin in the crude oil, mix the two solutions, 

 put them into an old di^sher churn, and mix thoroughly for 15 

 minutes. The mixture should be applied once or twice a week with 

 a brush. It must be stirred well before being used. 



THE STABLE FLY (STOMOXTS CALCITRANS).' 



This fly very closely resembles the house fly, but, unlike fhe latter, 

 it is a biting fly. It is common about stables and often enters 

 dwellings, especially in cloudy weather. According to Noe, it is the 

 agent of transmission of a parasitic roundworm of cattle {Setarid 

 labiafo-papillosa, see p. 534). This fly has been shown capable 

 of transmitting anthrax from diseased to healthy animals, and under 

 some conditions it may transmit surra, a disease caused by a blood 

 parasite which affects horses, cattle, and other live stock. 



The annoyance sufi^ered by cattle and horses from stable flies is 

 much lessened if the stables are darkened. 



The screening of doors and windows, however, is preferable, as 

 ventilation is not interfered with as it is in darkening stables. For 

 milch cows coverings made from burlap (double thickness), includ- 

 ing trouserlike coverings for the legs, may be used when the flies are 

 very numerous and troublesome. One of the fly repellents men- 

 tioned above may be api^lied to cattle to protect them from stable 

 flies. The Hodge flytrap fitted to the windows of dairy barns is a 

 useful means of destroying stable flies. 



The stable fly breeds in moist accumulations of straw, chaff, cow 

 or horse manure, and various fermenting vegetable substances. The 

 debris collecting in and under outdoor feed troughs, and the remains 

 of straw stacks are favorable breeding places for the stable fly. 

 Under the most favorable conditions about three weeks are required 

 for development from the egg to the adult stage. 



1 For fiirtlipr information consult Farmers' Bulletin 540. 



