ANIMAL PARASITES OF CATTLE 503 



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 naphthalin 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 dasher 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 (STOMOXYS CAX,CITRANS).i 



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

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

 dwellings, especially in cloudy weather. According to No6, it is the 

 agent of transmission of a parasitic roundworm of cattle (Setaria 

 lahiato-papillosa, see p. 529). 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 livestock. 



The annoyance suffered 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 

 milk cows coverings made from burlap (double thickness) , including 

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

 numerous and troublesome. One of the fly repellents mentioned 

 above may be applied 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 United States Bureau of En- 

 tomology has found that a mixture of fish oil (1 gallon), oil of pine 

 tar (2 ounces) , oil of pennyroyal (2 ounces) , and kerosene (| pint) is 

 fairly effective for a short time when applied lightly, but thoroughly, 

 to the portions of animals not covered with blankets. The risk of 

 poisoning with tar mixtures as already mentioned should be borne in 

 mind in using this remedy. Care should be taken to apply it lightly. 



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

 or horse manure, and various fermenting vegetable substances. The 



1 For further information consult Farmers' Bulletin 1097. 



