2 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE. 



chiefly in young sheep, sometimes in adult sheep when badly kept, 

 and the larvse hatching from the eggs become parasitic in the skin. 

 In Australia several species of blowflies (Calliphora oceanicw Desv., 

 0. villosa Desv., and G. rufifacies Desv.) produce a similar condition 

 in sheep. Recently a cutaneous invasion of sheep with dipterous 

 larvae occurring at Cobham, Va., was reported to this department, 

 but the fly responsible for the trouble has not been identified. The 

 application of repellents and parasiticides is indicated in case sheep 

 are subject to the attacks of such flies. 



The house fly (Musca domestica L.) commonly visits wounds on 

 animals to suck up the exudates that occur there. It is the cause of 

 considerable annoyance to animals in this way; it prevents wounds 

 from healing and may introduce into a wound agents of infection 

 adhering to its body. Repellents are therefore indicated and are 

 frequently used on wounds to keep house flies away and also to 

 keep away such flies as may deposit their eggs in wounds, such, for 

 example, as the screw-worm fly. 



The use of fly repellents is resorted to largely for the purpose of 

 relieving animals of the torment of biting flies or of preventing 

 infestation with the larvae of flies, without any reference to the con- 

 trol or eradication of such pests. In the case of such flies as the 

 stable fly and the hornfly, the use of repellents can be of only sec- 

 ondary importance as an eradicative measure, since a much more 

 effective means of getting rid of these pests lies in preventing them 

 from breeding. This may be done by preventing access of the flies 

 to materials such as manure, etc., in which they deposit their eggs, 

 and by destroying the young stages that may be present in such 

 materials. However, the eradication of these flies in most instances, 

 or even a reduction in their numbers in many cases, is out of the 

 question, so that it is necessary to resort to the use of repellents or 

 other means to give relief to animals. 



In the case of the horseflies, preventing them from biting is 

 probably as important a factor as can be taken advantage of in 

 bringing about control, yet it must be admitted that this means 

 can be of only very little importance. In the case of the bot flies 

 and the screw-worm flies, the use of repellents against the adults 

 and of parasiticides against the eggs and larva? is an important 

 method of eradication as well as a valuable means of protecting 

 animals. 



INJURY CAUSED DOMESTIC ANIMALS BY BITING FLIES. 



Aside from the transmission of various animal diseases by biting 

 flies, a matter of much less importance in this country than in the 

 Tropics, flies are generally assumed to be responsible for enormous 

 losses to farmers and stockmen. Because of the great numbers in 



