INSECTS AFFECTING MAN AND ANIMALS 193 



furrow across the pasture so that the sheep may stick their 

 noses in the dust when they are attacked is recommended. 

 Inasmuch as the flies are abroad only in the sunshine and 

 in the heat of the day, any kind of cheap shelter which will 

 afford shade and into which the sheep may run will prove a 

 welcome refuge for them from the flies. Four posts with 

 any sort of a roof and bagging hanging loose down the sides 

 will be sufficient. When the maggots become established 

 in the head there is practically nothing which can be done 

 to remove them except an operation trephining which 

 must be done by a skillful veterinary surgeon and will only 

 be practicable for valuable breeding stock. 



119. The Ox Warble.* The ox warble (21), also known 

 as " bot-fly" or " heel-fly," is the cause of "grubby" hides 

 of cattle and in the grazing regions of the West and South- 

 west is the cause of considerable loss to both hides and beef. 

 Cattle allowed to run in pasture for the summer are always 

 more or less affected with the grubs, particularly if the owner 

 is not careful to destroy them. The holes in the hides, and 

 the loss in weight and quality, make the warble one of the 

 worst insect pests of cattle. 



The adult fly is about the same size and of much the same 

 appearance as the honey-bee. It is about a half inch long, 

 blackish, and clothed with hairs. The edge of the head and 

 thorax and the base of the abdomen are covered with whitish 

 hairs. The upper part of the head and thorax and the 

 middle of the abdomen and legs are blackish-brown. The 

 tip of the body is reddish-brown. The flies lay their eggs 

 on cattle, not infrequently on the flanks and elsewhere, but 

 mostly just above the hoof, which latter habit has given 

 them the name " heel-fly." The presence of one of the flies 

 causes intense excitement among the cattle, often stampeding 

 * Hypoderma lineata Villers. Family (Estridce, see page 139. 



