192 



SCHOOL ENTOMOLOGY 



and the abdomen is velvety dark brown variegated with straw 

 color. The fly has no mouth-parts and so takes no food. 

 The female lays the young maggots (the eggs having been 

 hatched in the body of the parent), in the nostrils of the 

 sheep. The attacks of the flies make the sheep frantic and 

 they will lie down and bury their noses in the dust, throw 

 dust in the air, and huddle together to try and ward off the 

 attack. The young larva works its way upward into the 

 frontal sinuses, the cavities between the plates of bone over 



the eyes. It requires 

 about ten months for 

 the larva to become 

 mature, when it crawls 

 back into the nose 

 and is sneezed out. 

 Going an inch or two 

 below the surface of 

 the soil it transforms 

 to the pupa, from 

 which the adult fly 

 emerges in from four 

 to six weeks. When 

 the grubs become 

 numerous in the frontal sinuses they often cause very serious 

 injury, animals so affected losing their appetite, becoming 

 emaciated, discharging thick mucus from the nose, etc. 



No entirely satisfactory method of control is known. 

 The best means is to smear coal-tar on the sheep's noses. If 

 one has but a few sheep this can be done now and then by 

 hand. Otherwise, place logs in which holes are bored with 

 a two-inch augur here and there in the pasture. Keep these 

 holes about half full of salt and the edges smeared with coal- 

 tar, so that it will get on the sheep's noses. Plowing a deep 



FIG. 136. Sheep bot-fly ((Estrus ovis). 

 (After Riley.) 



1, 2, flies; 3, pupa; 4, full-grown larva. 



