28 PARASITOLOGY. 



Histojy. — Found in common with the Gastrophilus 

 Equi in North America and Europe. 



Description. — Not so largfe as the Gastrophilus 

 Equi. The thorax is covered with olive-gray hair ; 

 a black band is found in the middle. The abdomen 

 is white in front, black in its median part, and orange 

 red at the posterior end. 



Life Cycle. — The eggs are oval in shape and black 

 in color. The larvae are taken into the mouth and 

 swallowed, and then, by means of two booklets, at- 

 tach themselves to the mucous membrane of the 

 digestive tract. They are found mostly in the right 

 and left sacks of the stomach. They may loosen 

 their hold and become attached at another point. 

 They often become attached to the rectum, causing 

 itching, and rubbing of the tail. The pupal stage 

 lasts from four to six weeks, and is passed in the 

 ground. 



Animal Attacked. — The horse. 



Parts Infested. — Stomach and intestines. 



Oestrus Ovis (Oestrus — gad-fly; ovis — sheep). 



Syno7iyms. — Cephalemyia ovis (cephalo — head, 

 myia — fly); sheep-bot; grub; ^^ 



head-maggot ; sheep gad-fly. ^^^ .<i^^b^ 3 



History. — Found in Ameri- ^S2 ^^^ ^ 



ca, Europe, Asia, Africa and S5/ 



Australia. ^Sr 



Description. — Small, yel- ^. , ^ ^^ t 



^ ' •' Fig. 5— Oestrus Ovis Larva, 



lowish gray fly, slightly larger a, side View, 

 than the house-fly. Body b, Posierior view. 

 covered with short flne hair. The abdomen is orna- 

 mented with five rings ; under side of head is white. 



