66 THE INSECT WORLD. 



The Gad-fly, or Breeze-fly of the sheep, (Estrus (Cephalemyia 

 ovis), has obtained notoriety on account of its attacking those animals. 



Even at the sight of this insect the sheep feels the greatest terror. 

 As soon as one of them appears, the flock becomes disturbed, the 

 sheep that is attacked shakes its head when it feels the fly on its 

 nostril, and at the same time strikes the ground violently with its 

 fore-feet ; it then commences to run here and there, holding its nose 

 near the ground, smelling the grass, and looking about anxiously to 

 see if it is still pursued. 



It is to avoid the attacks of the Cephalemyia that during the 



Fig. 49. Cephalemyia ovis. 



hot days of summer sheep lie down with their nostrils buried in 

 dusty ruts, or stand up with their heads lowered between their fore- 

 legs, and their noses nearly in contact with the ground. When these 

 poor beasts are in the open country, they are observed assembled 

 with their nostrils against each other and very near the ground, so 

 that those which occupy the outside are alone exposed (PLATE III.). 

 The Cephalemyia ovis (Fig. 49) has a less hairy head, but larger in 

 proportion to the size of its body than the Gad-fly (Gasterophilus cqut). 

 Its face is reddish; its forehead brown with purple bars; its eyes of 

 a dark and changing green; its antennas black, its thorax sometimes 



