66 



THE INSECT WORLD. 



Tiff. 47. Imago of 

 Bot-fly emergirg. 



piece, which the fly gets rid of when it is in a fit state to come 

 into the open air." 



Fig. 47, taken from drawings in Reaumur's 

 memoirs, represents the imago of the CEstrus leav- 

 ing the cocoon. 



The reader is, most likely, desirous to know 

 with the aid of what instrument the CEstrus is 

 able to pierce the thick skin of the ox. 



The female only is possessed of this instru- 

 ment, which is situated in the posterior ex- 

 tremity of the body. It is of a shiny blackish 

 brown colour, and as it were covered with scales. 

 By pressing the abdomen of the fly between 

 one's two fingers it is thrust out. Reaumur 

 observed that it was formed of four tubes, which 

 could be drawn the one into the other, like the tubes of a telescope 

 (Fig. 48) . The last of these appears to terminate in five small 

 scaly knobs, which are not placed on the same line, 

 but are the ends of five different parts. Three of 

 these knobs are furnished with points, which form an 

 instrument well fitted to operate upon a hard thick 

 skin. United together, they form a cavity similar 

 to that of an auger, and terminating in the form 

 of a spoon. 



The gad-fly or breeze-fly of the sheep (Cephalcemia 

 (CEstrus) ovis) has obtained notoriety on account of its 

 attacking those animals. 



Even at the sight of this insect the sheep feels the 

 rea * es ^ 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 Cephal&mia that during the 

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

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



