186 ZOOLOGY. 



grey. The maggots usually live in dung. Two 

 generations yearly : the first flies about in March ; the 

 second, and much more numerous one, in August and 

 September. Remedies : Cp. p. 165. 



Family: (Estridae (Bot Flies). 



Medium-sized or large flies (Fig. 121), with thick 

 hemispherical heads, and mouth-parts not strongly 

 developed. The antennae can be drawn back into 

 deep pits. The bot flies make a buzzing sound during 

 flight. The headless, twelve-ringed maggots live in 

 the bodies of various mammals. Their skin is provided 

 with numerous wart-like projections, or circlets of 

 spines. When very young the maggots are elongated 

 and cylindrical, and then possess a mouth-hook, which 

 disappears during the later moults. As soon as the 

 maggots are fully developed they leave the body of 

 the animal they inhabit, and let themselves fall to the 

 ground, where they become pupae within the shrivelled 

 larval skin. 



The following genera are distinguished: Warble 

 Flies (Hypoderma), and Bot Flies (CEstrus and Gastrus, 

 or Gastrophilus). To the first-named genus belongs 

 the 



Ox Warble-fly, or Ox Bot Fly {Hypodenna hovis), 



two-fifths of an inch long, black. Hair : whitish 

 yellow on the head ; reddish yellow on the fore part 

 of the thorax, black on the hinder part ; grey on the 

 fore part of the abdomen, black in the middle, and 

 reddish yellow behind. Legs black. Wings brownish, 

 not quite transparent. 



On the wing during summer (June to September). 

 As soon as the cattle hear the flies buzzing around 

 (especially on hot days) they become very restless, 

 run about as if mad, and even plunge down steep 

 places. Young cattle are selected for egg-laying ; 



