THE BOT-FLIES 



(Family CEstridce.) 



This family contains the parasitic creatures known as bot- 

 flies, several of which are the cause of great suffering and even 

 the death of domestic animals. The bot-fly of the sheep (CEstrus 

 ovis), the bot-fly of the horse (Gastrophilus equi), the bot-fly of 

 the ox which is known in England as the" ox warble " fly (Hypo- 

 derma lineata, the European species being H. bovis), and certain 

 other forms whose larvae 

 live under the skin of such 

 wild animals as squirrels 

 and rabbits (genus Cuter e- 

 bra) and which are some- 

 times in tropical regions 

 found under the skin of 

 human beings ( Dermatobia 

 cyaniventris) belong to this 

 family. The group is not 

 a large one, comprising 

 only about sixty species and 

 the life history of the dif- 

 ferent species is quite variable, comprising many strange and 

 curious phenomena. All, however, are parasitic in vertebrate 

 animals. The flies themselves are rather large, generally rather 

 hairy, and they are as a rule inconspicuous in their coloration. 

 The antennae are small and inserted in rounded pits. 



Fig. 85. — CEstrus ovis. (After Riley.) 



Typical Life History 



(Hypo derma lineaia Villers.) 



This fly is the common ' ' ox bot "or" ox warble " of the United 

 States and is known in the southwestern country as the "heel 

 fly." To stock raisers its larva is also known as the "grub." 

 Affected cattle are known as " grubby " cattle. Early in the spring 



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