FIELD BOOK OF INSECTS. 



the adult fly emerges after about thirty days" (Wash- 

 burn). A number of other species of this genus live in 

 the stomach of horses and asses. 



The Warble-flies of cattle, "whose larvae 

 Hypoderma are f ounc } f n small tumors under the skin, 

 also have their eggs swallowed, and the young larvae may 

 be found in the mouth and oesophagus. But from here 

 they burrow out into the body-tissues of the host, finally 

 coming to rest underneath the skin along the back. When 

 the larva or grub is full-grown it gnaws through the skin, 

 drops to the ground, pupates, and in from three to six 

 weeks changes to the adult fly. The hides of cattle 

 attacked by these flies are rendered nearly valueless 

 by the holes, and are known as 'grubby' hides. Osborn 

 estimates that these warble-flies, of which we have two 

 species, Hypoderma boms and H. lineata, cause a loss of 

 $50,000,000 annually in this country" (Kellogg). 



(Estrus ovis is the sheep-bot. Its larvae live in the 

 nasal and other head passages of sheep, causing th'e disease 

 known as staggers, grub-in-the-head, or false gid. The 

 larvae found in the throats of deer are those of Cephenomyia 

 abdominalis. Our largest species in the East, and prob- 

 ably our heaviest Dipteron, is Cuterebra buccata (Plate 

 LXVIII), whose larvae are found under the skin of rabbits. 



DEXIID.E 



"In habits and life histories, the Dexiidae closely re- 

 semble the Tachinidas, and the distinction between the 

 two families is very difficult to make, if it is not actually 

 evanescent" (Williston). 



TACHINID.E 



This is a family concerning which, from the human view- 

 point, nothing but good can be seen; but the taxonomy is 

 difficult and the difficulties are being greatly increased by 

 certain workers who found not only new species but even 

 genera on intangible differences. Amateur Lepidopterists 

 often raise Tachinids instead of Lepidoptera when they 



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