^^6 TriE Tvr, 



When the dllFerent members have acquired fufficient 

 firmnefs, the fly is ready to burfc from its Ihell in its 

 \vinged form. The covering of the chryfalis, efpecially 

 of thofe \yho are metamorphofed in their own Ikin, feem 

 to prove, by their hardnefs, an efFeclual bar to that events 

 About the time, however, of its change, the head of the 

 fly is capable of being fwcllen and dilated in an unufual 

 manner ; and it is by means of this dilatation that the 

 fly burfls its covering, and opens a palTage for its 

 efcape. 



The food of flies is as various as their diiT^rent kinds ; 

 feme being fupported Vv'holly by vegetable fubilances, 

 while others are carnivorous ; and among the latter there 

 are fome who only devour flefli in a ftate of putrefadion. 

 Dung, and vegetables In a fimilar ftate, are the favourite 

 meals of others. In the hiflory of the aeftrus, we liav^e 

 already noticed that inilln£l by which the females are di- 

 rected to depoiit their eggs within reach of food proper 

 for each fpecies f . 



The female flies are all fecundated by copulation ; an 

 aft in which the moft incurious obferver muil have fre- 

 quently feen them engaged. The obfervations of ReaU" 

 7nur feem to prove, that the females of fome kinds take 

 that part in the act of fecundation which is ufually per- 

 formed by the male in other animals ; and that it is her 

 extremity which penetrates into the body of the male. 

 The far greater part of infers are oviparous ; fome, how- 

 ever, belonging to this genus bring forth living young : 

 But what appears mofl; unaccountable is, that fome appa- 

 rently of the fame fpecies are viviparous, while the reft 



lay 



f Page 97, 



