534 THE FLT. 



anf^ are extremely deftrudlve to butcher meat, and otli«r 

 Jcinds of provifion. 



Next to the number of flies, their variety claims our 

 attention. The diiferent fpecies are extremely diverfified 

 in their external form, their flrudlure, their organization, 

 their metamorphofis, their manner of propagating their 

 fpecies, and in providing for their pofterity. A full ex- 

 planation of thefe different parts of their economy, would 

 requii'e a large volume, and would conftitute a narrative 

 to many readers not unintert fling. Such an undertaking, 

 however, is inconypatible with the limits prefcribed to 

 pur work. 



Some of thefe infe£ts have trunks inftead of a mouth ; 

 others have that organ armed with teeth ; and many have 

 both a mouth and a trunk. The probofcis of flies is a 

 machine contrived for pumping the blood from the vef- 

 fels of large animals, and the neftar from the petula of 

 flowers ; and the fcience of hydraulics has not enabled 

 men to conftrucl machines more complicated, more ex- 

 a£Hy arranged, or better adapted to thefe purpofes. Some 

 of them pofiefs confiderable firmnefs and folidity, thofe 

 efpccially that are deftined to pierce the Ikius of cattle. 

 In order to fte tliem at viork, all that is necefl'ary is to 

 expofe a fyrup to attract thena, and to take up a lens for 

 their infpeftion. 



Each eye of the fly contains in it an alTemblage of a 

 great number of fmall ones, which probably have the 

 cffeft of multiplying the furrounding objeds, and creating 

 reprefentations of them, which the experience of the in- 

 fect corrccis *. From the eye, if you pafs along and fur- 



vej 



* Reaumur, Toaic IV. Mem. v^. 



