OF NATURAL HISTORY. 223 



When caterpillars, fome time before their change, are deprived of 

 food, they diminifh to at leaft one half of their former fize. Their 

 chryfalids, of courfe, as well as the butterflies which proceed from 

 them, are proportionally fmall. From this fadl we learn the impor- 

 tance of feeding all young animals well till they acquire their full 

 growth. 



It is aTemark of the ingenious Reaumur, that fuch infeds as feed 

 upon dead carcafles, and whofe fecundity is great, never attack live 

 animals. The flefh-fly depofits her eggs in the bodies of dead ani- 

 mals, where her progeny receive that nourifliment which is beft fuit- 

 ed to their conftitution. But this fly never attempts to lay her eggs 

 in the flefh of found and living animals. If Nature had determined 

 her to obferve the oppofite conduct, men, quadrupeds, and birds, 

 would have been dreadfully afflicted by the ravages of this fingle 

 infedl. Left it might be imagined that the flefh-fly feleded dead, 

 inftead of live animals, becaufe, in depofuing her eggs, fhe was un- 

 able to pierce the fkin of the latter, M. de Reaumur made the fol- 

 lowing experiment, which removed every doubt that might arife on 

 the fubjedl:. He carefully pulled of all the feathers from the thigh of 

 a young pigeon, and applied to it a thin flice of beef, in which there 

 were hundreds of maggots. The portion of beef was not fufliicient 

 to maintain them above a few hours. He fixed it to the thigh by a 

 bit of gauze ; and he prevented the pigeon from moving, by tying 

 its wings and leggs. The maggots foon fliewed that their prefent 

 fituation was difagreeable to them. Moft of them retired from under 

 the flice of beef; and the few that remained periftied in a ftiort time. 

 Their death was probably occafioned by the degree of heat in the 

 pigeon's body being greater than their conftitution could bear. Up- 

 on the fame pigeon M. de Reaumur performed another experiment. 

 He took off the fkin from its thigh, laid bare the flefh, and applied 

 immediately another flice of beef full of maggots. The animals 



difcovered. 



