( 18Q ) 



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I have jnft defcrlbed, but alfo a great number of Flies, fo very mi-" 

 nute, that I fhould not have imagined they could exift in the open 

 air, for that the heat mufl caufe all the moill:ure in their bodies to 

 evaporate. 



The fight of thefc Flies caufed me to open all the webs which 

 had been left in the glafs, and in one of them I found a great 

 number of minute Ikins or cafes, from which thofe Flies had pro- 

 ceded by tranfmutation from aurelias. From whence I concluded, 

 that a minute Fly of this fpecies, muft have laid many eggs in the 

 aperture of one of thefe v/cbs, and the Maggots hatched from thence, 

 muft have fed upon the caterpillars in the web, until they came to 

 their full growth, and then within the web be changed into thofe 

 mmute Flies ; otherwife, in my opinion, that fpecies of Fly would 

 become extinct. For we mull lay it down as a truth, that many 

 flying animals live on nothing but other living creatures, and for 

 want of which food many of them die, efpecially the fmall ones, 

 among which may properly be reckoned Flies : for if many Flies 

 could not find particles of fleili whereon to lay their eggs, the mag- 

 gots bred from thofe eggs mull perifii. 



This innate difpofition and forefight in fmall animals leading then? 

 to lay their eggs in thofe places where the young maggots may find 

 food and nourifhment, will appear ftrange to many. But if we 

 confider the nature of larger fiying animals which are familiar to 

 us, and that we never fee geefe, ducks^ or fwans, make their nefis 

 in trees, or in fields far difi:ant from the water, but always on the 

 banks of ditches or rivers, becaufe they do not bring food to their 

 young, who are by nature defi:ined to feek it for themfelves ; and 

 therefore the parents, when the young are hatched, do no more 

 than tend on them and proteft them from enemies ; whereas, on the 

 contrary, we fee that birds who arc able to bring food to their 

 young, build their ncfis on the tops of trees and other high places, 

 and that the young remain in the nefis, and do not endeavour to 

 follow their parents, however lumgry they may be, we ll;all ceafe 



