Microscopical Essays. 255 



each fupply two more, which caff, off their coverings three or four 

 times, according to the different warmth of the feafon. This fre- 

 quent change of their outward coat is the more extraordinary, 

 becaufe it is repeated more often when the infecls come the 

 fooneft to their growth, which fometimes happens in ten days, 

 where warmth and plenty of nourifhment conipired. 



Early in the month of June, fome of the third generation which 

 were produced about the middle of May, after carting off their 

 laft covering, difcover four erecl; wings, much longer than their 

 bodies ; and the fame is obfervable in all the fucc eding genera- 

 tions which are produced during the fummer months, but ftill 

 without any diverfity of fex ; for fome time before the aphides 

 come to their full growth, it is eafy to diftmguifh which will have 

 wings, by a remarkable fullnefs of the breaft, which in the others 

 is hardly to be diftinguiihed from tie body. When the laft 

 covering is rejected, the wings, which were before folded up in a 

 very narrow compafs, are gradually extended in a very furprizing 

 manner, till their dimenfions are at laft very confiderable. 



The increafe of thefe infecls in the fummer time is fo very 

 great, that by wounding and exhaufting the tender moots they 

 would frequently fupprefs all vegetation, had they not many 

 enemies to reffrain them. Notwithfianding thefe in feels have a 

 numerous tribe of enemies, they are not without friends, if thofe 

 may be confidered as fuch, who are officious in their attendance 

 for the 1 good things they expect to reap thereby. The ant and 

 the bee are of this kind, collecting the honey in which the aphides 

 abound, but with this difference, that the ants are conflant 

 vifitors, the bee only when flowers are fcarce 5 the ants will fuck 



in 



