'Bo Mr, Curtis's Obfervations on Aphides, 



But what IS of greater confequence is, that it is enabled by their 

 ufe to cling faft to the bark of the tree as foon as it is brought forth, 

 and thus to obtain its necefTary nutriment. 



Of fome of the circumflances attendant on the propagation of 

 thefe minute animals accounts are related, deviating fo wonderfully 

 from the common courfe of nature, that they could not be credited, 

 were not the authors of them known to be men of the niceil and 

 mod accurate obfervation and of the flri6left veracity. On this part 

 of the fubje6l I have little to fay from my own obfervation ; but, as 

 fome account of fo extraordinary a part of their hiftory may be 

 expelled in a paper of this fort, I fhall flate the fads, briefly ob- 

 ferving that neither in the Aphis faltcis^ which at times I have 

 watched with great attention, nor in any other fpecies of Aphis ^ did 

 I ever obferve any fexual intercourfe to take place. Whether this 

 has arifen from the extreme infrequency of fuch a procedure, or 

 from my not having obferved thefe infects at a proper time of the 

 year, I know not; but, moft undoubtedly, fuch intercourfe does not 

 take place between the different fexes of Aphis as in other infcdls. 

 Yet Monf. Bonnet, who may be faid to have almoft taken up his 

 abode with thefe infe£ls, informs us that he has frequently noticed 

 fuch connexion, which he defcribes as taking place at one certain 

 time of the year only ; and that, from a female thus impregnated, 

 many fucceffive generations will be produced without any further 

 impregnation. He took the Aphides as foon as brought forth, and 

 kept each individual feparate. The females of fuch brought forth 

 abundance of young. He took the young of thefe and treated them 

 precifely in the fame manner. The produce was the fame ; and 

 thus he proceeded to the ninth generation with the fame fuccefs : 

 and fo far from confidering that as the utmoH: extent of the effcdl, 

 he thinks it might be carried on to the thirtieth generation. 



In 



