REPKODUCTION OF APHIDES. 115 



the sow, has been said to undergo something like a 

 segmentation. But as one swallow does not make a 

 summer, so great caution must be exercised before 

 any idea of parthenogenesis can be extended to these 

 higher animals, based upon observations so few in 

 number. 



Space does not permit here to enter on the vexed 

 question as to the difference between animal buds and 

 true and fictitious ova. The subject has been already- 

 treated by Yon Siebold, Leydig, Leuckart, Huxley, 

 Claperede, and others. Indeed, it would seem to 

 be difficult to come to a unanimous opinion, whilst 

 sexuality is allowed by some to have little or no weight 

 in the argument. Brandt remarks as to partheno- 

 genesis, ' f It is partly to be met with as a normal 

 condition, and partly as an exceptional condition ; 

 as we find to be the case with so many insects. How- 

 ever interesting the fact of the want of a seminal re- 

 ceptacle in the oviparous Aphis may be, from a physio- 

 logical or a morphological point of view, one can 

 nevertheless hardly attribute to it a fundamental signi- 

 ficance, but rather view it as of secondary, adapta- 

 tional import."* This would seem to imply that there 

 is but little real difference between an impregnated 

 and unimpregnated egg (?). 



Amongst Insects a modified parthenogenesis has 

 been observed in Sphinx pojpuli, S. ocellata, Arctia 

 caja, and several other genera of Lepidoptera. Mr. 

 Davis raised three parthenogenetic generations from 

 the eggs of the egger moth, Lassiocampa quercus. The 

 marked rareness of the male in Cynips is well known; 

 and the same scarcity may also be noticed in Coccus. 

 Doubtless, however, in some cases males are overlooked 

 on account of their diminutive proportions. 



Von Siebold some years ago noted the remarkable 

 fact that reproduction occasionally takes place in the 

 larval phases of some insects. He gave the term 

 Thelytolcy to the process usually known as partheno- 



* Dr. A. Brandt, ' Ueber das Ei und seine Bildungsstatte,' p. 55* 



