64 BRITISH APHIDES. 



understanding the various life-stages of a plant-louse 

 is to compare it with the growth of a plant. 



The egg, which is often single in the females of 

 Aphides, is not destiued, as in other insects, to pro- 

 duce a sexuated male or female ; it furnishes only an 

 a //anions form, which by a sort of budding process 

 (bourgeonement or gemmation in French, Keimung in 

 German) reproduces a great number of individuals able 

 to continue this budding reproduction for a more or 

 loss prolonged period, until there arrives a period in 

 which the produce of these gemmations consist no more 

 of agamic individuals all equal, but sexuated insects, 

 male and female, which last lays the fecundated egg, 

 and gives origin to a new series of beings. 



As I said before, this kind of evolution calls to 

 mind that of a vegetable, from the seed of which 

 arises the trunk, branches, leaves, and flowers by 

 gemmation, giving at last, once more, the fecundated 

 seed, through a kind of copulation. I suggested for the 

 agamous forms — thus able to reproduce by budding, 

 the name of Pseudogynae ; and, considering them to be 

 only transitory or larval forms, I gave the four life- 

 stages preceding the appearance of the sexuated 

 insects the following names : 



1. Pseudogyna fundatrix. 



2. — migrans. 



3. — gemmans. 



4. — 2 )U l J tf Gra ' 



I retained, of course, the names of male and female 

 for the sexuated forms, which show the genital organs 

 and are able to copulate. I called the first form 

 issuing from the fecundated egg the fundatrix (as a 

 translation of the German word Stammiitter), thus 

 indicating the first foundress of a colony. This is the 

 insect which generally forms the galls in those species 

 where galls are produced. Nevertheless, in some 

 species the power of forming gall-like swellings is not 



