PHYLLOXEUIDiE, 65 



limited to the Pseudogyna fundatrixy e.g. Phylloxera 

 vastatrix. 



The name of Pseudogyna migrans was suggested by 

 the fact that in the greatest part of plant-lice the 

 second form is winged and flies away from the place 

 where it was born. Yet here, as in the preceding 

 case, there may be exceptions, and some kinds do not 

 leave their birthplaces. Still, I regard emigration as 

 the rule. 



I gave the name of gemmans to the form succeeding 

 the emigrant, because it is the curious period in which 

 the budding reproduction gets to such a height, that 

 Bonnet was able to obtain without access of the male 

 nineteen generations from Aphis sambuci. Kyber, of 

 Eisenach, and later Schrader, of Bordeaux, noted 

 four years' reproduction from Siphonophora rosaz and 

 Phylloxera vastatrix. As to this last one, I am my- 

 self well convinced that the power of reproduc- 

 tion of the underground Pseudogyna gemmans of 

 the root form, has occurred in a piece of vineyard 

 of my own property ever since 1875, and the pro- 

 cess is probably everlasting. Of course this will 

 happen only as long as food and temperature allow 

 it, because the two conditions of heat and nourish- 

 ment have the greatest influence on the repro- 

 ductive power of the agamous-gemmans form in all 

 Aphides. Here also, as in the two preceding states, 

 numerous exceptions to the rule find place ; for if it is 

 possible and even easy, by maintaining Aphides on 

 fresh leaves or fresh roots in warm rooms, to obtain 

 constant reproduction, it will occur more frequently 

 that the want of food in the cold season will kill the 

 gemmans-phase, or oblige it to undergo the last 

 metamorphosis, and then become what I call the 

 Pseudogyna pupifera. 



This last name has been criticised more than once. 

 I would indicate by it the form which produces the 

 sexuated insects. I wished to establish by the word 

 pupifer that it is not an egg t but a true pupa or 



VOL. iv. 5 



