72 BRITISH ArHIDES. 



Before dismissing this portion of my subject, I wish 

 to make the following short comment to prevent 

 misapprehension : 



Whilst fully sensible of the value of much that M. 

 Lichtenstein has written on the Peruphiginaa and 

 Phylloxerina3, I would guard myself from a committal 

 to some of the theories he has put forward, such as 

 the periodic migration of Aphides from one food-plant 

 to another; and particularly as to his observations, 

 that certain species feed on the leaves of the oak, and 

 subsequently descend to the roots of grasses for 

 hybernation. I find it the more necessary to make 

 this reservation, since M. Lichtenstein in the ' Comptes 

 rendus ' for December 4th, 1882, uses my name, 

 together with others, as an authority for these points 

 in the economy of these insects. The utmost that I 

 can say is, that though all analogy in other insects is 

 against such migrations, the results of experiments, 

 if rigidly correct, must really control preconceived 

 notions. 



M. Lichtenstein distinctly states that he and his 

 friend M. F. Eichter have bred the winged Tetranewra 

 ulmi from certain larvaa feeding on the roots of 

 Tritirum repens (chien-dent). Of course if this be so, 

 and no mistake has been made in identifying this 

 species, other biologists will soon corroborate observa- 

 tions of such curious habits. I would say for myself, 

 that I have not noted such an economy in the English 

 Tetrancura, Pemphigus, and Phylloxera. I prefer, 

 therefore, for the present, to hold my judgment in 

 suspension. 



Again, where I have used the words " emigrante " 

 and " pupifere," I have done so, to distinguish the 

 first alate brood, which wanders from one tree to 

 another of the same kind ; from the second alate brood, 

 which generally produces the true sexes. I think the 

 word " pupifere " is not a happy one, for it is likely to 

 mislead. Still, as may be seen in a few pages back, 

 M. Lichtenstein has given his matured reasons for 



