PHYLLOXERID^E. 71 



Montpellier, and I obtained the winged Pseudogynre in 

 March ; so it is easy to conceive that, according to the 

 climate — and perhaps also to the difference of food and 

 other circumstances, insects usually elsewhere having 

 one brood in the year may have two or more. 



If we consider that we have to deal with the family 

 of insects where, besides the sexual, there is an agamic 

 reproduction, extending perhaps to an infinite series, 

 there is no wonder that in southern climates we find 

 thousands of acres of vineyards destroyed in the course 

 of a year or two. Although we see these insects so 

 alike in form that it is not easy to find plastic cha- 

 racters sufficient to distinguish one from the other ; yet 

 in their biological evolution a tolerable classification 

 may be made as follows : 



On oaks. — Emigrant species. 



From Quercus coccifera to Quercus pubescens. Phyl- 

 loxera quercus, Boyer. 



From Quercus ilex to Quercus sessiliflora. Ph. 

 florentina, Targioni. 



Non-emigrant species. 



Feeding on the bark. Pupifer winged. Ph. cor- 

 ticalis, Kalt. 



Feeding on the leaves. Foundress in a gall. Pupi- 

 fer winged. Ph. coccinea, Heyden. 



Foundress (?). Pupifer wingless. Ph. punctata, 

 Licht. 



First stage unknown. Pseudogyna gemmans in a 

 Swelling of the leaf. Pupifer wingless. Ph. acantho- 

 chermes, Kollar. 



On vines. — Evolution partly aerial and partly sub- 

 terranean. 



First stages all apterous. Pupifer winged. Ph. 

 vastatrix, Planchon. 



M. Lichtenstein closes these interesting remarks on 

 the Phylloxeridse with a warning that much confusion 

 may arise by mistaking the winged emigrants for the 

 second winged generation or pupifer. This last form 

 alone produces the mouthless males and females. 



