1/G [Jaiiuary, 



pellier), Querciis coccifera ; the lice which come out o£ these eggs 

 grow very quickly, and, after four moults of five days each, hecome 

 all winged, and fly away from Q. coccifera ; they wander to another 

 kind of oak, Quercus puhescens, and there lay little eggs under 

 the leaves ; the lice which come out of these second eggs grow very 

 slowly, and produce, after their four moults, many generations of 

 apterous lice, all agamoiis. When the month of September arrives, 

 some of these lice (not all) take wing and fly back to Quercus coccifera. 

 Here they do not lay eggs, but little ovoid bodies of two sizes, from 

 which issue, in a very few days, apterous lice wanting a rostrum, but 

 having the sexual parts well formed. These are the males and females, 

 and, after coj)ulation, these last lay each a single large egg, which 

 is the only true fecundated egg worthy of that name ; it passes the 

 winter in the crevices of the oak bark, and gives birth in the spring 

 to the mother louse, which appears in May. 



Thus the Phylloxera, in the course of the year, takes twice a winged 

 form (I speak here only of the oali Phylloxera, the grape one has a 

 rather simpler history) : in the first, its progeniture is agamous, and 

 it has a rostrum ; in the second; it is sexuated, and without a rostrum. 

 The first phenomenon is already known as parthenogenesis ; I call the 

 second one anthogenesis, finding some analogy between the louse con- 

 taining a female and some male pupae, and the flower bud containing 

 the female pistil and the male organs with their pollen. Besides this, 

 there is the exceedingly cui-ious fact of migration from one species of 

 oak to another. 



Now, after having given so far the history of an anthogenetic 

 Homopteron, I think a good many other plant-lice, and more particu- 

 larly, the short-horned ones, Pemphigus, Schizoneura, Tetraneura, &.Q., 

 will prove, some day or other, to be also wanderers from one plant to 

 another, and anthogenetic. 



Also I discover that Pemphigus Boyeri, ccerulescens (grass root-lice) , 

 and Amycla fuscicornis (also a grass root-louse), give sexuated forms in 

 the sprmg. 



Schizoneura corni gives in summer im. agamous, but, in the autumn 

 a sexuated, generation. 



Vacuna dryophila is in the same case. 



Pemphigus spirotheca, the common gall-louse of the poplar, gives 

 now (in December) sexuated individuals. 



I should not be astonished at all, if some ardent follower of ento- 

 mological observations, find out some day that the gall-lice of the 

 poplars, elms, &c., are only the summer form of the grass root-lice. 

 Who knows ? 



Nice : December, 1877. 



