PERGANDE — NORTH AMERICAN PHYLLOXERINiE. 1 87 



migrants, whereas in the majority which were opened, only the 

 stem-mother and sexes were found. In the case of another 

 species numerous pupse were found with the old mother and but 

 two or a few winged migrants in but a very few galls ; in all of 

 these galls, occupied by the pupse, were also observed large num- 

 bers of the sexes, as progeny of the pupse; whereas in Ph. c- 

 vence Fitch, all of the sexuparse, which usually are winged, are 

 wingless, resembling in this respect the stem-mother. 



The conclusions arrived at are that, as a rule, the great majority 

 of the species produce large numbers of the migratory form and 

 that but few exist in which the stem-mother or pupse are able to 

 produce a sexed generation, and that but occasionally some 

 migrants are developed to guard against the possibility of exter- 

 mination. 



Since the species treated of in this paper comprise but a fraction 

 of those inhabiting the United States, there remains still a large 

 field for fruitful investigation which may amply occupy a lifetime 

 of those selecting it as a specialty. 



In order to facilitate the study of the known species, inhabiting 

 hickory trees, I have divided the various galls into groups, based 

 principally on the location and shape of the galls on the parts 

 infested. 



