462 
[March 
species of Phylloxera (Aphidae) which form very distinct galls on the 
black Or shag-barked hickory, Ph. caryeefolise Fitch, Ph. caryseglohuli 
Walsh, and Ph. (^pemphigus) carysecaulis Fitch, which last was only 
known to Dr. Fitch in the gall and was referred by him to Pemphigus., 
but both Baron Osten Sacken and myself have obtained from it the 
perfect insect which is scarcely distinguishable from caryseglohuli. Fi¬ 
nally, there are certainly 3 and probably 6 species of Byrsocrypta 
(Aphidse) forming distinct galls on the cottonwood (Populus angulata) 
and other poplars, viz., B. (^pemphigus) populicaulis Fitch, B.pseudo- 
hyrsa Walsh, and B. vagahunda Walsh, which last, since the descrip¬ 
tion was published, I have ascertained to inhabit smooth, hollow, green 
galls at the tips of the young shoots of the cottonwood, shaped much 
like the garden flower known as “cockscomb,’^ and about 1—inch 
in diameter. I have recently seen similar galls similarly situated on 
the Balm of Grilead (P. balsamifera.) 
The same propensity to inhabit certain genera of plants has been 
observed in many other genera of Insects that do not produce galls. 
For instance, Dryocampa affects the oaks, Vanessa and allied genera 
the nettles, Hipparchia the grasses, and Argynnis the violets. These 
facts have a clear significance on the theory of the Derivative Origin of 
Species; on the Creative Theory they are inexplicable. 
true galls, but Ps. huxi and also Lima juncorum produce deformities upon 
leaves ; and there is no Psyllade genus, so far as I am aware, to which these 
insects can be referred. For the benefit of those who, more fortunate than my¬ 
self, have access to good Entomological Libraries, it may be added here that 
Baron Osten Sacken writes me word, that there is a Paper on the generic ar¬ 
rangement of Psylladse by Foerster, in Rheinloendsche Verhandlungen, and an¬ 
other by Flor, in Bulletin des Natur. de Moscou, 1861, Art. 2. 
