444 ANNUAL REPORT OF NEW- YORK 



HICKORY. LEAVES. 



AFFECTING THE LEAVES. 



1. Forming galls and other excrescences. 



&.63.. Hickory-stem gall-louse, Pemphigus CarycBcaulis, Fitch. (Ilomop 

 tera. Aphidae.) 



Forming bullet-like galls, hollow, green and of a leathery tex- 

 ture, upon the leaf stalks and succulent young shoots, with tlie 

 walls of the cavity inside covered with minute white and yellow 

 lice; the perfect, winged insect not yet discovered; the gall sub- 

 sequently turning black, opening and becoming cup-shaped. See 

 Transactions, 1854, p. 859. 



164. Hickory-vein GALL-LOUSE, Pemphigus? CarycevencB, new species. 



Forming plaits in the veins of the leaves, which project up 

 from the surface in an abruptly elevated keel-like ridge upon the 

 upper side of the leaf and with a mouth opening on the under 

 side, the lips of which are woolly and closed. 



Although the Aphis which produces these plans in the veins of 

 hickory leaves is unknown to us in its winged state, its work will 

 suflS.ce to distinguish it from other species. The plaits occur 

 mostly near the middle of the leaf, upon one side of the mid-vein, 

 occupying the bases of the lateral veins, two or three of which 

 are commonly enlarged into these excrescences or galls, which jut 

 up in keel-like ridges from a quarter to a half inch in length. 

 These ridges are of a pale yellow color, turning brown and be- 

 coming dry and dead after a time, and frequently before they 

 perish the portion of the leaf between them withers and turns 

 brown, in which case the inhabitants of the gall forsake it, being 

 no longer able to obtain a due supply of nourishment from its 

 walls. The lips of the mouth which opens on the under side of 

 the leaf are covered with white or pale tawny yellow wool. They 

 are pressed together, but a small orifice is open at their outer end, 

 through which some of the young lice frequently crawl from the 

 interior of the gall and station themselves upon the under surface 

 of the leaf by the side of the mid-vein. The lips are readily 

 drawn apart, exposing the cavity wdthin, the walls of which are 

 covered with minute wingless females and their eggs and young. 

 The females are egg-shaped, broadest anteriorly and tapering 

 behind to an acute but not an attenuated point. They are 0.03 



