HACKBERRY PSYLLIDS. 



617 



Monotbalamous galls — Coutinued. 



Gall smaller, seini-globular, sessile, covered with long soft hair and 

 without impression P. c.-puhescens n. sp. 



Gall smaller, globular, subsessile, with a small impression at toj), 

 not pubescent F.c-globulus n. sp. 



Gall smaller, not pubescent, sessile, wider than high, very much flat- 

 tened on top, and here usually with two concentric elevated rims, 

 and provided with a central nipple P. c-.ciicurhitau. sp. 



Gall smaller, not pubescent, less sessile than the preceding, higher 

 than wide, around the sides near top with longitudinal sulci, the 

 top cup-like, depressed, and without central nipple. 



P. c.-cnrcurMta var.? 



The following characteristics of the galls are condensed from more 

 elaborate descriptions, which I hope to publish in a more complete 

 I)aper on the biology of the North American Psyllidai, 



36. P. venuata Osteu Sacken (Stett. Eut. Zeit., 1861, p. 422).— Gen- 

 erally globular, but often more or less irregularly ovoid, or even elong- 

 ate. Color varying from pale buff to brown ; surface opaque, with scat- 

 tered, small, flattened postules. Diameter of globular form varying 

 from 7 to 20""", The gall consists of an outer shell and an inner core, 

 which can easily be separated upon cutting the gall open. The outer 



Fig. 201. — Gall of Pachypgylla venusta: a, gall fully 

 formed; 6, same forming; c, same in section, natural .size. 

 After Riley. 



shell is very hard and woody, varying in thickness from 1 to 3""". The 

 apical portion of the gall has on one side a slit which is deepest and 

 widest at the tip and connects here with the funnel-like, twisted, basal 

 portion of the leaf. This slit exposes to view the inner core, which con- 

 sists of the very thin and brittle walls of the irregular cells which fill 



