618 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



the entire cavity of the outer sliell. The number of these cells varies 

 according to the size of the gall, but is rarely reduced to a single one. 



The full-grown pupa always leaves the gall through the apical open- 

 ing, and in doing so has to saw its way out through the top of the inner 

 core. 



The gall usually occupies the entire petiole, but in rare instances a 

 small portion of the latter is visible between the gall and the twig. 



37. P. {Blastophysa) celtidis-gemma Riley. — This gall is briefly re- 

 ferred to but not named by Osten Sacken (1. c, pp. 422, 423.) It is 

 much smaller than the preceding, very variable in size, and of irregu- 

 lar shape, but always bud-like, and looking as if formed by the con- 

 glomeration of a number of rounded nodules which are separated from 

 the adjoining ones by shallow furrows. Color varying from light red- 

 dish-brown to dark brown or the color of the twig; surface of the 

 young gall usually covered with a dense matting of white woolly hairs, 

 which in the more mature gall are more or less completely lost. As in 

 the preceding species, the gall is hard and woody, but entirely closed. 

 It is usually opaque, rarely a little shining, the surface indistinctly 

 sculptured, but occasionally roughened by adhering particles of the 

 scales of the original bud. It has no inner core, and the cavity is 

 entirely filled with the cells, which vary from one to eight in number. 

 The outer wall is never more than one millimeter thick, often less, while 

 the walls dividing the cells are sometimes very thin and sometimes even 

 thicker than the outer wall. The gall occurs only on one-year-old twigs, 

 and is formed by the young larva? settling on and sinking into -such 

 buds as would normally produce a new twig the ensuing year. Each 

 mature pupa saws its way through the wall of the gall in spring and 

 changes to imago immediately after issuing. 



38. P. celtidis-vesiculum n. sp. — This gall appears upon the upper side 

 of the leaf merely as a flat blister of yellowish or reddish-yellow color 

 and of irregular outline. It is generally rounded, but often influenced 

 and limited by the larger leaf nerves, which are rarely crossed by the 

 gall. On the under side of the leaf the gall is still less conspicuous, 

 and is visible only as a discolored spot with a small rounded nipple in 

 the center. The sculpture of the surface of the gall is the same as that 

 of the leaf, and the walls are not thickened. 



This gall often occurs in very large numbers on one and the same 

 leaf, crowding one another, and often confluent. The full-grown pupae 

 break through the wall of the gall either on the upper or lower side of 

 the leaf. The species is most readily recognized from the very incon- 

 spicuous appearance of the gall, and more especially from the fact that 

 it is the only one which is hardly developed on the under side of the 

 leaf, whereas all the other leaf-galls assume there a more or less con- 

 spicuous form. 



39. P. celtidis-asteriscus n. sp. — This gall, on the upper side of the leaf, 

 is very similar to the foregoing species, i. e., represented only by a barely 

 raised, blister-like spot, distinguished from the surface of the leaf mainly 



