616 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



not quite attaiiiiug apex of second abdominal joint, those of under wings slightly- 

 projecting internally and posteriorly. Abdomen composed of eight joints, widest at 

 middle, gradually narrowing anteriorly and very strongly posteriorly ; anal joint 

 drawn out in a horny process; first joint very short, second twice as long as the 

 first, the following three joints still longer, the fourth being the longest and widest; 

 dorsal and ventral sides of joints 2 to 4 separated by a rounded lateral bulging ; 

 dividing sutures of segments 1 to 5 very deeply impressed; last three joints much 

 less distinctly divided, more horny, and of darker color, rapidly narrowing posteri- 

 orly, and provided dorsally with a number of black, backwardly directed, triangular 

 teeth, arranged as follows: Sixth joint at middle of hind margin with two or three 

 very small teeth placed transversely and with no lateral teeth; seventh joint at 

 middle of hind margin, with a transverse row of four teeth, and on each side with 

 two or three (often obsolete) teeth or tubercles; anal joint with the horny process 

 about half as long as the joint, and nicked at the tip, while at base of process on 

 each side a lateral row of four small, closely placed teeth extends to the under 

 side, and finally on the disk of the joint three teeth triangularly placed, the poste- 

 rior being the largest; behind this group and just ab ove the base of the process is 

 another tooth nicked at tip. 



The pup0B of the other species differ mainly from the above descrip- 

 tion in the smaller size, the form and length of the anal process, and in 

 tlie number and arrangement of the abdominal teeth. That of P. 

 c.-gemma alone has some other distinguishing characters. 



The young larvpe of all species are of a more uniform pale color with 

 less developed wing-pads and the segmentation of the abdominal jointB 

 much less evident; they are further distinguished by the smaller num- 

 ber of antennal joints and the weaker development of the abdominal 

 armature. 



The galls produced by the species of Pachyiisylla may be distin- 

 guished as follows: 



Polythalamous (very rarely monothalamous) galls, never on the surface of the leaf, 

 always singly. 

 Large gall on petiole and involving the basal portion of the leaf; usually some- 

 what reniform in shape, and with an opening near the tip. 



P. venusta O. S. 

 Smaller gall on the twig, bud-shaped, and without opening. 



P. c.-gemma Riley. 

 Monothalamous galls, always on the leaf, usually occurring in great numbers. 



Gall blister-like on both sides of the leaf and hardly raised above the surface of 



the leaf P. c.-vesicuhim n. sp. 



Gall on the under side of the leaf, not blister-like, more or less raised above the 

 surface and assuming various shapes. 

 Gall on upper side of leaf, blister-like and not forming a depression ; on 

 undersideof leaf star-shaped or flower-shaped.. P.c.-asimscMsn. sp. 

 Gall on upper side of leaf represented by a depression. 



Gall on upper side of leaf, with the outer rim alone depressed, the 

 central portion slightly raised and provided with a median spine; 

 on under side of leaf wart-like, much flattened, with a more or 



less pronounced depression at middle P. c.-umbilicus n. sp. 



Gall on upper side of leat represented by a cup-like depression, the outer 

 rim sometimes elevated. 

 Gall very large, mammiform without depression or rim on top, 

 usually not pubescent, sometimes with slight down at base. 



P. c.-mamma Riley. 



