246 [Septkmbet'. 



gall, sufficiently different from that of the other species, to be distinguish- 

 ed by constant characters. The synonymy ot both therefore, although 

 probable, seems to require further confirmation. 



The gall-fly C. q. aciculata has been described 1. c. p. 56. Its anteu- 

 nse are 14-jointed, the last joint being separated from the penultimate one 

 by a suture as distinct as that of all the other joints; the 14th joint is 

 very slightly longer than the 13th, and without any apparent transverse 

 impression. This character, common to C. q. aciculata and to 0. q. cen- 

 tricola (of the oak-apple on Q. ohtusUoha) distinguishes these species at 

 once from C q.manis, spongifica and coccinese, where the last (13th) joint 

 of the antennae is almost twice as long as the preceding, and shows two 

 indistinct transverse sutures, foreshadowing the 14th and 15th joints of 

 the % . The structure of the abdomen of these two groups of gall-flies 

 is also very different. Seen from the side, it appears in C. q. aciculata 

 and ccntricola very slightly convex above, the line of its back not rising 

 abruptly above the petiole; the principal curve in the outline of the ab- 

 domen is on its under side, so that its side-view is not unlike that of the 

 seed of a Dc.wiodium. In C. q. inanis and the two other species, on the 

 contrary, the abdomen, seen from the side, appears as convex above as be- 

 low, its dorsal line rising steeply above the petiole. In the former group 

 the largest or 2nd joint (the petiole being taken for the first) is compara- 

 tively longer, occupying almost f of the length of the abdomen, whereas 

 in the other group (C. q. inanis etc.) it only reaches its middle. These 

 differences prove that these two groups should, in a rational systematic 

 arrangement, form two genera. It is also worthy of remark that both 

 species of one group (C. q. aciculata and centricohi) are produced by au- 

 tumnal galls, and escape either late in the fall, or remain in the gall through 

 the winter, whereas, the species of the other group all belong to venial 

 galls, the gall growing with the leaves and the fly passing through all the 

 stages of its growth between the earliest spring and the end of June. 



To the four oak-apple galls just described, have to be added that of C. 

 q. cenfricola 0. S., on the post-oak (1. c. p. 58, gall No. 4) and that which 

 I found once on Q. nif/ra, the black-jack oak (see 1. c. p. 53, line 14). 

 I have not found it since, but possess in my collection a specimen of a 

 gall-fly, closely resembling C. q. inanis. sponr/ifira and roccincse and dis- 

 tinguished only by a much more distinct punctation of the abdomen, which 

 specimen, if I remember right, was reared from that gall, f Unfortunately 

 I lost the label indicating its origin. ) 



