1864.] 
461 
like those of C.gallse tinctorise. Again, Westwood says that in Cgnips 
the three sides of the areolet are of equal thickness. (Ibid.') Yet in 
the above specimen of G. gallse. tinctorise, as well as in all N. A. Cyni- 
pidae known to me, I find the terminal vein thicker than the others, 
and Dr. Fitch observes the same thing of all N. A. Cynipidae known 
to him. (W. Y. Rep. II, §309, p. 28.) In all other respects but these, 
sporigifica, inanis, &c., agree well with the characters of Cgnips, and 
unless they are referred to that genus, there seems to be no other de¬ 
scribed genus to which they can with propriety be referred. Hartig, 
it appears, does not consider the number of the antennal joints as of 
generic value, for the species of Aulax Hartig, and of some others of his 
genera, vary in this character. {Proc. Ent. Soc. Phila. II, p. 34, &c.) 
It is remarkable that all our N. A. Cynipidae, as has been observed by 
Dr. Fitch, have the abdomen highly polished and nearly glabrous, while 
G. gallse tinctorise (Asia) has the abdomen opaque and strongly and 
coarsely pubescent. And it is still more remarkable that the % of G. 
nubilipennis Harris, actually has sixteen-jointed antennae. (^See the 
Appendix.^ 
Few things are more striking in the history of the different families 
of gall-producing insects, than the manner in which certain genera are 
almost exclusively confined to certain genera of plants. Authors long 
ago noticed the innumerable species of Ggnips and its allies that infest 
the different species of oak. We learn from Osten Sacken that the 
Cynipide genus Diastrophus affects the bramble both in America and 
Europe, and that the Cynipide genus Rhodites (10 species) is found on 
the rose and only on the rose both in America and Europe. Three species 
of gall-producing Psylladae (Homoptera) have been noticed by him, as 
he has kindly informed me, to inhabit the hackberry, (Celtis occiden- 
talis,) all forming very different galls. One only of these, Psylla (?) 
venusta 0. S. MS., was bred by him to the imago; a second one I have 
myself bred in great numbers, and I can testify to its specific distinct¬ 
ness from venusta, as I have been favored with specimens of the latter; 
the third species is still unknown in the imago.* Again, there are three 
* My insect as well as venusta evidently belongs to a genus distinct from 
Psylla. The antennse are 8-jointed (not 10-jointed) with the 8th joint long and 
idavate. and the .8rd joint the longest; and there are no spurs to the hind legs, 
whereas Psylla has two strong spurs there. No Psylladse known to me form 
