A"o. 1.] RILEY AND MONELL OX APHIDID.E. 9 



compared. The foUowiug- are the more important differences, least sub- 

 ject to variation, between the winged females of idmi as compared Avith 

 those of americana: ulmi is a longer- winged species, averaging 7.3'"'" 

 in expanse ; the abdomen, wing- veins, and stigma are darker ; the termi- 

 nal distance between 1st and 2d discoidals slightly greater ; the 3d joint 

 of antenniB is relatively longer; the annulations are less deep and more 

 numerous (those on 3d joint averaging. 30) ; joints 5 and 6 are smoother, 

 i. e., -without annulations, but they are more setous ; joint 5 is shorter 

 than 4; the apical, narrowed part of Cth joint is relatively longer and 

 more pointed ; the subcostal vein of hind wings is less straight ; the 

 cubital vein is often continuous to very near the subcostal, while I 

 have not found any tendency of the kind in americana, the tendency 

 being in the opposite dnection, or to become shorter 5 the 2d discoidal 

 of hind wing's shows a tendency to fork ; the booklets on costa of hind 

 wings are 3 in number, while in americana there are normally 4;* the 

 legs are more setous. 



COLOPHAf ULMICOLA (Fitch). 



[Forming cock's-comb-like galls (Fig. 2, a) ou tlie upper surface of tlie leaves of 

 Vlnius americana, the galls appearing witli the opening of the leaves, and turning 

 brown and black in late summer. ] 



Another very common gall, which may be called the Cock's-comb Elm 

 Gall {ulmi-ulmicola), is also found on the White Elm, and particularly, 

 as in the case of the x)revious gall, on young trees. It was well de- 

 scribed by Fitch I as an " excrescence or follicle like a cock's comb, aris- 

 ing abruptly on the upper side of the leaves, usually one inch long 



* These hooklets get so easily broken otf that they are not to be relied on ; yet the 

 normal number on most of the Femjihiginw I have examined is 3, while in HormapMs 

 there are but 2. The fact that in So. americana there are 4 is therefore interesting, 

 and of some value in this connection. 



t The bibliograj)hy of this species very well illustrates the confusion that too often 

 surrounds the prox>er determination, not only of insects of this family, but of all orders. 

 It is due to three causes, not easily removed : 1st, the miserably insufficient nature of 

 the earlier descriptions and definitions ; 2d, the isolation of the earlier English ento- 

 mologists from those of the continent, and the dual nomenclature that has arisen from 

 independent work ; 3d, the want of a common ground for generic characterization. 

 Walsh referred the species to Thelaxes, which has, however, 5-jointed antennae. 

 Vacuna, Heyden, is synonymous with Thelaxes, though Walker would restrict the for- 

 mer to alni, Schrank, and the latter to dryopliila, Schrank ("The Zoologist," London, 

 February, 1870, ji. 2001), without i)ointing out generic differences, as the want of a fork 

 in the cubital vein in Koch's figure is clearly an error of the artist. Mr. Monell founded 

 the genus Coloplia for ulmicola on the fact that the antennaj of the winged female are 

 6-jointed. Such a difference can hardly have generic value when we find ulmicola oc- 

 casionally with but five antennal joints, and (if Huxley is correct in his determination) 

 dryophila sometimes with six (Trans. Linn. Soc. xxii, j)p. 203, 234). But, taken in 

 connection with the fact that ulmicola is a flocculeut species, the true female producing 

 but oue large egg, while dryophila is without flocculence, the female (according to 

 Huxley) laying many eggs, Colopha, considering ulmicola as the type, may be accepted 

 as a good genus. 



t Fifth EeiJort on the Noxious Insects of N. Y. § 347. 



