1882 .] 
395 
[Scudder. 
ably a straighter inner border ; its externomedian area is much 
less extensive and has fewer and simpler branches. 
When we come to its nearer allies we shall find it harder to 
point out sharp and decisive distinctions from the wings alone. 
E. russoma is known only by its front wing and is of the same 
size asE. mazona; the species differ however in their proportions, 
E. mazona having a much slenderer wing with a less strongly arcu- 
ate costal margin. In E. mazona the mediastinal area is consid- 
erably larger, the scapular of a correspondingly diminished ex- 
tent with far less dichotomizing branches; so too, the externo- 
median area is of less extent both basally and on the margin, and 
has an extremely simple set of offshoots, while their arrangement 
is complicated and their number much greater in E. russoma; 
finally in E. russoma the internomedian area diminishes steadily 
in width, that is, the main vein has a nearly straight course 
beyond its basal curve, while in E. mazona it is apically produced 
and the marginal extent of the area greatly increased by the 
arcuate course of the main vein, which takes a longitudinal asjiect 
in the apical half of the wing. Perhaps no one of these points by 
itself would warrant separation, unless it were the shape of the 
wing, which is made up of several elements ; but their combina- 
tion is certainly sufficient to warrant belief in their entire distinc- 
tion. The more so since we find the wing still more closely 
allied to that of E. carbonaria, from which, however, it is distin- 
guishable at once by its entirely different pronotum ; this alone 
should make us hesitate to group together in one species as E. 
Geinitz has recently done, wings which resemble each other but 
have certain clear points of distinction. The pronotum of E 
carbonaria is described by Germar as of equal breadth and length 
with a nearly parabolic form, but with the base strongly arcuate ; 
that of E. mazona on the contrary has the front margin nearly 
semicircular, the posterior gently arcuate and the whole much 
broader than long. The wings, furthermore, show the following 
differences: The mediastinal branches in E. mazona are less fre- 
quent and much less frequently forked ; the scapular area is a 
little less extensive, and in particular is not nearly so broad in 
the middle of the apical half of the wing and does not so nearly 
reach the tip ; the externomedian area, on the other hand, is a 
