244 Bulletin of Laboratories of Denison University. [Voi. xi. 
In this paper I consider fifteen species, which seem to fall 
naturally into five groups. I offer the following key to aid in 
separating them. The dark colored apex of the wing is consid- 
ered as a band. 
I. Seventh and eighth abdominal segments and forceps of the 
male much elongated, no horn on sixth segment ; sub- 
costa uniting with the costa far before the pterostigma, 
Group lugubris. 
Wings black with narrow hyaline cross bands, lugubris. 
Large species, wings yellow with three wide black 
bands, pterostigmal band not forked behind, nuptialis. 
Smaller species, pterostigmal band forked behind, 'rufa. 
II. No horn on sixth abdominal segment of the male, wings 
with irregular markings, not usually in the form of bands. 
Group nehulosa. 
1 . Sub-costa uniting with the costa far before the pterostigma, 3 . 
Sub-costa uniting with the costa at the pterostigma, 2. 
2. Large species, pterostigmal band of wing entire, latipennis. 
Smaller species, rarely with any entire bands on the wings, 
nebulosa. 
3. Radial vein curves inward to form the pterostigma, maculosa. 
Radial vein nearly straight at pterostigma, . . banksii. 
III. Horn on sixth segment of the male, wings hyaline, with 
three entire black bands on the forward pair ; from side 
view a prominent elevation apparent on the basal part 
of the claws of the male forceps, Group subfmcata. 
Elevation on the basal part of the claw of the male forceps 
rounded, about one-half as long as the claw ; wings 
rather narrow, ..... signifer. 
Elevation on the claw of the male forceps oblong, reaching 
for more than half the length of the claw ; wings 
wider, . . . . . ^ . subfurcata. 
IV. Horn on the sixth segment of the male, wings yellowish 
with three black bands, basal band rarely interrupted. 
Group americana. 
Bands on wings regular, wings wide and regularly rounded 
at the end, 
amencana. 
