374 [February 
meiits transversely depressed at base, and the apical segments of the 
males armed with spines. 
Sect. 2, containing those species which are short and very robust, 
the body not hairy, the wings mostly fuscous, the second recurrent 
nervure passing a little beyond the apex of the second submarginal 
cell, the abdomen short, glossy, and very convex above, the segments 
not depressed at base, and the apical segments of the males not armed 
with spines. 
Section 1. 
I. A. emarginatum, Say. 
MegacMle emarginata, Say, Long’s 2nd Exped. ii. p. 352, 9 (1824). 
Female .—Head black, densely punctured, thickly clothed with rather 
long pale hairs, which are sparse on the clypeus; a small ferruginous- 
yellow spot on each side of the vertex over the eyes. Antennae black. 
Thorax black, opaque, densely and finely punctured, thickly clothed 
with pale hairs ] the tubercles, anterior part of the tegulae, and four 
spots on the posterior margin of the scutellum.—the extreme basal 
ones being the smallest, yellowish-white. Wings hyaline, nervures 
fuscous. Legs black, clothed with pale hairs, especially on the tibiae 
and tarsi; a yellowish-white vitta on the exterior edge of each tibia ; 
tarsi clothed within with rufo-fuscous pubescence. Abdomen convex, 
finely punctured, black, somewhat shining; a yellowish-white fascia 
near the apical margin of each segment, very slightly interrupted on 
the disk except that on the basal segment, and more or less emarginate 
on each side anteriorly, the fascia on the basal segment is deeply indent¬ 
ed posteriorly ; ventral scopa yellowish-white. Length 4^ lines. 
Male .—Resembles the female, but differs as follows:—the clypeus, 
the face on each side of the clypeus and the mandibles are yellowish- 
white ; the posterior margin of the scutellum has only a narrow yellow¬ 
ish-white line on each side of the middle; the vittm on the exterior 
edge of the tibiae are interrupted on the anterior and intermediate 
pairs, and reduced to a short line at the base of the posterior pair; 
the wings are faintly tinged with fuscous ; the fasciae on the abdomi¬ 
nal segments are broadly, deeply and somewhat squarely indented an¬ 
teriorly, the indenture on each side of the basal segment extending 
entirely through and dividing the fascia into four spots, a small ojie 
each side of the disk and a large one at each extreme side; the fascim 
on the fourth and fifth segments are scarcely interrupted on the disk; 
