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forked or cleft at apex. Fitch's single male specimen was quite 
naturally referred by him to the genus Janus, as formerly understood, 
and what is unquestionably his veritable type specimen, I was fortu- 
nate enough to discover in a badly damaged condition, but still recog- 
nizable, among the Tenthredinidse of the Fitch collection now in the 
National Museum, enabling me to remove any doubt as to the identity 
of the species reared by Mr. Allis with Jfaviventris. Since the discovery 
by Fitch of this specimen, no other examples of this species have come 
into the hands of entomologists, until the rearings of Mr. Allis, neither 
Oresson nor Norton having seen the insect. Fitch's description is as 
follows : 
It is a pretty little fly of a shining black color, with'the hind body lemon yellow, 
except at its base, its mouth being straw-colored, and also the hind margin of its 
collar, the base of its wings, a small spot above their sockets, and the fore and hind 
margins of the metathorax. The hind body is narrower than the fore body and 
more narrow and long than in the typical species of this genus, forming almost tWo- 
thirds of the total length of the insect. Its basal segment is black, edged anteriorly 
with straw-yellow, and with a slender line of this color along its middle, ending in 
a large triangular spot. The second segment is also black, except at its hind end; 
and on the sides is a blackish cloud on the sutures of each of the remaining seg- 
ments. The wings are hyaline and glassy, their stigma sooty brown, which color 
extends inward, occupying most of the anterior marginal cell. A faint smoky cloud 
may also be perceived near the middle of the posterior apical cell, and another 
along the margin of the anterior one. The hind feet are dusky. 
This species he called the Yellow-bellied Janus, placing it thus, 
because, as he says, the hind body is cylindrical instead of being 
compressed. 
DESCRIPTION. 
I append a more careful description of both sexes, the female being 
characterized now for the first time. 
Female. — Length, 12 mm ; wing-expanse, 20 mm ; antennae, 28-jointec' ° general sur- 
face body, glistening; head, large, quadrate, black, palpi and mandibles, yellow, 
except reddish-brown tip of the latter, which are also very broad and tridentate, 
the upper tooth longest and middle smallest ; thorax black, with hind margin of 
prothorax, tegulae, spot above base of anterior wings, narrow posterior borders of 
scutellum and post-scutellum of mesothorax, cenchri, large triangular opening in 
metathorax, and area beneath the base of posterior wings light lemon-yellow; wing- 
veins in general brown, costal vein yellow, stigma brown, yellow at either extremity, 
and with sooty patch extending down over one-half the first cubital cell; tips of 
wings very faintly infuscated ; first cubital cell complete ; abdomen, reddish-yellow 
and black; first segment with small lateral black spot at base, narrowly connected 
dorsally ; second and third segments entirely yellow, fourth with black dorsal spot, 
balance black, including sheaths; venter of fifth segment somewhat paler; legs in 
general reddish-yellow, bases of coxae, black; basal one-eighth of tibia lemon, 
yellow, particularly noticeable in the posterior pair; upper tips of hind femora and 
outer three-fourths of hind tibiae and all of hind tarsi, dark brown. 
Male. — Length, 9 mm ; wing-expanse 17 mm ; antennas 25-jointed; markings and 
characters in general as in female, except that the legs are much lighter, the 
anterior pairs being in general pale lemon-yellow throughout, and the hind pair 
much lighter than in female. The wings are decidedly infuscated at outer margin, 
