162 
Journal New York Entomological Society. [Voi.iv. 
'j 
• ments convex, those of the thorax broad, regularly convex, smooth, not 
thickened posteriorly; quite different from those of the abdomen. The 
abdominal segments shorter posteriorly above than the thoracic ones. 
The posterior portion of the segment thickened so as to form a rounded 
tubercle, which is very prominent and distinct when the body is much 
curved. This portion is thickened; the tuberculous portion is much 
smaller in proportion to the rest of the segment than usual in Apidse. 
The tip is quite extensible, subacute, terminating in a small knob-like 
portion. Genitals not apparent, the skin being too thick. A few sparse 
long hairs over the body, in which respect this genus differs from those 
of the other families, and it differs in its elongated extensible tip, though 
it is probable that this part became contracted in alcohol; when con¬ 
tracted, the terminal segment is rather square, not being rounded at the 
tip. Length of body .25 inch. 
The larva burrows in the dust made by the larva of an ^Egeria in 
the pith of the Spiraea, spinning little thin silken cocoons, half a dozen 
of them occurring in a space of the stem an inch long, lying loose in the 
galleries, some lying across the stem, and others lengthwise. The 
cocoon is very thin and slight compared with that of Crabro sex-macu- 
lata , being composed of only a few silken threads. Found April 18th. 
Pupa. _9. The middle joint of the antennal scape is bent at right 
angles to the flagellum, the third joint being continuous with the flagel¬ 
lum, while in Pelopoeus flavipes it is more oblique, as the front of the 
head is longer and more horizontal, while in Rhopalum it is at right 
angles to the longitudinal axis of the body. The head is more vertical, 
less flattened on the pectus of the thorax. Mandibles thick and stout, 
convex, much more so than in Pelopoeus . The antennae do not quite 
reach to second pair of trochanters; in Pelopaus , they reach beyond 
the third pair; they also reach the tip of the maxillary palpi, which in 
Pelopoeus reach half their length. They rest close to each other along 
the median line of the body. The maxillary palpi are straight, not 
slightly elbowed near the base; they reach to the tip of the 
antennae; the labial palpi are proportionately longer, reaching nearer 
the tip of the maxillary pair than in Pdopceus, and less elbowed or 
angulated at tip. The anterior tarsi end just before the middle trochan- > 
ters; the middle tarsi terminate near the end of the pedicel of the ab¬ 
domen, and the third tarsi end near the middle of the third abdominal 
segment. Tip of abdomen with the terminal tergite very acute, elon¬ 
gated, extending beyond the ovipositor; the last sternite is oblong, 
flanked on each side by two cylindrical pieces. On the head between 
