390 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
The ocelli, three in number, are arranged in the form of a tri- 
angle. Each of the two posterior is situated on the upper portion 
of one of the ocellar plates, while the anterior is located at the 
head of the frontal fovea, within the angle formed by the two 
oblique arms of the epicranial suture. 
On the vertex, immediately beyond the ocellar plates and 
posterior ocelli, is a well-defined quadrangular plate which 
extends to the posterior margin of the head and forms the pos- 
terior area of the median plateau. This plate, vertex plate, is 
more or less transversely convex and is wider than long, although 
sometimes, as is the rule in verticalis (Say), the difference is very 
slight. It is very often slightly carinate medially and longi- 
tudinally. 
The cheeks or genae occupy the lateral portions of the head 
behind the compound eyes. Each cheek bears at its terminus 
below a semichitinous membranous region by means of which 
the mandibles articulate with the head. 
The mandibles are broad basally, and are gradually attenuated 
toward the apex, ending pointed^. They may be described as 
strong, stout curved hooks. Their inner face is toothed. The 
basal portion of the outer face is as a rule in part or entirely rather 
coarsely punctate, and well covered with long, sub-erect, whitish 
hairs which have their origin in the punctures. 
The lab rum has its origin beneath the clypeus and, as stated, 
is more or less overlapped by it. Its lateral and lower margins 
are free and rest upon the mandibles. The latter margin is 
always rounded, but varies in degree from rather broadly, through 
subacutely, to rather acutely, although the last condition is com- 
paratively rare. The anterior margin bears a dense fringe of 
short golden hairs. The surface of the labrum is, as a rule, more 
or less sparsely punctate, and like the clypeus is sparsely covered 
with long, whitish and sub-erect hairs. 
The hind aspect of the head is concave. In its upper medial 
portion occurs the approximately rectangular occipital foramen. 
Immediately above the foramen occurs a quadrangular sclerite 
(broader above than below) to which, in this paper, the term 
occiput has been restricted; its lateral bounds or sutures are in 
line with the lateral limits of the vertex plate on the vertex. Usu- 
ally, however, these sutures are obsolete. Situated laterally to 
