1(38 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
mass and there are nine abdominal joints, of which the eighth bears 
the respiratory siphon and the ninth four anal valves and a ventral 
keel of setae. Under the scope of this paper the head alone requires 
detailed description. 
The head of the Culex wriggler (pi. 15, fig. 29-32) is flattened in 
the dorso-ventral plane. Forward of the antennae it narrows. 
Behind them its cross section would resemble that of a watch, a 
flattened oval. The dorsal surface is the more convex, descend¬ 
ing rapidly in the rear, more gently at the sides, and with a 
comparatively steep slope forward from the antennae. The ante¬ 
rior margin of the head is bounded by a border line of thickened 
chitin (bord l) beyond which a shelf-like fold projects. The shelf 
bears two simple setae. The investing cuticle of the top of the head 
is strong and is reinforced by two thicker scythe-shaped areas (sea) 
which extend backward from the antennae. At pupation the cuticle 
splits along the inner margin of either area to the occipital foramen. 
On the ventral side of the head the transverse line (tr l) separates 
the pre- from the post-antennal region. This boundary consists of a 
narrow-linear band of dark, thickened chitin laterally and a low 
transverse fold mesially. Heavy cuticle extends over the post-anten¬ 
nal ventral region of the head and is traversed by two narrow-linear 
“lines” of dark, thickened chitin which pass from the transverse 
line to the border of the occipital foramen. These divergent lines 
support the ventral ends of the tentoria, the black, triangular, mental 
sclerite, and furnish a point of origin for the depressors of the 
antenna (ant m) and other muscles. At pupation the ventral head 
cuticle splits in the midline from the occipital foramen to the trans¬ 
verse line. 
The relations of the pre-antennal region of the head are hard to 
describe. As noted, the dorsal surface is convex and heavily chiti- 
nized. The ventral face slopes sharply inward and downward 
toward the entrance to the pharynx, a point almost in the center 
of the head. Thus the pre-antennal region is in reality a broad ros¬ 
trum which overhangs the mouthparts, situated near the transverse 
line below, slightly forward of the entrance of the pharynx (pi. 14, 
fig. 26). Its cross section would be the segment of a circle, the 
arc being represented by the convex dorsal surface. In the mid- 
ventral line, about halfway between the anterior shelf-like fold and 
the entrance of the pharynx, a crest is formed. This bears four 
