PSTCSTE. 239 
shaped framework, turns somewhat up- 
ward, is narrowed to the valve previously 
described, then widens slightly again, 
and, as oesophagus (fig. 11, 0e) passes 
through the oesophageal nerve-ring, in 
which it is supported by three delicate 
chitinous rods, which lie, one longitudi- 
nally on its ventral surface, and two to 
the right and left on its dorsal surface. 
Just posterior to the oesophageal nerve- 
ring, directly above the nerve-commis- 
sure which connects the infraoesophageal 
ganglion with the first thoracic ganglion, 
the oesophagus suddenly expands into 
an oesophageal pump, or bulb, the lon- 
gitudinal section of which is shown in 
fig. 11, 6; the cross-section in fig. 10, b. 
This bulb, which is the chief sucking 
organ in the female Culex, and which I 
have found in no other dipteron, is sup- 
ported by three longitudinal chitinous 
rods, which are stouter continuations 
of the three rods supporting the oeso- 
phagus through the nerve-ring. These 
rods (fig. 10, 7) have between them 
chitin-plates (fig. 10, ¢) which are sus- 
pended from the rods by elastic mem- 
branes. On the dorsal plate is inserted 
a double muscle, or a pair of muscles 
(bm), the origin of which is in the dor- 
sal part of the chitinous shell of the 
head. Each of the lateral plates has 
inserted on it a muscle (bm’), the origin 
of which is in the chitin of the lower 
lateral regions of the head. The origin 
of each of these muscles is in the so- 
called occipital region of the head, that 
is, behind theeyes. By the simultaneous 
contraction of these muscles (mand bm’), 
the lumen of the oesophageal bulb is 
enlarged, and the blood flows into the 
bulb from the pharynx, and, upon their 
relaxation, the elasticity of the chitinous 
walls of the bulb drives the blood, which 
cannot return to the pharynx because of 
the closing of the valve at v (fig. 11), 
into the stomach. 
IN THE MALE. 
The mouth-parts of the male of Culex 
have not been described, as far as I 
know, with any degree of accuracy 
though, since Swammerdamim’s time, the 
males have been distinguished from the 
females, by all scientific entomological 
writers on the subject, by means of their 
feather-like antennae and maxillary palpi. 
The proboscis of the male of Culex 
pipiens, the only species the male of 
which I have studied, is slightly longer 
and slenderer than the corresponding 
organ in the female. The setae are 
fewer in number and less completely 
sheathed by the labium than in the fe- 
male; they consist of a well-developed 
labrum-epipharynx and two slightly de- 
veloped maxillae. The mandibles are 
absent, and the hypopharynx coalesces 
with the labium (fig. 12, 4 and/). The 
labium and maxillary palpi are more 
densely covered with hair and seales 
than they are in the females, and they 
contain muscles ; the other mouth-parts, 
the setae proper, are naked, chitinous, 
and contain no muscles. In comparative 
length the mouth-parts may be arranged, 
longest first: maxillary palpi, labium 
and labrum-epipharynx, maxillae ;—in 
comparative size they may be arranged, 
largest first: labium, maxillary palpi, 
labrum-epipharynx, maxillae. The rel- 
ative position of the mouth-parts of. the 
male is different from that in the female 
(compare fig. 8-9 with 15-15) in that 
rudimentary maxillae are 
al- 
the short, 
