42 MOSQUITOES OF NORTH AMERICA 
“The labium has for function, for the most part, the protection of the fine 
setee which form the true piercing organ of Culex. In the females of Culex 
proper, the protective sheath is formed by the labium alone. When the mosquito 
has found a place which suits its taste for piercing, it plants its labelle firmly 
upon the spot, and a moment later the labium flexes backward in its middle, the 
sete, firmly grouped together, remain straight and enter the skin, while the two 
labellee guide them, much as a carpenter guides his bit with his fingers while 
boring a piece of plank. When the sete of Culex have entered the skin to nearly 
their full length the labium is bent double beneath the body of the insect, the 
labellee still holding the base of the sete at the point where they enter the skin. 
When the mosquito wishes to withdraw the sete it probably first withdraws the 
two barbed maxille beyond the other sete, that is, so that their barbs, or 
papille, will be kept out of action by the mandibles and hypopharynx; then it 
readily withdraws the sete, perhaps aiding their withdrawal by the muscles of 
the labium, for, during the process of extracting the sete from the skin, while 
they are slowly sinking back into the groove upon the upper side of the 
straightening labium, the mosquito keeps the labelle pressed firmly upon the 
skin. 
“The mouth-parts of Culex, as above described, are suspended under a 
clypeus, or epistom, which is figured from the side in fig. 1, c; from above in 
fig. 2, c; in length-section in fig. 11, c; and in cross-section in fig. 9, ¢. This 
clypeus is the hood-shaped forward continuation of the lower part of a A-shaped 
piece of chitin which forms the framework of what may be termed the ‘ face’ of 
Culex; right and left of the upper portion of this framework pass out the an- 
tennal nerves, the antenne being supported by the framework itself. 
“ The pharynx (fig. 11, p), the tubular continuation of the epipharynx above 
and the hypopharynx below, as it passes backward, beneath the centre of the 
A-shaped framework, turns somewhat upward, is narrowed to the valve pre- 
viously described, then widens slightly again, and, as cesophagus (fig. 11, oe) 
passes through the cesophageal nerve-ring, in which it is supported by three 
delicate chitinous rods, which lie, one longitudinally on its ventral surface, and 
two to the right and left on its dorsal surface. Just posterior to the cesophageal 
nerve-ring, directly above the nerve-commissure which connects the infra- 
cesophageal ganglion with the first thoracic ganglion, the cesophagus suddenly 
expands into an cesophageal pump, or bulb, the longitudinal section of which is 
shown in fig. 11, 6 ; the cross-section in fig. 10, 6. This bulb, which is the chief 
sucking organ in the female Culex, and which I have found in no other dipteron, 
is supported by three longitudinal chitinous rods, which are stouter continua- 
tions of the three rods supporting the cesophagus through the nerve-ring. These 
rods (fig. 10,7) have between them chitin-plates (fig. 10, +) which are suspended 
from the rods by elastic membranes. On the dorsal plate is inserted a double 
muscle, or a pair of muscles (bm), the origin of which is in the dorsal 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 the eyes. By the simultaneous contraction of 
these muscles (bm and bm’), the lumen of the esophageal 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 can not 
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, although, since Swammerdamm’s time, the 
