rather than a tube, a tube being formed 
by the pressing of the hypopharynx 
upon its under side. The tube thus 
formed is the channel through which the 
blood, which Culex sucks, passes into 
the pharynx. At its base or proximal 
end the epipharynx is supported and 
moved by strong muscles having their 
insertions on the upper side of its wings 
or lateral portions, and upon the upper 
side of its tube. These muscles extend 
upward and posteriorly, and have their 
origin on the inner surface of the cly- 
peus. (See figs. 9 and 11.) These 
muscles (pm), by their contraction, ele- 
vate, and perhaps slightly retract, the 
epipharynx and the labrum to which they 
are attached. These muscles probably 
aid in suction for when the setae are all 
stuck firmly in the skin, the contraction 
of these muscles would only serve to 
raise the base of the epipharynx from 
that of the hypopharynx; this action 
would tend to produce a vacuum between 
the two (see fig. 9), and thus cause the 
blood to be drawn up in the tube of the 
epipharynx. The probability that these 
muscles aid in suction is augmented by 
the fact, the explanation of which I have 
more fully developed in the part of my 
dissertation devoted to a comparison of 
the mouth-parts and suctorial apparatus. 
in the different families of diptera upon 
which I have worked, that the correspon- 
ding muscles are devoted to suction in 
other flies, which cannot raise their 
epipharynx from their other mouth-parts 
so freely as is seen in fig. 1, and further, 
that in the male Culex, which does not 
possess — as does the female — a pump- 
PST CIE: 
ing apparatus behind the oesophageal 
nerve-ring, these muscles are the ones 
that must serve for suction. The section 
represented in fig. 9 was taken near the 
base of the clypeus; a few sections fur- 
ther on, posteriorly, the channel for the 
passage of food turns upward and then 
backward again, passing in its course a 
place (fig. 11, v7) where its walls ap- 
proximate dorsally and ventrally. This 
narrowing of the walls is probably a 
valve to prevent the return of fluids to 
the mouth during the pumping process. 
The pharynx with its surrounding mus- 
cles in Culex is the equivalent of what 
has been termed the fulcrum in Musea. 
Macloskie“ writes of the fulerum, ‘‘ It 
seems to be general in diptera ; even the 
mosquito possesses it,’? but he does not 
further describe it, in other diptera than 
Musca. 
The tip of the labrum-epipharynx seems 
to turn upward (fig. 1, lr-e), although 
the opening is upon the ventral surface, 
as may be seen in fig. 6, 6, which repre- 
sents the ventral view of the tip of this 
part. The tip of the labrum-epipharynx 
is comparable to a quill-pen with three 
tips near each other, the middle one of 
these three tips being slightly shorter 
than the other two. The two lateral 
portions of the epipharynx, as seen in 
section, when they near the. tip, lay 
themselves closely upon the sides of the 
tubular portion, passing upward upon it. 
as seen in fig. 5, lr-e; they thus serve to 
strengthen the two outer points of the 
14 Macloskie, G: The proboscis of the house-fly. 
(Amer. naturalist, March 1880, v. 14, p. 153-161, fig. 
I-3.) 
