MAXILLARY PALPI; LABIUM 41 
the stouter maxillary palpi just before passing under the clypeus, and immedi- 
ately afterwards they join the labium, and become imbedded, with the man- 
dibles, in connective tissue. (See fig. 9, ma.) Their continuations in the head 
are two delicate chitin-supports, each of which ends in a strong muscle; this 
muscle, the retractor maxille (fig. 10, rm), passes backward and downward 
through the head, beneath the infracesophageal ganglion, and has its origin in 
the posterior basal part of the head. The maxille probably have no protractor 
muscle, their forward motion being due to the elasticity of the chitin frame-work 
of the head. The shaft of the maxille is very transparent, except near the inner 
side where the chitin-rod runs; here it is brownish and more opaque. Out from 
the above-mentioned chitin-rod extends a very delicate feathering, or corruga- 
tion, of chitin to the edge of the most transparent portion of each maxilla, as 
seen upon the basal portion of fig. 5, mz. The tip of the maxille (fig. 5, mz) 
is very acute, has none of the before-mentioned chitinous corrugations, but, in 
their place, near the outer edge, is a row of papille, which have their tips 
slightly recurved toward the head, and consequently appear serrate. These 
papille are upon the upper surface of the maxille, as can be readily seen, by 
preparing the mouth-parts by lateral pressure, as in fig. 1. 
“The maxillary palpi (figs. 1, 2, and 9, mp) are four-jointed in some species 
of Culex, five-jointed in others. At first sight they appear to be three-jointed, 
but more careful examination serves to show that the apparent basal joint is 
made up of two joints, and oftentimes to reveal a very short, knob-like joint at 
the extremity of what appears to be, at first, the apical joint. At their base the 
maxillary palpi join the maxilla just before the latter pass beneath the clypeus, 
and, with the maxille, join the other mouth-parts, as shown, in section, by fig. 9. 
“The function of the maxille is, probably, to draw the other mouth-parts 
into the skin, when Culez bites, for if one watches the maxillary palpi of Culex, 
while the sete are entering the skin, the sete seem to pierce the skin, and enter 
it with a slow gliding motion, as if drawn from below, instead of pressed from 
above ; meanwhile, if one observes carefully, with a lens, the maxillary palpi can 
be seen to be in an alternating motion, as if the maxille to which they are 
attached, pressed, first one then the other, into the skin, and then pulled the 
other parts after them. The muscles, retractores maxillarum, already described, 
lend weight to this view of the functions of the barbed maxille. 
“The labium (figs. 1, 2, and 3, 1), the largest of the mouth-parts of Culez, 
and the only one of them, helping form the proboscis, which contains muscles, 
forms a sheath opening along the upper side, and receiving in its channel the 
other mouth-parts (excepting the maxillary palpi), as seen in cross-section in 
fig. 8; it tapers from base to tip, is flexible, has a delicately annulated structure, 
and is clothed with hair and scales. At its base it unites with the maxille, man- 
dibles, and hypopharynx, and continues into the under surface of the head. 
Throughout its length it contains, on each side, muscles, which have their origin 
in the base of the head and serve to control the motions of the labium. (See 
figs. 8 and 9, ml.) At the sides of the tip of the labium are attached two lobi- 
form appendages, the labelle, which are seen at Ib in fig. 3 with the true tip of 
the labium proper between them. These terminal lobes are jointed to the 
labium, a little distance behind its tip, as can be seen in fig. 7, which is a cross- 
section of the labium a trifle anterior to the actual centre of motion of these 
joints. The section of that portion of the labium which extends forward to form 
its tip is seen in the middle of the figure, just below the section of the maxille 
(mx). Outside the section of each lobe is seen the section of a portion of the 
exterior edge of the labium itself, which here forms a double socket, or pair of 
acetabula, into which the heads of the two labelle are set. Each of the lobes of 
the labium,—the labella,—is provided with an extensor and flexor muscle (fig. 
7, me, and mf), and is attached to the labium by a true joint. 
