PSS CHE. 200 
tip of the epipharynx, while the labrum 
continues to a sharp point at the tip, 
and, united with the upper surface of the 
epipharynx tube, forms the middle point 
of the tip. The channel, or slit, along 
the under side of the epipharynx, wideus 
toward the tip (fig. 6, 6), leaving thus 
an opening for the passage of fluids into 
the tube of the epipharynx. 
The labrum itself is a thin lanceolate 
lamella of chitin, concave along the un- 
der side from the basal portion to the 
tip, and its concavity rests upon and fits 
to the convexity of the tubular part of 
the epipharynx, to which it is so lightly 
attached that they readily separate by 
application of caustic potash. The outer 
edges of the labrum roll slightly inward 
toward the epipharynx along most of its 
length. (See fig. 6, d.) At its base the 
labrum sends a chitinous support beneath 
the clypeus, where it separates more 
from the epipharynx and has its own 
muscles, indicating that the labrum has 
a degree of motion independent of the 
epipharynx, a motion allowed, perhaps, 
by the elasticity of the connection be- 
tween the labrum and epipharynx. The 
muscles of the labrum (fig. 9, pm’) are 
inserted upon the upper side of its base 
and have their origin on the inner surface 
of the roof of the clypeus. These mus- 
cles are, at least in the females of Culex 
rufus, divided into three portions in their 
upper part, as shown in fig. 9. 
The hypopharynx of the female of 
Cules is a linear, lanceolate, transparent 
lamella of chitin, with a longitudinal rod 
through the middle, the nature of which 
will be discussed later. At its base the 
hypopharynx forms the continuation of 
the under wall of the pharynx. (See 
fig. 11, 4.) The hypopharynx is closely 
pressed the side of the 
epipharynx, completing the tube nearly 
formed by the epipharynx. No muscles 
have their insertion on the base of the 
hypopharynx. Its tip is simply lanceo- 
late (fig. 5, h). In Oulex pipiens and 
C. rufus nothing further is visible (with 
a magnifying power of five hundred 
diameters), in sections of the thicker 
middle portion of the hypopharynx, than 
a simple rod of chitin ; but, in C. ciliatus, 
a North American species of which the 
mouth-parts are larger, this rod appeared 
to be tubular. Is it a rod or is it a tube? 
Menzbier” writes (p. 25) that in di- 
ptera ‘* neither the labrum nor the hypo- 
pharynx possesses a completed tube, but 
only a channel” which leads into the 
salivary duct. That Menzbier is incor- 
rect in affirming that the hypopharynx 
has no complete tube I have clearly 
proved in my observations on Bombylius 
and Hristalis; but the question still re- 
mains unsettled whether Culex has any 
passage, either tube or groove, through 
the hypopharynx. Réaumur® (tome 4, 
part 2, p. 896) discusses the probability 
of a poisonous fluid being secreted by 
Culex, to cause the blood to flow more 
readily when it bites, and since his time 
writers have, on the one hand, accepted 
this statement, without proving the 
presence of such a fluid or of the glands 
to secrete it, or they have, on the other 
hand, denied the existence of such a 
upon under 
15 Menzbier, M. A. Ueber das Kopfskelet und 
die Mundwerkzeuge der Zweifliigler. (Bull. Soc, 
impér. natur. de Moscou, 1880, t. 55, no. 1, p. 8-71, 
tab. 2-3.) 
