PST CRE. 2393 
The unsettled state of our knowledge 
of the anatomy of the mouth-parts of 
Culex, as can be seen by the preceding 
notes, led me to select this genus of di- 
ptera for careful study, with the results 
noted in the following pages. 
IN THE FEMALE. 
The mouth-parts which form the pro- 
boscis of the female Culev, as I have 
found them by study of C. rufus, C. cili- 
atus and C. pipiens, consist of a labrum 
(pl. 1, fig. 1, 7), an epipharynx (e), a 
hypopharynx (1), two mandibles (m), 
and two maxillae (ma), all sheathed, 
when in repose, in the labium (/), which 
receives them into a groove on its upper 
side. Each maxilla has a maxillary pal- 
pus (mp), which lies outside the labium ; 
the latter has no palpi. The labium and 
maxillary palpi are covered with hair and 
scales ; the other mouth-parts are naked, 
light brown, setiform and transparent ; 
they all originate at the anterior basal 
portion of the head, and are, with the 
exception of the maxillary palpi, of about 
equal length, that is, about three to four 
times the length of the head. The max- 
illary palpi, in the females of Culex 
proper, are about the length of the head. 
The scaleless mouth-parts are not jointed, 
and are the ones which penetrate the skin 
in biting. The labrum and epipharynx 
are united in their whole length, forming 
a piece which is shown in section in fig. 
6, d. The other mouth-parts are free to 
the base. A pumping organ, trianguloid 
‘in cross-section (fig. 10, 6), is formed by 
a dilation of the oesophagus behind the 
oesophageal nerve-ring. Each of the 
above-mentioned parts will be described 
more in detail later. In comparative size 
and strength the mouth-parts would be 
arranged as follows, the largest and 
stoutest first: labium, labrum-epiphar- 
ynx (the name by which I designate 
this compound piece in diptera), hypo- 
pharynx, maxillae and mandibles. 
The general arrangement of the mouth- 
parts, relative to each other, is shown 
‘best in fig. 8, which is a figure of a 
cross-section through the middle of the 
proboscis of a female Culex rufus, while 
in repose, with the setae sheathed in the 
The labium (/), clothed on the 
outer side with its scales and hairs, is 
wrapped nearly around the other mouth- 
parts. In it lie the two maxillae (mz), 
partly enclosing the parts above them, 
and thus helping to bind the parts to- 
gether; above the maxillae are the two 
mandibles (m), and immediately above 
the mandibles, in the median line, is the 
hypopharynx (/), with a thickened mid- 
dle portion. Resting on the hypo- 
pharynx is the labrum-epipharynx ; the 
epipharynx (¢). is omega-form in sec- 
tion, and above it, delicately attached, is 
the labrum (/7). The changes in relative 
position which the mouth-parts of Culex 
undergo as they approach the head can 
be best described in the subsequent de- 
scription, in detail, of each separate 
labium. 
part. 
The labrum-epipharynx (figs. 1, 5, 6, 
7-8; lr and e) of Culex consists of the 
thin labrum resting upon and fastened to 
the epipharynx ; it tapers gradually from 
base to apex. The epipharynx is omega- 
form in cross-section, being a channel 
