44 MOSQUITOES OF NORTH AMERICA 
which, in the female, is formed by the labium alone. Whether the joint near the 
middle of the labium of the male Culex is true or false I cannot say, since I 
have never seen it bent by the insect itself ; its appearance is that of a true joint. 
Like the labium of the female, that of the male has two longitudinal main 
tracheal stems (figs. 12-14, tr), and two rows of longitudinal muscles.” 
Kraepelin expressed the opinion that the labrum is not formed by the union 
of two pieces, the labrum and epipharynx, but that it is an evagination of the 
head and in consequence necessarily hollow. “It can therefore, as all body- 
appendages are evaginations and consequently hollow, impossibly be interpreted 
as the fusion of an upper and lower lamina.” 
Becher was of the same opinion and states that the so-called epipharynx of 
the Diptera is never found as a free part; he calls the part the lower lamella of 
the labrum. 
Meinert has traced the course of the salivary duct and found that it differs in 
the two sexes. His interpretation of the hypopharynx does not agree with that of 
Dimmock. In the female Meinert found that the salivary duct penetrates the 
posterior part of the hypopharynx; before entering it forms a large receptacle 
from the upper part of which a strong muscle extends to the under side of the 
pharynx. “In the male the hypopharynx does not protrude but is very short 
and rounded anteriorly and the salivary duct runs through the entire sheath 
[labium] along the under side of its floor until it terminates in the tongue.” 
Wesché considers the hypopharynx of the male as long, like that of the fe- 
male, and the “ tongue” of Meinert, protruding between the labelle, as its apex. 
He speaks of the ciliation of the free apex, which he states to be present in all 
males, as “ a surprising reversion ”; perhaps it can be explained as readily as an 
adaptation to the feeding habits of the male. One gets the impression from 
Wesché’s paper that he believed that the hypopharynx is free in the male 
throughout its entire length ; such does not, however, appear to be the case. He 
figures the abnormal mouthparts of a male Anopheles maculipennis which ap- 
proach those of the female. Not only the mandibles and maxille are present, but 
also a free hypopharynx which extends to the tip of the proboscis. 
The mandibles of Diptera are present only in the females of the blood-sucking 
orthorrhaphous forms. Becher, whose work has been criticized for its inexact- 
ness, states that two parts can usually be clearly distinguished in these organs: 
“a basal piece, which lies in the interior of the head, and the mandible proper, 
which can be moved upon this base by means of a joint.” None of the students 
who have followed exhaustive methods appear to have detected any such joint. 
Becher’s interpretation of the mouthparts is at variance with the commonly 
accepted homologies in various details but his paper is neither clear nor con- 
vincing. Furthermore, he commits the error of basing his views on studies of 
the mouthparts of the higher Diptera and interpreting the lower forms from this 
standpoint ; thus we can, with the more propriety, pass over a detailed considera- 
tion of his work. It may, however, be pointed out in passing, that while Becher 
Tightly, we believe, rejects the idea, held by some of the earlier authors, that the 
maxille and even the mandibles may enter into the composition of the labium 
