BR 
are obscured by the dark color of the insect’s back. Occasionally too 
large a fragment to be swallowed with ease clogs the mouth. Some- 
times it enters the mouth and sticks. In such cases the head of the 
larva revolves with ightning-like rapidity and the fragment is nearly 
always disgorged, although sometimes it is swallowed with an evident 
effort. Since the Anopheles larva feeds only upon these light floating 
particles, its specific gravity is nearly that of the water itself and it 
supports this horizontal position just beneath the surface film with 
comparative ease, and in fact without effort, the tension of the surface 
film itself being 
hardly needed _ to 
holdit. It requires 
an effort in fact for 
the Anopheles larva 
to descend (which it 
apparently never 
does up to the period 
of the final larval 
stage, except when 
alarmed), while it 
requires an effort 
for the Culex larva 
to ascend. 
Structurally the 
differences between 
the half-grown 
larve of Culex and 
Anopheles are well 
shown at figs. 13, 14, 
and 15. The great 
size of the head of 
Culex, as contrasted 
with the small head 
of Anopheles is a 
Fig. 14.—Figure at top, half grown larva of Anopheles in feeding posi- most striking differ- 
tion, just beneath surface film. Figure at bottom, half grown larva enee., Tt h e verv 
of Culex in breathing position—greatly enlarged (original). 
long respiratory 
siphon (as Miall calls it) of Culex contrasts markedly with the short 
one of Anopheles. The arrangement of the hairs is entirely different, 
the branching of the hairs of Anopheles, as contrasted with the simple 
hairs of Culex and the little paired star-shaped (apparently branchial) 
tufts on the dorsum of Anopheles are entirely absent with Culex. The 
flaps at the tail end of the body are similar in number, but are held in 
a somewhat different position. 
