THOMPSON: ANATOMY OF MOSQUITO. 
161 
cles ” (Christophers, : 01 ), “muscles of the pumping organ” (Annett 
and Dutton, : 01 ), “dilator muscles ” (Giles, : 02 ). Dimmock figures 
and refers to the lateral and dorsal dilator muscles but does not 
name them. In the anterior, preneural, part of the pump the ven¬ 
tral uniting strip between the ventro-lateral plates — always broader 
than the two dorso-lateral strips — becomes wide and flat, so that 
the antlia in this region is four-sided (pi. 13, fig. 8). This must 
diminish the movement of the walls and dorsal plate. At this 
point the dorsal plate receives a vestigial dorsal dilator muscle (ant 
dll'). In Anopheles, where the activity of this part of the pump is 
less diminished, two dilator muscles reach the dorsal plate, “anterior 
dorsal dilators” (Nuttall and Shipley, : 01 -: 03 ). 
The epithelium of the proboscis canal, pharynx, and antlia is in¬ 
conspicuous. It is flattened over the proboscis canal and antlia 
more than over the pharynx. The intrinsic muscle coats are not 
evident, except over the hinder end of the antlia where a powerful 
sphincter muscle is developed (pi. 12, fig. 2, sph m ). 
The male of Culex has a more attenuated antlia with a relatively 
smaller bulbous portion than the female. The total capacity is less 
than that of the female’s antlia even when the latter insect is repre¬ 
sented by a smaller specimen. Computed by Cote’s rule, the larg¬ 
est male antlia found in C. stimidans had a capacity of approxi¬ 
mately 0.0008 cu. mm. The smallest female antlia of the same 
species measured 0.002 cu. mm., and the largest 0.004 cu. mm. 
The time taken by a mosquito of this species to draw up its meal of 
blood depends on the nature of the spot pierced, averaging accord¬ 
ing to my observations about one minute for a light and nearly half 
as long again for a heavy meal. But under especially favorable 
conditions the lesser meal can be taken in 50 seconds, the greater in 
65 seconds. Since a heavy meal consists of nearly 4.5 cu. mm. of 
blood, a very rapid action of the antlia would seem to be required, 
especially if this pump empties itself at each stroke. More probably, 
however, it acts to maintain a continuous rather than, an intermit¬ 
tent flow. 
The antlia of Anopheles corresponds closely to that of Culex in 
structure. The most important difference is the greater functional 
activity of the anterior or preneural part as a pumping organ with 
an accompanying development of the anterior dorsal dilator mus¬ 
cles. As a result, the antlia of Anopheles is more uniformly cylin- 
