THOMPSON: ANATOMY OF MOSQUITO. 
157 
occupied in the larva by an epipharynx-like structure. Meinert 
('81) figures for Culex muscles joining the alae of the clypeus to 
the roof of the box. I have not been able to find these in three 
species of Culex at my disposal, and they are not present in Anoph¬ 
eles pnnctipennis. 
The pharynx extends from the union of the mouthparts with the 
head to the anterior end of the esophageal antlia. It is developed 
as a pumping organ and the character of its walls and the form of 
its cross section vary in different levels. At first, in the region of 
the anterior hard palate, the floor and walls have a thin intima 
throughout and this steadily involves more and more of the roof of 
the canal as the anterior hard palate narrows. At the same time 
the floor of the pharynx becomes curved, so that by the time the 
trowel-shaped hard palate has vanished, the pharynx consists of a 
curved ventro-lateral plate and a flattened dorsal plate, the two 
meeting in high dorso-lateral angles (pi. 13, fig. 6). The section 
of the tube is either crescentic or that of an inverted arch, accord¬ 
ing to the position of the dorsal plate as it curves down into the 
lumen or is drawn upward by muscular action. For a space after 
the hard palate vanishes, both walls and roof remain thin. Then 
the dorsal plate becomes uniformly thicker. Finally, thinning 
again, it forms the pharyngeo-esophageal valve at the entrance to 
the antlia. Hence the dorsal plate or roof of the pharynx is dif¬ 
ferentiated into four regions : an area of thin chitin with a median 
tongue of thicker chitin, anterior hard palate; a region with uni¬ 
formly thin chitinous intima, soft palate ; a region with uniformly 
denser intima, posterior hard palate; and a narrow area of thin 
chitin forming a valve. The valve and posterior hard palate regions 
are derived from the “ pharynx ” of the larva. The remainder of 
the pharynx and the proximal part of the proboscis canal are formed 
from the “buccal cavity” of this earlier stage. 
The chitinous intima of the floor and side wall of the pharynx is 
uniformly thin except in the region of the posterior hard palate. 
Here, beginning first along the border of the dorso-lateral angles, 
an area of thicker chitin forms on either hand and widens to involve 
all the wall of the canal for a space. Then narrowing again, these 
areas terminate with stout spurs which project past the anterior end 
of the antlia. At the point where they are most extensive, they 
meet across the floor of the pharynx and in the female insect a 
