576 Cut PING 
separated from the rest of the skeleton. These sclerites are connected 
ventrally by a hypopharyngeal sclerite. The rest of the skeleton is divided 
into dorsal and ventral lateral plates. Each has a caudal process projecting 
posteriorly. The dorsal and ventral plates are connected with a dorso- 
ventrad piece, making an I-shaped outline (Plate LV,19). At the anterior 
end of the dorsal plate lies the epipharyngeal sclerite. The caudal part 
of the ventral lateral plate is broad but gradually thins away. Near the 
dorsal angular border of this plate an oval opening is often found. 
The pharynx, as in the larva of Musca, has eight grooves separated 
by the bifurcating ribs at its floor. These ribs, differing from those found 
in the Musca larva, are rather Y-shaped, with fine comb structures at 
the tips of the upper processes. This evidently suggests a straining 
function. The loose membrane attached to the layer of cells ccvering 
the lateral plate, found by Hewitt in the Musca larva, is also found here 
(Plate LV, 19). 
The esophagus is uniform in diameter throughout its length. It passes 
through the foramen between the cerebral lobes and the subesophageal 
ganglion, leading posteriorly to the proventriculus (Plate LV, 14), with 
which it communicates by means of the esophageal valve. 
The proventriculus has very thick epithelium and its shape is more or 
less oval. As the posterior esophagus telescopes into the central core 
of the proventriculus, the large, clear cells of the proventriculus surround 
this inserted part. At the anterior part of the proventriculus and at the 
posterior end of the esophagus the epithelial cells are very large. 
The chyle stomach may be divided into two parts. The narrow anterior 
part is the ventriculus, while the broader posterior part is the mid-intestine. 
The convolution of the chyle stomach is very complex. The anterior 
end, where the four caeca arise, is the broadest part in the entire ali- 
mentary canal. The epithelial cells of the ventriculus are large. The 
striated appearance, as in the other dipterous larva, is found on the sides 
of cells facing the lumen. The mid-intestine has a very thin epithelium 
and the wall of this part in the alimentary canal is almost transparent. 
The lumen, of course, is much larger than in the ventriculus (Plate 
LVI, 25). 
The hind intestine begins with a very narrow part, then it broadens, 
but as a whole it is much narrower than the chyle stomach. It curves 
immediately after it commences, at the place where the malpighian tubes 
