568 Cuin PING 
above. The second, or first thoracic, segment is partly retracted and 
a pair of sense papillae are visible both laterally and ventrally. Owing 
to the retraction of these two segments, there results an oval opening or 
invagination, bordered by the fold of the integument of the first thoracic 
segment, situated cephalo-ventrad at the anterior end of the larva. In 
the specimens fixed in Bouin’s or Gilson’s solutions, the wrinkles in the 
integument are flattened out, and the first two segments are stretched 
and distended, so that they can be easily examined; but the segments 
throughout the whole body are not very distinct externally. 
The shape of the body is more or less cylindrical. The body tapers 
off gradually from the third segment toward the anterior end, while the 
diameter increases from the twelfth segment toward the posterior end; 
but for the most part the diameter of the abdominal segments is fairly 
uniform. The caudal process is circular in cross section and terminates 
with a more or less truncate end, where two cylindrical branches arise. 
Through these branches the main trunks of the tracheal system come to 
the exterior. The average length of the full-grown larva (Plate LIV, 2), 
including the caudal process with its branches, is 12 millimeters. 
The integument.—In the young larva the integument is grayish in 
color, and is thin and more or less transparent, so that some of the internal 
organs can be seen through the skin. The body is more or less hairy. 
In the mature larva the hairs on the dorsum are more pronounced than 
those on other parts of the body. On the dorsum are seven somewhat 
V-shaped blotches, the hairs of which are modified into flat scales. The 
prothoracic segment is covered with short and blunt bristles. 
In cross section the cuticular integument is composed of two layers. 
The outer layer is thin and slightly chitinous, bearing the chitinous hairs, 
while the inner layer is very thick and homogeneous in structure. Under- 
neath the two layers is a thin layer of hypodermis. The writer has never 
been able to see the hexagonal cells of the hypodermis as mentioned by 
Tragardh (1903). However, the large oval nuclei of these cells are very 
conspicuous. 
The appendages.— The very short antennae, each consisting of two 
joints, are above the prominent oval lobes and are scarcely visible at all 
when the head is retracted. A pair of chitinous prothoracic stigmas, 
each consisting of four digits, are borne one on each side in the second 
segment. The stigmas are ordinarily visible, but sometimes, by the 
