THE AMERICAN SILK WORM. 87 
spread over all the inside of the cocoon. The larva con- 
tinues to work for four or five days, hardly taking a few 
minutes of rest, and finally another coating is spun in the 
interior, when the cocoon is all finished and completely 
air tight. The fibre diminishes in thickness as the com- 
pletion of the cocoon advances, so that the last internal 
coating is not half so thick and so strong as the outside 
ones. l 
During the process of spinning, the worm contracts and 
diminishes in size, as the silk reservoirs empty. Six or 
eight days after the beginning of the cocoon, the worm 
casts its last larva-skin, and then appears under a very dif- 
ferent form—a transitory one, which is neither worm nor 
moth; it is the chrysalis or : 
pupa. When the chrysalis 
comes out of the larva skin, 
if observed closely, it will be 
seen that its resemblance to a 
the perfect insect is striking ; Pupa of Tin Piesk a: 
the antennæ, the head, the legs and abdomen resemble 
very much those of the moth. The wings only, are 
very small, but in a few minutes they grow to about half 
the size of the abdomen. The legs of the chrysalis, at- 
least the tarsi, are enclosed in the articulated leg of the 
and third segments, and the antenne are rolled up in the 
lobes of the cranium. When the chrysalis comes out, 
every part is detached and free, and if then put in alcohol 
they will remain so; but when left to its natural course it 
will soon be observed that a general envelope covers the 
whole chrysalis, and that any motion of the legs, wings 
and antennz is impossible, since the insect is contained in 
the hard brownish envelope secreted by its tegument, and 
