13 
ete.; but the same relative proportion of time between molts usually 
holds true. 
The color of the newly-hatched worm is black or dark gray, and it is 
covered with long, stiff hairs, which, upon close examination, will be 
found to spring from pale colored tubercles. Different shades of dark 
gray will, however, be found among worms hatching from the same 
batch of eggs. After the first molt, and as the worm increases in size, 
these hairs and tubercles become less noticeable, and the worm gradu- 
ally gets lighter and lighter, until, in the last stage, it is of a cream- 
white color. When full grown it presents the appearance of Fig. 1. 
It never becomes entirely smooth, however, as there are short hairs 
along the sides, and very minute ones, not noticeable with the unaided 
eye, all over the body. 
The preparation for each molt requires from two to three days of 
fasting and rest, during which time the worm attaches itself firmly 
by the abdominal prolegs (the 8 non-articulated legs under the 6th, 
7th, 8th, and 9th segments of the body, called prolegs in contradistine- 
tion to the 6 articuiated true legs under the Ist, 2d, and 3d segments), 
and holds up the forepart of the body, and sometimes the tail. In front 
of the first joint a dark, triangular spot is at this time noticeable, indi- 
cating the growth of the new head; and when the term of “sickness” 
is over, the worm casts its old integument, rests a short time to recover 
strength, and then, freshened, supple, and hungry, goes to work feeding 
voraciously to compensate for lost time. This so-called “sickness” 
which preceded the molt was, inits turn, preceded by a most voracious 
appetite, which served to stretch the skin. In the operation of molting 
the new head is first disengaged from the old skin, which is then grada- 
ally worked back from segment to segment until entirely cast off. Ifthe 
worm is feeble or has met with apy misfortune, the shriveled skin may 
remain on the end of the body, being held by the anal horn; in which 
ease the individual usually perishes in the course of time. It has been 
usually estimated that the worm in its growth consumes its own weight 
of leaves every day it feeds; but this is only an approximation. Yet 
it is certain that during the last few days before commencing to spin it 
consumes more than during the whole of its previous worm existence. 
it is a curious fact, first noted by Quatrefages, that the color of the ab- 
dominal prolegs at this time corresponds with the color of the silk 
which will form the cocoons. 
Having attained full growth, the worm is ready tospinup. It shrinks 
somewhat in size, voids most of the excrement remaining in the aliment- 
ary canal; acquires a clear, translucent, often pinkish or amber-colored 
hue; becomes restless, ceases to feed, and throws out silken threads. 
The silk is elaborated in a fluid condition in two long, slender, convo- 
luted vessels, one upon cach side of the alimentary canal. As these 
vessels approach the head they become less convoluted and more slen- 
der, and finally unite within the spinneret, from which the silk issues in 
