The history of silk, cotton, linen, wool, and other fibrous ... - Cd3wd.com

DESCRIPTION OF THE SILK-WORM. 107
Worms newly freed from their exuviae are easily distinguished
from others by the pale color and wrinkled appearance of their
new skin. This latter quality, however, soon disappears,
through the repletion and growth of the insect, which continues
to feed during five days. At this time its length will be in-
when it is attacked by a second sick-
creased to half an inch ;
ness, followed by a second moulting, the manner of performing
which is exactly similar to the former. Its appetite then again
returns, and is indulged during other five days, in the course of
which time its length increases to three quarters of an incli : it
then undergoes its third sickness and moulting. These being
past in all respects like the former, and five more days of feed-
ing having followed, it is seized by its fourth sickness, and casts
its skin for the last time in the caterpillar state. The worm is
now about one and a half or two inches long. This last change
being finished, the worm devours its food most voraciously, and
increases rapidly in size during ten days.
The silk-worm has now attained to its full growth, and is a
slender caterpillar from two and a half to three inches in length
(See Figure 1. Plate III.). The peculiarities of its structure
may be better examined now than in its earlier stages. It can
readily be seen that the worm has twelve membranous rings
round its body, parallel to each other ; and which, answering to
the movements of the animal, mutually contract and elongate.
It has sixteen legs, in pairs : six in front, which are covered
with a sort of shell or scale, and are placed under the three first
rings, and cannot be either sensibly lengthened, or their position
altered. The other ten legs are called holders : these are mem-
branous, flexible, and attached to the body under the rings, be-
ing furnished with little hooks, which assist the insect in
cUmbing. The skull is inclosed in a scaly substance, similar to
the covering of the first six legs. The jaws are indented or
serrated like the teeth of a saw, and their strength is great con-
sidering the size of the insect. Its mouth is peculiar, having a
and the worm is fur-
vertical instead of an horizontal aperture ;
nished with eighteen breathing holes, placed at equal distances
down the body, nine on each side. Each of these holes is sup-
posed to be the termination of a particular organ of respiration.