THE METAMORPHOSIS OF INSECTS. 239 
tightly cemented by the gluey substance. The old clothes 
are always at the other end, so as not to be in the way. 
The new coat which was formed as it entered the pupa 
state is easily torn, and the Moth, moistening the cocoon 
with a fluid from its mouth at the part where it is to es- 
cape, easily forces its way through. The opening from 
which it emerges is very small, and the shape of the an- 
imal before it expands its wings is that of a long bundle. 
412. The thread with which the worm makes its co- 
coon is an unbroken one. It can, therefore, be unwound 
or reeled off, which is done in o taining it for manufac- 
ture. For this purpose the cocoons are exposed to the 
heat of an oven in order to kill the pupz in them, and 
then, by a little soaking in warm water, the glutinous 
matter which unites the silk is so softened that the thread 
can be readily unwound. The length of it varies from six 
hundred to a thousand feet; and as it is double as spun 
out by the insect, its real length is nearly two thousand 
feet. So fine is this double thread, that the silk that 
comes from one cocoon does not weigh above three 
and a half grains, and it requires ten thousand cocoons 
to supply five pounds of silk. The native countries of 
the Silkworm are China and the East Indies; and in an- 
cient times the manufacture of silk was confined to them. 
So scarce was the article in other countries, even as late 
as James I. of England, that this monarch, before his 
accession to the throne, wore on some public occasion a 
borrowed pair of silk stockings. But at the present 
time the culture of the Silkworm and the manufacture 
of silk are so widely diffused, that silk is every where, 
in civilized communities, one of the common articles of 
dress. 
413. When a pupa is to remain out of doors all the 
winter, special pains are taken to guard it against the 
cold. For this purpose great numbers of Insects in the 
autumn dig their way down into the ground, and pass 
their pupa state in an earthy cell below the reach of 
