THE METAMORPHOSIS OP 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 staining it for manufac- 

 ture. For this purpose the cocoons are exposed to the 

 heat of an oven in order to kill the pupaB 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 grams, 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 tunes 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 



