110 GROWTH OF THE SILKWORM. 



and twelve or thirteen hundred pounds during the fifth period. 

 It is on the sixth day of the last age, that the greatest voracity 

 shows itself. The worms then devour two or three hundred 

 pounds of leaves, and when eating make a noise which resem- 

 bles that of a heavy shower. On the tenth day they cease 

 eating, and prepare themselves to undergo their first metamor- 

 phosis. We then see them endeavouring to climb upon the 

 branches of small bundles of twigs, which have been carefully 

 placed above the frames on which they have until then remained. 

 Their body becomes soft, and a thread of silk comes out of their 

 mouth, which they draw after them. They very soon fix them- 

 selves, and throw around them a multitude of threads of extreme 

 fineness ; and, suspended in the middle of this net- work, spin 

 their Cocoon, which they form by continually turning themselves 

 round in different directions thus twisting round their body the 

 thread which comes out from the spinneret, with which the lip 

 is perforated. The silk, thus formed, is produced in glands, 

 which have much ^analogy with the salivary glands of other 

 animals ; and the matter of which it is composed is soft and 

 glutinous at the time of its first appearance, but soon becomes 

 hardened by the air. The result of the different twistings of 

 this single thread, is to cause the different threads to adhere 

 together, and to form an envelope, whose tissue is firm and shape 

 oval. The colour of the silk varies; sometimes it is yellow, 

 sometimes of a brilliant white, according to the variety of the 

 worm which has produced it ; and the length of each thread 

 often exceeds 1100 feet, but varies much, as does also the weight 

 of the cocoons. The worms proceeding from an ounce of eggs 

 may produce as much as 130 Ibs. of silk ; but such an amount is 

 rare ; and from 70 to 80 Ibs. is the usual product. 



630. In general, three days and a half or four days are suffi- 

 cient for the larva to finish its Cocoon ; and if we then open 

 this envelope, we see that the animal no longer presents the same 

 appearance as before its seclusion. It has become of a brownish 

 colour, its skin resembles old leather, and its shape is oval, a 

 little pointed at its posterior extremity. We no longer distin- 

 guish a head or jaws ; but the posterior extremity is formed by 



