APPENDICES. 269 



appearance of health and vigour, feeding with recruited 

 appetite upon its leafy banquet. 



Every fifth day it is attacked with sickness, and under- 

 goes four successive moultings ; at the end of its fourth 

 sickness, it casts, its skin for the last time in the cater- 

 pillar state. The worm is now about one and a half or 

 two inches long. This last change completed, the silk- 

 worm devours its food most voraciously, and increases 

 rapidly in size during ten days. The silkworm has now 

 attained to its full growth, and is a slender caterpillar from 

 two and a half to three inches in length. 



At the period above mentioned, the desire of the worm 

 for food begins to abate. The first symptom of this is 

 the appearance of the leaves nibbled into minute portions 

 and wasted. 



The substance of which the silk is composed is secreted 

 in the form of a fine yellow transparent gum in two 

 separate vessels of slender dimensions, which are wound, 

 as it were, on two spindles in the stomach. If unfolded, 

 these vessels would be about ten inches in length. 



When the worm has fixed upon some angle, or hollow 

 place, whose dimensions agree with the size of its intended 

 silken ball or cocoon, it begins its labour by spinning thin 

 and irregular threads, which are intended to support its 

 future dwelling. During the first day, the insect forms 

 upon these a loose structure of an oval shape, which is 

 called floss-silk, and within which covering, in the three 

 following days, it forms the firm and consistent yellow 

 ball. At the end of the third or fourth day, the worm 

 will have completed its task, and formed its cocoon. 

 When the insect has finished its labour of spinning, it 

 smears the entire internal surface of the cocoon with a 



