Silk-Worm. 337 



takes up the thirteenth and fourteenth days, and the last 

 occurs on the twenty-second and twenty-third days. The 

 fifth age, in such cases, lasts ten days, at the end of which, 

 or thirty-two days after hatching, the caterpillars attain 

 their full growth, and ought to be three inches in length ; 

 but if they have not been properly fed, they will not be so 

 long. 



With the age of the caterpillar, its appetite increases, 

 and is at its maximum after the fourth moulting, when it 

 also attains its greatest size. The silk gum is then elabo- 

 rated in the reservoirs, while the caterpillar ceases to eat, and 

 soon diminishes again in size and weight. This usually 

 requires a period of nine or ten days, commencing from the 

 fourth moulting, after which it begins to spin its shroud of 

 silk. In this operation it proceeds with the greatest caution, 

 looking carefully for a spot in which it may be most secure 

 from interruption. 



' We usually," says the Abbe de la Pluche, " give it some 

 little stalks of broom, heath, or a piece of paper rolled up, 

 into which it retires, and begins to move its head to different 

 places, in order to fasten its thread on every side. All this 

 work, though it looks to a bystander like confusion, is not 

 without design. The caterpillar neither arranges its threads 

 nor disposes one over another, but contents itself with dis- 

 tending a sort of cotton or floss to keep off the rain ; for Nature 

 having ordained silk-worms to work under trees, they never 

 change their method even when they are reared in our houses. 



" When my curiosity led me to know how they spun and 

 placed their beautiful silk, I took one of them, and frequently 

 removed the floss with which it first attempted to make 

 itself a covering ; and as by this means I weakened it exceed- 

 ingly, when it at last became tired of beginning anew, it 

 fastened its threads on the first th'ing it encountered, and 

 began to spin very regularly in my presence, bendiog its 

 head up and down, and crossing to every side. It soon 

 confined its movements to a very contracted space, and, by 

 degrees, entirely surrounded itself with silk; and the re- 

 mainder of its operations became invisible, though these may 



