662 THE POPULAR SCIENCE MONTHLY. 



born infant ; the caterpillar, when perfectly developed, is 72,000 times 

 heavier than when it first came from the egg. 



In every thing that relates to the body, there is between men and 

 animals more resemblance than is ordinarily believed. We also come 

 from an egg which essentially resembles all others. That this egg 

 may become a man, it must undergo very great changes, many meta- 

 morphoses. But all these changes, all these metamorphoses occur in 

 the bosom of the mother, as they are accomplished within the shell for 

 the chicken. For insects in general, and consequently for the silk-worm, 

 a part of these metamorphoses occur in the open day. Hence they 

 have drawn the attention, excited the curiosity, and provoked for a 

 long time the study of naturalists. Let us say a few words about them. 



Scarcely is the caterpillar born than it begins to eat. It has no 

 time to lose in gaining a volume 72,000 times greater than it had at 

 first ; so it acquits itself conscientiously of its task, and does nothing 

 but eat, digest, and sleep. At the end of some days this devouring 

 appetite ceases ; the little worm becomes almost motionless, hangs 

 itself by the hind-feet, raising and holding a little inclined the ante- 

 rior of its body. 



This repose lasts 24, 36, and even 48 hours, according to the tem- 

 perature ; then the dried-up skin splits open behind the head, and 

 soon along the length of the body. The caterpillar comes out with a 

 new skin, which is formed during this species of sleep. 



This singular crisis, during which the animal changes his skin as 

 we change our shirt, is called moultmg, when it is a question of cater- 

 pillars in general. For the silk-worm, we designate it under the name 

 of sickness. It is, in fact, for the silk-worm, a grave period, during 

 which it often succumbs, if its health is not perfect. 



Fig. 8. Fig. 9. 



Head of Silk-worm during Moulting ; Position of Silk-worm while Moulting. It 



swollen, and skin wrinkled. remains at rest for from 12 lo 24 hours, last- 



ing, but begins to eat an hour after the crisis 

 in which it escapes from the old skin. 



The silk-worms change their skin four times. After the fourth 

 moulting comes a redoubled appetite, which permits them to attain 

 their full size in a few days. Then other phenomena appear. The 

 caterpillar ceases to eat, and empties itself entirely ; it seems uneasy, 

 wanders here and there, and seeks to climb. Warned by these symp- 

 toms, the breeder constructs for it with branches a cradle or bower, into 

 which it mounts. It chooses a convenient place, hangs itself by the hind 

 feet, and soon, through the spinner of which I have spoken (Fig. 2), 



