SILK-WORMS. 
15 
There is a great difference between the silk 
drawn by the silk-worm and that of other cater- 
pillars. With tepid or hot water, the gummy 
substance, which unites the threads of the cocoons 
of the silk-worm, may be dissolved, which ren- 
ders the silk easy to wind ; whilst the threads of 
the silk produced by other caterpillars, adhere 
so closely together, there are no means of loosen- 
ing and separating them ; the only manner of 
making any use of it, would be to tear or cut the 
cocoons, and then card them, as is done with the 
floss or coarse interior part of the cocoon of the 
silk-worm ; in this way, the silk of many cater- 
pillars might become of some advantage in do- 
mestic economy, as the cocoons of common cater- 
pillars are to be found in all places. 
5th. Transition of the Chrysalis to the state of 
perfect Animal or Moth. — Production of the 
impregnated Eggs. — Death of the Moth. 
The caterpillar is subject in the course of its 
existence to three changes of organization. 
The first change takes place when the embryo 
passes to the state of caterpillar, during which 
passage, those moultings or castings of the skin 
occur, which I have before noted, (Chap. I. § 11.) 
The second change is the transition of the ca- 
terpillar to the state of chrysalis, or aurelia, in 
the cocoon it has formed for itself, (Chap. I. § 4.) 
