SILK-WORMS. 
3 
4th, On their transition from the state of cater- 
pillar to that of apparent death, or chrysalis. 
5th, On the change of the chrysalis into a per- 
fect animal, or butterfly ; on the laying of the 
impregnated eggs, and on the death of the but- 
terfly. 
6th, On the method adopted by nature to de- 
stroy a great number of them, that they might 
not exceed the limits fixed for them, and on the 
means which man may employ with the same ob- 
ject in view.. 
ls£. On the General and External Characters of 
Caterpillars . 
Caterpillars have, as I have observed, a long 
body, more or less cylindrical, which is formed in 
its length of twelve membranous parallel rings, 
which, in the movements of the animal, mutually 
contract and elongate. They have uniformly a 
scaly head, of a substance similar to horn, pro- 
vided with two very strong jaws, formed like a 
saw, which are moved horizontally, and not from 
above downwards, as among animals with red 
blood. Under the jaws is placed the contrivance 
by which each caterpillar deposits the silky sub- 
stance. They have never fewer than eight feet, and 
never more than sixteen ; the six first, formed of 
a scaly substance similar to that of the head, are 
fixed under the three first rings, and can neither 
B 2 
