186 
LETTEES FROM ALABAMA. 
strong girdle of silk, whick, passing round the 
body near the head, binds them generally in a 
horizontal position, and allows them little scope to 
swing about. It is a remarkable fact, that the 
Butterflies which are evolved from the former 
position, have the first pair of feet so short as to 
be useless as instruments of locomotion, while those 
using the latter mode, have these feet resembling 
the middle and hindmost pairs in form and office. 
This association of characters is invariable ; yet we 
cannot perceive the most distant connexion between 
the presence of a girdle in the pupa, and the de- 
velopment of the feet in the imago. 
But I was going to advert to the change of form, 
which takes place in the transition from the cater- 
pillar to the chrysalis state. Those persons who are 
aware of the fact that such a change occurs, but have 
never observed the process, are apt to imagine that 
the chrysalis comes forth in the form in which they 
see it, all hard and horny from the bursting skin 
of the caterpillar, as the armed Minerva from the 
head of Jupiter. But in truth, the change of 
general form is gradual ; beginning before the dis- 
ruption of the skin, and mainly going on after that 
skin has been thrown off. The former part of the 
alteration consists in a gradual obliteration of the 
annulose divisions, a rounding and shortening of 
the body and a perceptible approximation to the 
form of the matured pupa, especially in the Moth 
tribes. But the change of form which the evolved 
pupa undergoes is most conspicuous in the sus- 
pended butterflies ; and I have never seen it more 
remarkable than in this of the Archippus, although 
I have observed the metamorphosis of many spe- 
cies ; and I may here remark, by the way, that 
