LETTERS ON ENTOMOLOGY. 37 
twenty thousand convex lenses, each supposed 
to be a distinct and effective eye. I do not mean 
that you should think this change a transforma- 
tion. It is in fact nothing but a series of de- 
velopments, for every different skin and future 
form of the insect are enclosed in the caterpillar 
who throws them off as the parts expand. This 
may be perceived by dissection; the wings, 
rolled up into a sort of cord, are between the 
first and second segment of the caterpillar ; the 
antennae (or horns) and trunk are coiled up in 
front of the head, and the legs are sheathed in 
those of the caterpillar. 
Some caterpillars pass the winter in their own 
form ; they either make or find retreats, where 
they remain in a torpid state. Some bury them- 
selves at a considerable depth, and others re- 
main in plants and trees; these generally as- 
semble in numbers under a silken covering. 
There are even some kinds of butterflies which 
live through the winter in a torpid state, from 
which they may be roused by heat. To enume- 
rate all the different kinds would be impossible, 
therefore we must content ourselves with some 
of the most curious. The green and brown cab- 
bage caterpillar feeds only at night, and lives 
underground in the day, though it is sometimes 
