LETTERS ON ENTOMOLOGY. 47 
cannibals, and eat each other. Twenty of this 
fierce race were put into a glass box by Reaumur, 
and regularly fed with oak leaves. It was re- 
marked that their number diminished daily, and 
yet there were no dead bodies ; this excited his 
attention, and he observed that when one met 
another, it seized it with its teeth near the head, 
and quickly inflicted mortal wounds. Wounded 
caterpillars either soon die or become weak, thus 
the conqueror found any easy prey ; and when 
it could not escape quietly, sucked and eat it, 
leaving the skin. The aggressors always ap- 
peared the strongest. Of these twenty cater- 
pillars there only remained one, which was so 
greedy that it would not quit its hold of the last 
victim. 
The most terrible enemy they have is the grub 
of an ichneumon fly, which lives in their insides, 
and is so well concealed that no one would su- 
spect it, as the poor caterpillar looks as well as 
usual, though its internal parts are continually 
being devoured. These grubs are of two sorts — 
those which live in society, and those which live 
alone : they all undergo a metamorphosis. They 
are produced by a beautiful green ichneumon 
fly, which pierces the skin of the caterpillar, and 
deposits its eggs in the hole. In due time the 
