A friend of mine put about fifty large caterpillars collected from cabbages
on some bran and a few leaves into a box, and covered it with gauze to
prevent their escape. After a few days we saw, from more than three fourths
of them, about eight or ten little caterpillars of the ichneumon-fly come
out of their backs, and spin each a small cocoon of silk, and in a few days
the large caterpillars died. This small fly it seems lays its egg in the
back of the cabbage caterpillar, which when hatched preys upon the
material, which is produced there for the purpose of making silk for the
future nest of the cabbage caterpillar; of which being deprived, the
creature wanders about till it dies, and thus our gardens are preserved by
the ingenuity of this cruel fly. This curious property of producing a silk
thread, which is common to some sea animals, see Botanic Garden, Part I.
Note XXVII. and is designed for the purpose of their transformation as in
the silk-worm, is used for conveying themselves from higher branches to
lower ones of trees by some caterpillars, and to make themselves temporary
nests or tents, and by the spider for entangling his prey. Nor is it
strange that so much knowledge should be acquired by such small animals;
since there is reason to imagine, that these insects have the sense of
touch, either in their proboscis, or their antennæ, to a great degree of
perfection; and thence may possess, as far as their sphere extends, as
accurate knowledge, and as subtle invention, as the discoverers of human
arts.

XVI. 1. If we were better acquainted with the histories of those insects
that are formed into societies, as the bees, wasps, and ants, I make no
doubt but we should find, that their arts and improvements are not so
similar and uniform as they now appear to us, but that they arose in the
same manner from experience and tradition, as the arts of our own species;
though their reasoning is from fewer ideas, is busied about fewer objects,