240 
INSECTS. 
causes it to place the egg in a situation, where the 
young will find its proper sustenance after it bursts 
from its confinement ! The motions of these dimi- 
nutive creatures may appear to a casual observer to 
be the effect of accident ; but an attention to the 
following facts will convince him that they all tend 
to a certain point. In China, where the silk-worm 
feeds at large in the fields, her eggs are only to be 
found on the mulberry-tree. We never find upon 
the cabbage any eggs of that caterpillar who eats 
the willow, nor see upon a willow the eggs of any 
caterpillar who feeds upon cabbage. But, what is 
still more wonderful, neither the mulberry-tree, the 
willow, nor the cabbage, afford the parent moths 
or butterflies the smallest sustenance : they cannot 
taste their leaves, and yet they are directed by an 
unerring instinct to deposit their eggs upon those 
plants which are appointed for their food in the 
caterpillar state. The little moth, which does so 
much mischief to our curtains, woollen stuffs, and 
paper, is never to be found in a plant. Nor are the 
eo’os of the flesh-fly to be found in any but animal 
substances. Thus is an invariable rule established, 
which is continued from one generation to another 
without the slightest deviation. 
We shall conclude the subject of nidification with 
the following curious instance as related by an in- 
genious naturalist to the late Mr. Adams : “ As I 
was observing one day some caterpillars which were 
feeding voluptuously on a cabbage leaf, my atten- 
tion was attracted towards a part of the piant, about 
