LETTERS ON ENTOMOLOGY. 
41 
these difficult and dangerous manoeuvres, it has 
still to get rid of the old skin, which it will by no 
means suffer to remain so near, and the means 
it uses are singular. It seizes it with part of the 
body, which is beyond the hooks, and then gives 
itself a shake, which throws it violently from side 
to side. It thus pulls at the skin, and the hooks 
on the feet break or come out of the silk, being 
farther from the centre of the motion than its 
own hooks. If the skin does not fall after this, 
the chrysalis rests a little, and turns in the same 
manner in a contrary direction • ^4-^ " 
sometimes oungect to repeat tour or five times. 
After all this trouble and pains it resigns itself to 
repose for more than twenty days, and then comes 
forth a butterfly*. 
Caterpillars have many different modes of de- 
fence against their assailants ; some curl them- 
selves round as if dead, some walk or rather run 
away with amazing swiftness : that of the vine 
is remarkable in this respect. Others more 
courageously defend themselves by fixing half 
their bodies, and moving the other half in every 
direction, as if to seize the enemy. Others have 
* The caterpillar of the P. Io, or peacock butterfly, 
changes in this manner, and comes out in eleven or twelve 
days. 
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