INSECT SIPPERS AND GNA WERS. 245 
It is the caterpillars of moths, too, which spin 
those silken cocoons which hang from tree or bush, 
or under walls and palings ; homes so delicate, and 
yet so dry and snug, that the tender pupa lying 
freely inside them is like a child in its warm bed at 
night. Any one who has kept silkworms will 
know how cleverly the caterpillar, bending its head 
back towards its tail so that its feet are outside, 
begins its outer egg-shaped layer of silk by moving 
its head to and fro in some nook or corner, and 
leaving a bed of fluff within which it spins the coil 
of finer silk. You may watch the cocoon growing 
for a time as the caterpillar's head moves round 
and round in an oval form, leaving its silken trail 
behind it. But gradually the meshes grow finer and 
finer, and you can no longer see through them, while 
still the industrious creature goes on till its head has 
been round the oval at least three hundred thousand 
times, and it has made a stout cocoon. 
Once safe inside its silken house, it pushes off its 
caterpillar skin and remains a protected pupa for a 
fortnight or more. Then, if you have not already 
robbed it of its silk, the moth, after it has crept out 
of the pupa skin, must work its way through the 
cocoon. This it does by giving out a liquid which 
is contained in a little bladder in its head, and 
soaking the silken wall so as to separate the threads 
and make a path for itself to the outer air. But 
curiously enough it will not attempt to fly far, for the 
silkworm moth, belonging as it does to a genus 
already feeble in flight, and having besides been 
kept in confinement for generation after generation, 
makes scarcely any use of its wings. 
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