THE ESCAPE OF THE MOTH. 
117 
The caterpillar does not spin it round and 
round its body as is generally done, but half 
finishes it before getting in. The two pieces are 
glued together quite fast except at one end, and 
here, though it seems as strong as the rest, they 
are merely made to meet, and held in their place 
by a few threads, that are fastened down on the 
inside. The threads are so slight that the moth 
can break them, and push her way out, between 
the two pieces. But they instantly close behind 
her, and the boat looks just as, it did before. 
But the most curious kind of cocoon that 
opens and shuts in this manner, is that made by 
the caterpillar of the emperor moth. It is very 
common; and you may find it, at the right season, 
on the willow or the pear tree. It is made of 
rough-looking silk, and is shaped like a flask, with 
a hole at the narrow end. But to prevent any 
insect getting in, the caterpillar gums together a 
number of threads of silk, and sets them like 
sharp spikes round the inside of the hole. The 
spikes are as elastic as whalebone, and can easily 
be pushed open from within; but if an insect 
were to try to force an entrance, it would be re¬ 
ceived on the sharp points like so many wires. 
In fact, the caterpillar has made the cocoon 
after the fashion of a trap; only in this case the 
moth within the trap can get out, and nothing 
