INTRODUCTION. 
97 
menstruum acting on the gum which holds the fibres 
of the silk together, and the animal is able to force 
itself through wdthout haring recourse to any other 
means. It is foimd that the cocoons, from which 
the silk-worm moth has emerged, can occasionally 
be unwound in an unbroken thread, hut in far the 
greater number of instances this is impossible. 
When the caterpillar provides for the egress of the 
moth, it generally does so by making a circular 
incision near the one end, leaving only a small 
portion entire to act as a hinge, and this the moth 
easily pushes oufrvards when it desires to escape. 
But sometimes a much more elaborate contrivance 
is resorted to, of which a curious example is afforded 
by the flask-shaped cocoon of the Emperor -moth. 
This has frequently been so well described, that we 
cannot expect to make it better understood than by 
using the words of a previous witer. “ If you examine 
one of these cocoons, which are common enough in 
some places on the pear tree or the willow*, you 
will perceive that it is generally of a solid tissue of 
hiyers of sillc almost of the texture of parchment ; 
but at the narrow end, or that which may be com- 
pared to the neck of the flask, that it is composed 
of a series of loosely-attached longitudinal threads, 
converging, like so many bristles, to a blunt point, 
in the middle of which is a circular opening. It is 
through this opening that the moth escapes. The 
silk of its cocoon is of so strong a texture and so 
* In Scotland they are most frequently found on heaths 
and moor-land, the Iwa subsisting on the heather. 
