98 Insect Life : Its Why and Wherefore 
find their dwelling-place too cramped. 
They then proceed to split their covering 
down the middle and interpose a new piece 
according to their needs, sometimes 
adding a piece at the anterior end, if it is 
length rather than breadth which they 
require. This addition to the size of the 
sheath can be seen quite readily, without 
the use of a magnifying glass, by simply 
transferring the grub from material of one 
colour to material of another, when the 
additions will be easily observable from the 
difference in colour. The thickness of 
covering which the grubs make use of 
varies also in thickness according to the 
material from which he builds his woolly 
house. The grubs of the wax moth, 
whose habits are very much the same, 
will sometimes cover themselves in in 
very much the same manner, while nothing 
is visible from which they can weave a 
covering, while traversing a sheet of wax. 
The wool, in addition to supplying a 
covering to the grub, also furnishes it with 
food at the same time. When the larva 
has attained its full size its appetite begins 
to fail and all food is gradually abandoned, 
