234 
TRANSFORMATIONS OF INSECTS. 
and others of the same form are built close together on a horizontal 
floor, and they are all closed at their summits. The cells of many 
wasps’ nests are always cylindrical in shape, but usually they are 
hexagonal in outline. When a round cell is in contact with six 
other cellules which surround it, the walls flatten regularly on 
account of the equal pressure of the surrounding structures, and a 
geometrical shape is perfected. The result is that the wall of one 
cell becomes really a portion or a layer of a partition which is 
common to two cells, and very soon the double wall is no longer 
seen to exist, for it is not wanted. By building hexagonal cells 
there is a great economy of materials, and this is a very important 
matter when the substances of which some very large nests are 
composed are scarce. 
Everybody respects the wasp, and is aware that the mothers 
and workers are armed with a very strong sting. The larvae 
are feeble creatures ; nevertheless, the head of the wasp larva is 
stronger and larger than that of the other Hymenoptera ; even 
their mouth-pieces are stouter, and this enables them to receive 
bits of fruit or fragments of insects as nourishment, besides the 
usual fluid or very soft food. It is supposed by some naturalists 
that the sterility of the females is more or less due to a dif- 
ference in the food given to them by the workers ; and there is 
some reason for believing that those larvae which eventually be- 
come mothers are fed upon an animal diet ; and the others, which 
become sterile, and turn into workers, are fed upon vegetable 
nourishment. There may be some truth in this opinion, but 
another will be noticed further on. 
One of the most common wasps is the Wood or Bush Wasp 
( Vespa sylvestris). It is a little smaller than the common wasp, 
and it attaches its nest to the branches of trees and bushes, 
hangs it under roofs, or attaches it to the corners of walls. The 
little delicate round nests of this species may often be met 
with in the spring, and a very slight examination of one of 
them will prove that the covering, or envelope, is made up of a 
smooth, grey paper, which is slightly shiny and flexible, and 
perfectly impervious to water. A thick column is found in the 
middle of the inside of the nest, sustaining a single comb, which 
is composed of eight, ten, or twelve cells ; it is the work of the 
