234 TRANSFORMATIONS OF INSECTS. 



and others of the same form are built close together on a horizontal 

 floor, and they arc 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 veiy strong sting. The larvae 

 are feeble creatures ; nevertheless, the head of the wasp larva is 

 stronger and larger than that of the other Hyinowptcra ; even 

 their mouth-pieces are stouter, and this enables them to receive 

 bits of fruit or fragments of insects as nourishment, besides tlie 

 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 larvas 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 sylvcstris). 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, ^\•hich 

 is composed of eight, ten, or twelve cells ; it is the work of the 



