206 THE BOOK OF NATURE STUDY 



Meanwhile from the summit of the pillar a balloon-shaped cover- 

 ing has been made, surrounding the comb and permitting access 

 to it at the bottom only through a circular hole. A second and 

 a third covering of similar shape are added outside the first, 

 narrow air spaces separating each from its neighbour. These 

 wrappings protect the comb and its contents from enemies, drops 

 of moisture, and especially from chill by virtue of the non-con- 

 ducting property of the enclosed air. In one of the angles 

 of each cell the " queen " deposits a single egg, glueing it firmly 

 in place. After a few days the length of time depending upon 

 the temperature there hatches from the egg a small white legless 

 grub, which, however, does not entirely quit the egg shell, but 

 hangs head downwards from it, keeping the last segments of the 

 body still within the shell, and thus avoids falling headlong 

 out of its cradling cell. The grubs possess jaws, and are fed by 

 their mother on such animals as caterpillars, flies, aphides, and 

 carrion of every kind, while she sustains herself chiefly on the 

 nectar of flowers and other sweet substances. As the grubs grow 

 they twice cast off their skins as these become too tight for the 

 body, and thrust the empty husk up against the roof of the cell. 

 When first completely free from the egg shell they assume a 

 slightly curved attitude, so as to press against the walls of the 

 cell and thus maintain their position ; in this they are helped 

 by a special leg-like sucker at the end of the abdomen, and also 

 by the mandibles. Eventually they become so large that almost 

 the entire surface of the body impinges upon the cell walls, while 

 the head may project downwards beyond the margin. As the 

 increasing size of the grubs demands it, the cells are made longer 

 by the queen adding fresh " paper " to their rims. Eggs and 

 grubs in all stages of development can be obtained from the combs 

 of wasps' nests taken in August and September. A fully grown 

 grub consists of thirteen segments, excluding the head, 

 is white, fleshy and legless ; it has lateral breathing holes, and 

 maintains a series of regular movements up and down within 

 the cell in order to promote the outward and inward flow of air. 

 The head carries a pair of small eyes, and a pair of mandibles, 

 whose shape in the youngest larvae differs from that assumed 

 subsequently in having the median of the three teeth very long 



