SOLITARY AND SOCIAL WASPS 



entrance at the bottom. The construction of several (two 

 to four) envelopes with air in between provides the best sort 

 of heat-insulation that can be imagined. Eggs are laid in 

 cells which have only been started, but when the grub hatches 

 and begins to grow the cells are lengthened to keep pace 

 with it. The first cell remains circular in cross-section, but 

 the later ones become more and more regularly hexagonal, 

 each of their walls, except those on the periphery of the 

 comb, being shared with another cell. It can be shown that 

 this arrangement makes possible the most economical use 

 of a given quantity of paper. It seems that as wasps do not 

 vary much in size, they can use their own bodies as a pair 

 of dividers for measuring a standard distance. 



The queen wasp never makes more than about ten to 

 twenty cells, since when the grubs are growing actively it is 

 all that she can do to keep them fed unaided. It seems clear 

 that adult wasps can take only liquid foods, since the entrance 

 to their throat is'too small to admit more than the minutest 

 solid particles. Probably most of their food is nectar from 

 flowers, juices of fruit and sweet things of that sort. But to 

 feed their young they catch and cut up other insects, such as 

 flies or moths. These are pounced on when settled. They are 

 not stung but cut up and chewed into a paste. The wasps 

 will also cut small pieces from dead animals. Probably some 

 of the juices extracted from the paste form a necessary sup- 

 plement to their own diet. Whether the young receive much 

 sweet stuff as well as animal matter is uncertain. The grubs 

 live and grow upside down, since the opening of the cell is 

 at the bottom. When full-grown the grub spins a silken 

 cocoon which forms a white cap across the bottom of the 

 cell and a thin lining to the rest of it. 



The life of the queen with her first cells differs in no 

 important respect from that of a solitary wasp practising 



47 



