INSECT COMMUNITIES 291 



itself of the full accommodation which the cell affords. 

 It has only two grasping organs, namely, its jaws and a 

 kind of sucker foot at its tail-end ; so that if it relaxes 

 its hold at one extremity before making fast with the 

 other, it immediately falls headlong from the cell. Such 

 accidents are by no means rare ; and one would think that 

 a daily shower of helpless infants from the ceiling would 

 suffice to teach the least attentive nurses that vertical 

 cradles are unsafe. But the workers seem to accept these 

 accidents as a matter of small moment, and rarely attempt 

 to replace the fallen grubs. They usually carry them out, 

 and drop them at some distance from the nest, exactly as 

 they do with refuse. 



The lucky grub which succeeds in planting its sucker 

 foot firmly against the roof of its cell soon has nothing to 

 fear, for it grows so fat that it completely fills its cradle. 

 It is regularly supplied with food by its nurses, the diet 

 consisting mainly of the softer parts of insects, varied by 

 an occasional mouthful of nectar or fruit juice. From ten 

 to fourteen days after hatching the grub is full-fed, spins 

 a silken cap over the mouth of its cell, and changes to a 

 pupa. The whole metamorphosis, from egg to perfect 

 insect, occupies rather more than three weeks under 

 favourable conditions of temperature. Like the hive-bee, 

 the newly emerged adult wasp passes a period of proba- 

 tion within the shelter of the nest ere she goes forth to 

 forage for the benefit of the community. When young 

 and vigorous she is chiefly engaged in building ; but ere 

 long, probably in less than three weeks, her salivary glands 

 become exhausted, and her powers of paper-making fail. 

 She may now be styled an " old wasp," and devotes her 

 remaining energy to the care of the rising generation. 



A prosperous wasp colony, at the close of the summer, 

 consists of thousands of workers, each a direct offspring of 



