INSECT COMMUNITIES 289 



fashion more cells and to lay more eggs. A time comes, 

 however, when her powers of paper- making fail ; but this 

 is coincident with the maturing of the older grubs, which 

 change to pupa?, and issue from their cells as fully 

 equipped workers. Then the queen devotes all her 

 energies to the task of egg-laying, while the workers 

 feed the grubs, extend the nest, and labour to promote 

 the common weal. The original comb of cells formed by 

 the queen is widened, and new combs are suspended from 

 it by papier-mache stalks. 



It is a peculiarity of wasp architecture that although 

 the nest grows steadily from day to day it never appears 

 unfinished. The outer covering is always round, shapely, 

 and perfectly closed, save for the single entrance hole 

 below. As the combs are extended, the protecting cover 

 is gradually cut away from within and replaced by fresh 

 layers from without. This method necessitates a much 

 greater expenditure of labour and material than would be 

 needed if the nest could be planned on a much larger 

 scale at the outset, especially as wasps rarely use over 

 again the old paper that they cut away. But the nest 

 must be kept constantly closed in order that the grubs 

 may be sheltered from cold and draught. Moreover, the 

 labour necessary for conducting building operations on an 

 extensive scale is not forthcoming during the early periods 

 of the nest's history. 



As the nest grows steadily from day to day, it is clear 

 that the workers must devote much time to the enlarge- 

 ment of the cavity which contains it. Fragments of soil 

 and small stones are carried out bodily ; but those which 

 are too heavy for the insects to lift are carefully under- 

 mined, and allowed to gravitate to the floor of the cavern. 

 If it were possible to make a clean cut right through a 

 bank containing a populous wasps* nest, we should obtain 



T 



