THE SOCIAL INSECTS 



progressive provisioning, but when the first workers bite 

 their way out through the cocoon a real social unit has 

 arrived. With the help of the workers the comb begins to 

 grow rapidly, and a new one will soon be started. To contain 

 the combs, the envelopes will be reconstructed: the paper 

 is chewed away and used with new material to make bigger 

 ones. The queen gradually stops leaving the nest and soon 

 performs no duty beyond egg-laying. Later in her life, when 

 she has been laying eggs rapidly for a long time, her abdomen 

 takes on a discoloured greasy look and she loses all power of 

 flight, so that the old queen is easy to recognise. 



The second comb starts as a pillar hanging from the centre 

 of the first comb, and the process of growth is much the same 

 as in the first ; but large combs are always supported from 

 the one above by several pillars, and their edges are attached 

 to the envelope by small lateral struts. The workers get from 

 one comb to the next by crawling round the edge between 

 the comb and the envelope. As the nest grows, it is nearly 

 always necessary for the wasps to enlarge the hole in which 

 it is hanging. They do this by bringing in water to soften 

 the earth, and in a populous nest workers can often be seen 

 flying out one behind the other carrying little pellets of mud. 

 A big root or stone which they cannot remove may cause 

 the nest to acquire an irregular shape. 



As the comb starts from a cell near its centre the first eggs 

 are laid here too, and as a result concentric rings of develop- 

 mental stages are often seen in a comb. The centre may 

 consist of cocoons, surrounded by rings of grubs getting 

 progressively smaller towards the periphery, till finally there 

 are rings of cells either with eggs or not yet occupied. How- 

 ever, after a new worker has bitten its way out of the cocoon, 

 the cell is cleaned up and used again, so that in a somewhat 

 older comb the central cells will contain eggs once more, 



