THE SOCIAL WASPS 37 



a substance fitted for the walls of their cells ; 

 they will also chew paper, and the experiment 

 has been tried of giving them coloured papers, 

 which resulted in stripes of colour appearing 

 in their nests. The different species vary some- 

 what in the architecture of their nests ; but 

 they are built very much on the same general 

 plan. The population of some underground 

 nests is very large. The Rev. G. A. Crawshay 

 estimated the number in a large nest of Vespa 

 vulgaris, which he took on September 20, 1904, 

 at about 12,000 ; of these he actually counted, 

 including eggs and larvae, 11,370, and estimated 

 the rest as having left the nest and escaped, 

 so that anyhow the computation cannot 

 be far wrong. This, however, was probably 

 a very large nest. The cuckoo wasp (Vespa 

 austriaca), formerly known as V. arbor ea, is an 

 associate of Vespa rufa ; its habits had been 

 suspected for a long time, but Mr. Robson set 

 all doubts at rest by finding the nymphs of the 

 cuckoo in the actual nest of rufa. It is a 

 rare species in the south, but far from uncommon 

 as one goes north, and also in Ireland, where the 

 relationship of the host and cuckoo have been care- 



