2 o8 THE BOOK OF NATURE STUDY 



up into pulp by the mandibles of the workers and moulded by 

 the same organs into " wasp-paper." Nearly any fence or gate 

 post that has not been tarred or painted may be seen to be streaked 

 with little scars running parallel with the " grain " of the wood, 

 and caused by wasps gathering building material. The wrap- 

 pings and their enclosed air have so great a power of resisting 

 the passage of heat, that the occupants of a large nest which 

 was placed by the writer for some hours in a hot oven were in 

 no way incommoded, but their development accelerated. The 

 entrance to the nest is always at or near the bottom, and all 

 the cells of every comb face downwards towards it, though a 

 few at the margins are often rather obliquely set. Room is 

 left sufficient for the passage of the wasps between the successive 

 combs, and between their margins and the external wrappings ; 

 these intervals are measured by the wasps while at work, the 

 hind-legs being extended for the purpose. The thickness of 

 the sheets and cell-walls is gauged by tapping the antennae 

 on each side simultaneously, much as we gauge the thickness 

 of materials between finger and thumb. Each cell may be used 

 thrice for grub rearing, as may be proved by extracting from the 

 roof the cast-off larval and pupal skins of its successive tenants. 

 Hence in a comb of five or six inches diameter there will be found 

 round the circumference (the newest part): (i) small cells con- 

 taining eggs or very small larvae for the first time ; passing to- 

 wards the centre of the comb, and arranged approximately in 

 concentric circles, occur; (2) cells containing larger and larger 

 grubs, for the first time ; (3) " capped " cells containing pupae, 

 or imagines ready to emerge, also for the first time ; (4) empty 

 cells from which wasps have emerged ; (5) cells occupied by eggs 

 or very small larvae, for the second time ; (6) cells with larger 

 grubs, for the second time, and so on. Every comb is begun 

 at its middle, which is therefore its oldest part. When cells 

 have been used thrice they are cut down and their material used 

 again, the foundation (top) only being left. Sometimes the mouths 

 of old cells are covered up with wasp-paper, and so an air- 

 space enclosed ; this is especially the case in the two oldest combs 

 at the top of the nest. All the debris of the nest and much of 

 the excreta of the wasps are discharged on to the soil below the 



