52 BEES AND WASPS [CH. 



hexagonal, but near the margins they become irre- 

 gular or nearly cylindrical. The number of combs 

 may be, in a strong colony, as many as twelve, one 

 below the other : about seven is however the usual 

 number. 



Each cell is not tenanted by a grub merely once ; 

 but so soon as the first imago vacates it, the "workers" 

 clear away the remains of the cocoon, and a fresh egg- 

 is deposited by the "queen." The cast skins and mass 

 of excreta are however left in the cell, firmly fastened 

 to the roof. It is by counting these masses that the 

 number of tenants of any given cell is determined ; 

 and it appears that no cell is used more than thrice. 

 When this limit has been reached the walls of the 

 cells are cut away so as greatly to reduce their depth, 

 and frequently the stump of the cell is sealed over 

 with a covering of " paper." In a very strong nest 

 the topmost comb is sometimes completely cut away, 

 its place being occupied by a thick mass of wrappings. 

 The lowest combs, sometimes only one, sometimes as 

 many as six, are composed of cells larger than those 

 in the superjacent tiers: these "royal" cells are 

 destined for the "queens" of the next generation. 

 It appears to depend upon the amount of food 

 supplied to a grub arising from any given fertilised 

 egg whether the resulting female be a "queen" or 

 a "worker." It sometimes happens in a favourable 

 season when the "workers" are numerous and food 



