I SOCIALES NESTS OF BOMBUS 57 



prejudicial to them. According to Smith, the average number 

 of a colony of B. iiiuscorum in the autumn in this country is 

 about 120 — viz. 25 females, 36 males, 59 workers. Xo mode 

 of increasing the nests in a systematic manner exists in this 

 genus ; they do not place the cells in stories as the wasps do ; 

 and this is the case notwithstanding the fact that a cell is not 

 twice used for the rearing of young. When the ground-space 

 available for cell-building is filled the Bomlms begins another 

 series of cells on the ruins of the first one. From this reason 

 old nests have a very irregular appearance, and this condition of 

 seeming disorder is greatly increased by the very different sizes 

 of the cells themselves. We have already alluded to some of 

 these cells, more particularly to those of different capacities to 

 suit the sexes of the individuals to be reared in them. In 

 addition to these there are honey - tubs, pollen -tubs, and 

 the cells of the Psithyrus (Fig. 23), the parasitic but friendly 

 inmates of the Bonibiis -we&t^. A nest of Boiyibus, exhibiting 

 the various pots projecting from the remains of empty and 

 partially destroyed cells, presents, as may well be imagined, a very 

 curious appearance. Some of the old cells apparently are partly 

 destroyed for the sake of the material they are composed of. 

 Others are formed into honey- tubs, of a make-shift nature. It 

 must be recollected that, as a colony increases, stores of pro- 

 visions become absolutely necessary, otherwise in bad weather 

 the larvae could not be fed. In good weather, and when flowers 

 abound, these bees collect and store honey in abundance ; in 

 addition to placing it in the empty pupa-cells, they also form 

 for it special receptacles ; these are delicate cells made entirely 

 of wax filled with honey, and are always left open for the benefit 

 of the community. The existence of these honey - tubs in 

 bumble-bees' nests has become known to our coimtry urchins, 

 whose love for honey and for the sport of bee-baiting leads to 

 wholesale destruction of the nests. According to Hoffer, special 

 tubs for the storing of pollen are sometimes formed ; these are 

 much taller than the other cells. The Psitliyrus that live in the 

 nests with the Bomhus are generally somewhat larger than the 

 latter, and consequently their cells may be distinguished in the 

 nests by their larger size. A bumble-bees' nest, composed of all 

 these heterogenous chambers rising out of the ruins of former 

 layers of cells, presents a scene of such apparent disorder that 



