64 THE EEPORT OF THE No. 36 



Pollen is also stored in the old cocoons or in specially constructed waxen cells, 

 which are by some species attached to the bunches of larva?. The photograph here 

 shown is of a nest of Bomhus lapidarius. Notice the wax-covered bunches of larvae, 

 the clusters of cocoons and the waxen honey-pots filled with glistening honey. In 

 one place an old cocoon containing pollen may be seen. 



The number of workers produced varies according to the species. In some of 

 the underground dwelling species, for instance, Bombus lapidarius, it amounts to 

 about 300, while in some of the surface nests it does not exceed 60. The 

 males and queens are reared after the workers, and they h^ave the nest as soon 

 as they are fledged. By this time the workers are getting old and worn and they 

 die off rather quickly. Finally the old queen herself perishes, but this event is 

 often preceded by a kind of Indian summer in which, having no more egg's to lay, 

 she becomes quite lively and youthful looking again. Death, when at last it 

 comes, is probably painless. A cold night and an empty cupboard caused torpor, 

 as it did on many occasions in the early part of her career, but this time there is 

 no awakening. And so ends the recently busy community. 



Bumble-bees have many enemies. Perhaps the greatest are of their own kind. 

 In the case of two of the commonest British species, Bomhus terrestris and lapi- 

 darius, a queen finding a commencing nest of her own species attaches herself to 

 it. The old queen remains friendly with the intruder until she has eggs to lay. 

 Then a battle royal takes place and one of the queens stings the other to death. 

 I have found as many as twenty dead terrestris queens that have been killed in this 

 way lying under a terrestris nest. There is a whole genus of lazy bumble-bees 

 named Psithyrus whose nature it is to prey on the industrious bumble-bees in much 

 the same way. Each species of Psithyrus preys on a particular species or group 

 of species of Bombus. The Psithyrus is destitute of the pollen-collecting apparatus 

 on the hind legs and is quite incapable of establishing a nest and providing food 

 for her young. She is a heavy, lazy, dark-winged individual. Her skin is ex- 

 ceedingly thick and hard, the plates covering the abdomen fitting closely over one 

 another, forming a coat of mail to protect her from the stings of the Bombus 

 queen. She prefers to find the Bomhus nest when a few workers have hatched. 

 Here she devotes herself to winning popularity, and as soon as she finds that 

 sufficient eggs have been laid to produce a good number of workers she murders 

 the unfortunate Bombus queen and compels the ^vorkers to become her slaves and 

 rear her young, for she producas no workers of her own kind, only males and 

 queens. 



Sometimes the Psithyrus fails to find the Bombus nest until many workers 

 have hatched. These attack her furiously and generally succeed by long-continued 

 efforts in killing her by stinging her in some joint between the harness, such as the 

 neck or insertion of the wings. It is a remarkable fact that the Psithyrus queens 

 do not fight among themselves. 'Should more than one find the same nest the others 

 slink off to search for other nests, leaving the first one in possession. Should a 

 Psithyrus queen find a nest of a different species of Bombus to that on which she 

 naturally preys she lodges in it night after night, compelling the Bombus to share 

 with her the food the latter has collected until she finds a nest of her true host. 

 Another striking fact is that the Psithyrus usually resembles in colour the species 

 of Bombus ,on which it preys. This mimicry cannot be for protection from the 

 Bombi for they meet only in the nest where it is quite dark. Probably the mimicry 

 is due to the slightly greater protection from the attacks of birds, most of 

 which avoid bumble-bees, afforded bv donning the warning livery of their more 



