ANTS, BEES AND WASPS 177 



The genera Bombus and Melipona are also social in their habits. 

 The genus Bombus, of which there are several species, includes 

 the well-known Bumble, or Humble, Bees. They differ in many 

 ways from the Hive Bees (Apis). The colony lasts for a season 

 only, none of the workers surviving the winter. The young fer- 

 tilised queens hibernate under moss or litter during the cold months 

 of the year, and each one in the ensuing spring starts a new colony 

 by herself. The nest may be made in a hole in the ground or 

 under a heap of moss. The queen constructs a few waxen cells, 

 in which she places several eggs, after having first stored the cells 

 with a cake of honey and pollen. Quite unaided, she continues 

 to build cells, lay eggs, and feed the larvae as they emerge, until 

 the first batch of workers have completed their metamorphosis 

 and are ready to assist her. These workers do not differ struc- 

 turally from the queen to the same degree as hive bees do ; they 

 are more or less imperfect females, and to a certain extent are 

 often capable of supplementing the queen in egg-laying. As 

 the colony increases the queen confines herself to egg-laying, 

 the workers building the cells, attending to the larvae, and fetching 

 provisions. The nest of a Bumble Bee is not so well planned 

 or so orderly in appearance as a colony of Hive Bees. The cells 

 are of different shapes and sizes. Brood cells are never used 

 twice for rearing larvae ; fresh cells are built on the ruins of the 

 old ones, or some may be used for storing honey and pollen. An 

 average colony of Bumble Bees in the autumn contains about 

 120 individuals ; of these 25 may be females, 36 males, and the 

 rest workers ; but a prosperous colony may number between 

 300 and 400. 



Living in the nests of Bombus, and on friendly terms with the 

 rightful inmates, may often be found a certain number of bees 

 belonging to the genus Psithyrus. In appearance the Psithyrus 

 resemble their hosts, but their hind legs are not formed for carry- 

 ing pollen, and they take no part in the work of the colony beyond, 

 in some cases, constructing a few cells in which to deposit their 

 eggs, the larvae of these parasitic or commensal bees being brought 

 up by the accommodating Bombus. There are no workers amongst 

 these curious bees only males and females ; and, strangely enough, 

 the Bombus never seems to object to the presence of the Psithyrus 

 in the nest, although, as the bees of the last-named genus do no 



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