226 THE BIOLOGY OF INSECTS 



observations made by H. Brauns on South African species 

 of Allodape which nest, like our native Osmia, in hollow 

 plant stems, but make no partitions between the successively 

 laid eggs so that the nest is not divided into chambers. In 

 some species a ** food-packet " is provided for each grub at 

 the time of egg-laying. In others the mother arranges the 

 eggs in such a way that the grubs, when hatched, direct their 

 heads towards the entrance of the nest, and she brings to 

 them at intervals lumps of " bee-bread " on which they 

 feed in common. A further stage of development in be- 

 haviour is attained by species of Allodape whose females 

 feed their grubs individually, and produce an *' affiliation 

 of the offspring with the mother to form a co-operative 

 family." No workers, however, are produced among these 

 incipiently social bees, and it must be admitted that the 

 three truly social groups — the bumble-bees, the stingless 

 bees, and the Hive-bee with its wild allies — stand markedly 

 distinct from all the rest of the family. A feature of struc- 

 ture in relation to life conditions that characterises them is 

 the possession of abdominal glands that secrete the well- 

 known bees-wax used by the insects for building the 

 chambers of their combs. 



The stoutly built hairy bumble-bees (Bombus and 

 allies) are well known to every country rambler, and the 

 habits of our British species have been excellently described 

 by F. W. L. Sladen (19 12). The societies of these insects 

 in temperate climates are in most respects parallel to those 

 of the social wasps, in that a queen, reared and paired in 

 the previous summer, survives the winter in some sheltered 

 spot and starts a new family in the spring. The young 

 queen chooses in autumn a bank with a northern aspect 

 on which to seek a burrow for hibernation ; on a south- 

 facing slope she might be awakened by the midday sun 

 too early in the year and perish in a sudden frost. For the 

 site of her nest (Plate IX) she seeks some convenient under- 

 ground cavity, often the deserted burrow of a field-mouse, 

 and begins her building work by moulding a lump of 

 moistened pollen on which she erects a waxen wall enclosing 



