48 BRITISH BEES. 



bees, as in Dasypoda, Panuryus, Eucera, Anthophora, etc, 

 etc., it is conveyed upon the posterior legs, we do not 

 know ; we can only surmise that it is either to save the 

 insect, in the former case, the labour of constructing a 

 larger cylinder for nidification, so to prevent the possi- 

 bility of its being rubbed off from the external surface 

 of the legs, did these carry it, in entering the burrow, 

 it being protected from this abrasion by being placed 

 beneath the venter. In such insects the abdomen is 

 usually truncated at its origin, or even hollowed within 

 its base, thus to meet the projection of the metathorax, 

 enabling it to draw itself closely up together, making 

 the abdomen and metathorax, as it were, cohere. A 

 different form of abdomen occurs in those bees which 

 carry the pollen on their posterior legs. It is then more 

 or less elliptical or lanceolate, which form permits the 

 legs to be drawn up towards the metathorax within the 

 space that kind of form furnishes, which, by this diffe- 

 rent but equivalent arrangement, meets the same object. 

 The similarity of the adjustment of the abdomen to the 

 metathorax to that of Megachile, etc. in Apis and Bom- 

 bus, by which insects the provision is also carried on the 

 posterior legs, results from the totally different economy 

 and habitation of the social bees, to which this structure 

 is necessary for many purposes. 



If we observe this same peculiarity of structure in the 

 cuckoo, or parasitical bees, it is because we find resem- 

 blances where there are alliances. Thus, the male 

 artisan bees, although not assisting in the labour of 

 constructing the apartments, have similarly dilated man- 

 dibles to those of their females. So also, in the form 

 of the abdomen, the Nomada are like the Andrena 

 and Halicti, upon which they are chiefly parasitical. 



