HYMENOPTERA. ACULEATA. 229 



The determination of species is a much more difficult 

 matter, and requires close examination. On the one 

 hand, many species very closely resemble each other ; 

 while on the other, great variety in size, colouring, &c., 

 occurs in individuals of the same species. A young and 

 fresh coloured Bee can sometimes hardly be recognised 

 when old and hoary, or when its golden glories are ex- 

 changed for the baldness of age. Besides this, the 

 males are in some cases entirely unlike the females of 

 their own species. 



There is great variety of appearance among the 

 Andrena3, many of them are not unlike the common 

 Hive Bee in size and colouring, &c., but they are gene- 

 rally rather more hairy, while others are sufficiently so to 

 be mistaken by the tyro for small Humble Bees. 

 Black, white, grey, and various shades of golden brown 

 (PL IX., fig. 3, A.fulva), are the usual colours of the 

 hairs, which are variously distributed, some species being 

 thickly clothed all over, while others have the thorax 

 furry, and the abdomen fringed with long hairs, or 

 nearly naked. In one division the species are coloured 

 like the Sphecodes, from which, however, the tufted 

 troehanter easily distinguishes them. All the females 

 are furnished with a thick pollen brush on the hind legs. 

 In size the Andrenae range from that of the Honey Bee 

 down to one-third of its length. The submarginal cells 

 are three in number. All the Andren burrow in the 

 ground, some burrowing alone, and others living in 

 colonies, which very commonly include large numbers 

 of the wasp-like parasitic Bee, Nomada, of which a 

 description will be found in its place. The tunnels of 

 the Andrenae branch out in various directions, and are 

 less elaborately finished than those of most other Bees. 



