54 BRITISH BEES. 



Sometimes a late autumnal impregnation takes place, 

 for the males of some Andrena, Halicti, and Bombi are 

 found abroad only late in the autumn, and then in fine 

 and recently disclosed condition. 



It is a singular circumstance in the history of some 

 species, that where they abound one season, nidificating 

 on a certain spot in profusion, the following year, per- 

 haps, and the year succeeding that, they will not be seen 

 at all, but yet again a further year, and there they are 

 as innumerable as ever. 



What may control this intermittent appearance it is 

 impossible to conceive, all the conditions of the spot and 

 its surroundings being the same. This I have found to 

 be a peculiarity incidental to many of the aculeate Hy- 

 menoptera. It occurs also in the flowering of many 

 plants which blossom irregularly from season to season. 

 It is a fact scarcely concordant with the observed rapi- 

 dity of the disclosure of the larva from the egg, and the 

 speedy growth, development, and transformation of the 

 latter into the pupa and imago. 



The wild bees appear to be of annual, or of even more 

 restricted duration merely. Of this, however, we have 

 no certainty. The conclusion is derived chiefly from 

 the circumstance that, as they progressively come forth 

 with the growth of the year, they, when first appearing, 

 are in fine and unsoiled condition. There are evidently 

 in some species two broods in the year ; the one in the 

 spring and the other autumnal. In bees without pu- 

 bescence we have not the same guide. But humble-bees 

 are reputed to have a longer life than of one year, and 

 hive bees are said to survive several years, a duration of 

 existence inconsistent with analogy, and which has been 

 repeatedly and strongly denied. 



