It would seem from the facts that have been recorded, and the close investigations made, that in some instances the next year’s bee is already disclosed and in the imago state, in the autumn of the existing year, so that it is ready, upon the first genial weather in the spring, to work its way out of its nidus, and take its part in the duties it has to perform. Whether this be for the economy of the food to the larva, or the saving of labour to the parent in gathering it, or that it would be prejudicial for it to lie dormant in the pupa state during the winter is not known, but thus in many instances it is. Sometimes a late autumnal impregnation takes place, for the males of some _Andrenæ_, _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, perhaps, 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 _Hymenoptera_. 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 rapidity 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 pubescence 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.