Page:Natural History Review (1861).djvu/63

Rh whole race must soon perish. For, if their history were so simple, there seems no reason why a large proportion of young might not survive; and the species would then continually increase in numbers, which is impossible. This argument is, however, far from conclusive, because the increase may be prevented by disease, or by some enemy. On the other hand, there would, under this theory, be no means by which the parasites could pass from bees of one nest to those of another; so that in each species we should have one race infested by Sphærulari, and another free from them; in which case, it can hardly be doubted that the former race would, in the struggle for existence, gradually be supplanted by the latter, and thus, in time, the Sphærulari would all perish.

That the young Sphærulari can live some time after leaving the body of the bee, and without entering any other animal, I ascertained satisfactorily. On the 25th of last May I took some from the body of a B. lucorum and put them in water, where some of them remained alive until the 9th of August, though, during the latter part of the time, they were far from lively. In this case, therefore, they lived in water for more than ten weeks. Whether they would have lived as long in damp earth, I cannot say, but it seems not improbable; and as we know that humble bees often crawl about on the earth under leaves and grass, they may, in this manner, give the young Sphærulari an opportunity of entering them. I tried to solve this question, by wetting humble bees with water containing young Sphærularias; but, partly owing to the difficulty of keeping these insects in confinement alive for more than a few days, and partly, perhaps, from the difficulty of detecting a single young worm in the abdomen of a bee, my experiments were quite unsuccessful.

I had hoped to have thrown some light upon this question, and also upon the metamorphosis, by obtaining some specimens in autumn and winter. Up to the present time, however, I have only found them in May, June, and July. This is partly, perhaps, owing to the fact, that large females are most easily obtainable in these months; and it is unlucky for me that the last two years have been very unfavourable to bees—1860, indeed, so much so, that it is said (Zoologist, September, 1860), to have been the worst year for Hynmoptera since 1828.

I have, however, examined eight large females of B. lucorum in August, and three in October; two of B. terrestris in August, two in September, and two in October; if, therefore, at this season, the Sphærulari were as numerous and as large as in spring and summer, I should almost certainly have found some. If, on the other hand, they were quite small, they may easily have been overlooked.

From all these facts, I am inclined to think that humble bees, when infested with Sphærularia, live for a while as if nothing were the matter; and that only when the young Sphærulari, or the majority of them,