In colour the humble bees vary remarkably, the variation occurring chiefly in the females. This variation is not so noticeable in this country, although in many species even here the variability is very great, but when we trace a common species such as terrestris, which varies very little here, over a large area such as the Palæarctic region its liveries are so diverse that its females have been treated as belonging to many different species. In the Siberian district its yellow bands become of a pale, almost whitish or straw colour, and the whole appearance of the insect is altered. If, instead of going north, we go to the Mediterranean region we find a large, fine form tolerably common, with bright yellow hairs on the legs. In Corsica
again we find a quite different form; entirely black except for the bright red hairs on the apex of the body, and bright red tibiæ, clothed with red hairs. In the Canaries another coloration occurs: the whole insect is black with the exception of the apex of the body which is clothed with white hairs; but in all these the male varies comparatively little. In the Siberian and Canary forms it resembles the female, but in the others it varies very little from some varieties we find here. A rather similar series of varieties occurs in Bombus hortorum, another species little liable to variation here. In Italy and south-east Europe a form with entirely black body and black wings occurs, and in Corsica a black form with reddish hairs on the apical segments. The male keeps throughout very constant to its normal coloration. The tendency to vary towards an entirely black form seems to exist in nearly all the species, although in Britain black varieties of some are very rare.
THE BEES WITH BIFID TONGUES
In this country we have only two genera in which the tongue is bifid at the apex, and on this account they are kept together as close allies in our classification. They are, however, very different in general appearance. One of these groups is called Colletes, on account of its habit of lining its cells with a gluey material, the other, Prosopis, on account of the markings on the face. The various kinds of Colletes are densely clothed on the head and thorax with brownish hairs, and the segments of the body have whitish bands composed of a dense, tight-fitting, duvet of hairs ([pl. B], 10). There is in this country only one exception, a large insect like a hive bee, but rarely met with, its headquarters being the Wallasey Sandhills near Liverpool, and other localities in Lancashire. All the species tend to colonize; some building in huge colonies
in sandy cuttings, etc. They are preyed upon by a pretty little cuckoo bee called Epeolus ([pl. B], 19), which is black, ornamented with brownish red and whitish spots. One of our best known species, Colletes fodiens, can often be found in abundance on the heads of ragwort along the sea-coast in July.
The other genus Prosopis is outwardly entirely unlike Colletes: its species are nearly all very small coal-black insects, with scarcely any noticeable hairs, rather unusually narrow and cylindrical in form; they emit a peculiar, agreeably scented fluid when handled; in the males the face is almost always white or yellow, in the females there is generally a yellow spot on each side near the eye. These little creatures are especially fond of burrowing in bramble stems. They like those which have been cut off in trimming the hedges, because in them the pith is exposed and they can burrow their way into it without gnawing through the wood. If any one, going along a hedge which has been trimmed, containing a lot of brambles, in the autumn or winter, would examine the cut-off ends they would soon find some with holes in them. These
may be the work of Prosopis, but there are other bees and fossors which also burrow in this way. So the stems should be brought home and opened. Then the Prosopis cells may be known by the fine membranous pellicle which surrounds them, but possibly even then a little jewel-bee cuckoo may be found in possession of the cell, instead of the rightful owner. When these little bees emerge they are generally to be found on wild mignonette, bramble flowers or those of the wild parsley tribe. Some are very common, others of great rarity. The males of this genus seem to have a peculiar tendency to develop eccentricities in the shape of the first joint of the antennæ, or feelers, some having it expanded and concave, others rounded but thickened towards the apex; in only one British species, P. cornuta, does the female show any special peculiarity of form, but in this the face is produced on each side between the eyes into a distinct horn-shaped process. In the females there is scarcely any indication of pollen brush, and for this reason they used to be considered as possessors of cuckoo instincts, but there is now no doubt of their industrious habits; but
there is no other genus of industrious bees in this country, with the exception of Ceratina, with so little specialization for pollen collecting.