ON COLOUR
There is but little tendency towards brilliant coloration amongst our native aculeates. No doubt our comparatively high latitude accounts for this to some extent, as also the fact that the aculeates do not, as a rule, elsewhere assume great brilliancy. Even in the tropics and other warm regions, where bright green, blue or coppery coloured species occur, they are comparatively few in number. In this country metallic colours are to be found in less than a dozen species, and in most of these it exists only as a tinge. Amongst our ants and wasps it does not exist at all, unless the slight bronziness of the typical form of Formica fusca be so considered. The fossors can exhibit only a bluish tint in Mutilla Europæa ([pl. A], 4, 5), and a slight bronzy tinge in two of quite the smallest species, Miscophus maritimus and the ♂ of Crabro albilabris. The bees can do a little better; five species of Halictus have a distinctly
bronzy head and thorax, and in three the bronzy colour extends to the abdomen; there is also another with a very dull green tinge on the thorax; besides these there is a little bright blue bee, Ceratina (unfortunately a great rarity in this country) and two or three species of Osmia, showing more or less tendency to bronziness, and one which is distinctly bluish; but, considering our indigenous species number nearly 400, this is a very small, and compared with other countries I should think an abnormally small, proportion.
Species with bodies banded like a wasp's are much more abundant—no less than eighty of our native kinds having this style of coloration. The bands may be reduced to lateral spots, but such cases, I think, are only modifications of the banded scheme.
Black species with a more or less pronounced red band across the body number about seventy, and a general testaceous or yellowish colour occurs in a few ants, but not elsewhere among the British aculeates. Nearly all the rest are black or dark brown so far as the actual surface of the body is concerned; but amongst the bees
there is often a dense clothing of coloured hairs sometimes so dense that the surface of the body may be rendered invisible. These coloured hairs may be distributed into brilliant bands, as in the humble bees, or they may be uniformly black, as in some of their varieties and in the females of the spring species of Anthophora ([pl. D], 25), or entirely red as in Andrena fulva ([pl. B], 16), or black on the thorax and red on the abdomen as in Osmia bicolor ([pl. D], 28), or vice versâ as in Andrena thoracica, etc., but the most usual condition is that where the hairs form more or less pale bands along the joints of the segments, either immediately above or below them or both; sometimes these bands are very obscurely indicated, and visible only in certain positions. At others they are vividly white; to a certain extent this banded condition recalls the waspy coloration. The hairs, however, of the bands are rarely yellow, but as a rule greyish or white, or of a grade of colour slightly paler than those of the disc. There are some rather interesting points which arise out of this rough analysis. Among the bees, all the species which have a waspy coloration are cuckoos, with only one exception (Anthidium)
([pl. D], 27), as are also nearly all those which have red bands. With the exception of the males of three species of Halictus, and both sexes of three or four species of Andrena, all the red-banded forms belong to the genus Sphecodes ([pl. B], 11), which is a cuckoo genus. The red coloration occurs chiefly on nearly naked surfaces; this is specially noticeable in those bees which have two varieties, such as Andrena rosæ, one dull coloured and the other red-banded: in these cases the dull form is hairy and the red nearly naked. The greatest proportionate number of banded species occurs amongst the fossors, and these are seldom clothed with hairs to any extent. These bands seem to me probably to depend a good deal on retarded development. Dark and hairy bands, both as a rule, follow the joints of the segments, as stated above. I only say as a rule, as there are many where the banding does not follow this principle, but in far the larger majority the bands, whether of dark colour or hairs, are apical. As the segments overlap at the joints it is evident that their discs would tend to mature more rapidly than the overlapping bases and apices,
and the longer period spent in hardening and drying of the overlapping parts would favour the development of dark pigment and of hairs. Many species have the extreme apices of the segments pale, but with the apical integument so very thin, often looking nearly transparent and membranous, that its development would be very rapid. Again, in the case of red coloration, the red generally occurs on the discs of the segments, the apices and sides often being dark, and in cases where in one species both black and banded forms occur, with intermediate varieties, the last remnant of red colour is generally situated in the centre of the segment. By far the gayest effect is displayed by our humble bees, and, but for them and a few of the species of Andrena and the wasp-coloured species, our aculeates would be a very sombre lot.