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.
THE DEVELOPMENT OF INSECTS FROM THE EGG
Although this and the following chapter may not be interesting to all my readers, I think it is only right to add some remarks on the structure and classification of insects, so that any one who wishes to follow up the subject may gather a few general ideas which may induce them to take up some technical and scientific work in which they will get fuller and more exact data on the difficulties which are involved in such simple questions as "What is an insect?" "How are the different orders of insects distinguished from each other?" "What is a species?" etc.
To realize the characters of an insect in its perfect or "imago" state, we may for the moment forget what often seems to be its most important features, and which are frequently its most extensive parts, viz. its limbs or
appendages; by limbs are meant its wings, legs, horns or antennæ, jaws or mandibles, etc.: strip these all off, and we have a limbless trunk, which many would not recognize as belonging to an insect at all; still this limbless trunk possesses characters which assert its insect nature, as it may be known from other limbless trunks by being divided into three parts by two great transverse divisions; in most insects these are extremely well marked, and in all they have a very real existence. The parts thus divided off are known by the names of head, thorax, and abdomen. Anybody knows how easy it is to break off the head or body of a dried insect. Now the head or body breaks off at one of these divisions, and it is this partitioning of the body into three sections which makes one of the strongest characters in the definition of an insect. The three parts, thus divided off, each possesses special functions in the life of the creature. In the head are contained the principal organs of sense and brain; in the thorax, the organs of locomotion; and in the body those of digestion, reproduction, etc.