British Bees / An Introduction into the Studies of the Natural History and Economy of the Bees Indigenous to the British Isles

by William Edward Shuckard

The thorax, the second segment, carries all the organs of locomotion. It consists of the prothorax or collar, which carries beneath the anterior pair of legs; the mesothorax, or central division, with which articulate laterally above the four wings, the anterior of which have their base protected by the squamulæ, or epaulettes, or wing-scales, and beneath it carries the intermediate pair of legs; the metathorax, or hinder portion, which has in the centre above, behind the scutellum, the post-scutellum, and at the extremity of this division just above the articulation of the posterior legs is attached the last segment of the insect,—the Abdomen.

The vertex, or crown of the head, is that portion which lies between the upper extremities of the compound eyes. Upon the vertex are placed the stemmata, or ocelli (the simple eyes), in a curve or triangle; they are three in number, and are small, hyaline, circular protuberances, each containing within it a lens; sometimes they occur very far forward upon the face, especially when the compound lateral eyes meet above, as in the male domestic bee or drone. The uses of these simple eyes, from the experiments which have been made, seem to be for long and distant vision. To test their function, Réaumur covered them with a very adhesive varnish, which the bee could not remove, and he then let it escape. He found upon several repeated trials, that the insect always flew perpendicularly upwards, and was lost. Although this was anything but conclusive as to the uses of these eyes, it would seem that by losing the vision of this organ, the insect lost with it all sense of distance.

The compound eyes, seated on each side of the head, extend from the vertex generally to the articulation of the mandibles or jaws, their longitudinal axis being perpendicular to the station of the insect. They vary in external shape and convexity in the several species and genera, although not greatly, and consist of a congeries of minute, hexagonal, crystalline facets, each slightly convex externally, and their interstices are sometimes clothed with a short and delicate pubescence. Each separate hexagon has its own apparatus of lens and filament of optic nerve, each having its own distinct vision, but all converge to convey one object to the sensorium. The function of the compound eyes is concluded to be the microscopic sight of near objects.

The face, which sometimes has a longitudinal carina, or prominent ridge, down its centre, lies between these eyes, descending from the vertex to the base of the clypeus, or nose, but which is without the function of that organ. This clypeus is sometimes protuberant, and from shape or armature, characteristic. This part, however, is not always distinctly apparent, although a line or suture usually separates it above, from the face. At its lower extremity the labrum, or upper lip, articulates, over which it is sometimes produced; and it extends at each lateral apex to the base of the insertion of the mandibles. The genæ, or cheeks, descend from the vertex laterally, behind the compound eyes, to the cavity of the head which contains the lingual apparatus, when folded in repose. These cheeks, at their lower extremity, sometimes embrace the articulation of the mandibles.

Fig. 6.—1, Clavate antennæ;
2, filiform ditto;
a, scape;
b, flagellum.

The antennæ, or feelers, are two filamentary organs articulating on each side of the face and above the clypeus. They comprise the scape (a), or basal joint, and (b) the flagellum or terminal apparatus; the latter consists of closely attached conterminal joints, and usually forms an elbow with the scape; collectively these joints number twelve in the female and thirteen in the male. They are all of various relative lengths, which sometimes aid specific determination. The scape, however, is usually much longer than any of the rest, and in some males has a very robust and even angulated shape. A description of the antennæ always enters into the generic character; they usually differ very materially both in length and form in the sexes. They are often filiform (2), but more generally subclavate (1), and sometimes distinctly so, and where they have the latter structure it is found in both sexes. They constantly differ in the species of a long genus (Andrena, Normada, Halictus). In the male of the genus Eucera, they have a remarkable extension, being as long as the body, whereas folded back they are rarely so long, or not longer than the thorax in other males, speaking in reference only to our native kinds. In the females they are not often longer than the head. It is in the males of the genus Halictus that they take the greatest extension. In the male of the genus Eucera, we also find the remarkable peculiarity of the integument of some of the joints being distinctly of an hexagonal structure,—a peculiarity often observable in natural structures. In this case it may refer to the sensiferous function of the organ, and to which I shall have occasion to revert when I speak of the senses of our insects. We sometimes find the joints of the antennæ moniliform, something like a string of beads, or with each separate joint forming a curve, or with their terminal one, as in Megachile, greatly compressed.

The relative lengths of the joints often yield conclusive separative specific characters, and which may be very advantageously made available, especially where other distinctive differences are obscure, and in cases where the practised eye observes a distinction of habit, evidently specific, although it is difficult to seize tangible characteristics.

The trophi are the organs of the mouth of the bee collectively. When complete in all the parts, as exemplified in the genus Anthoptera, they consist of the labrum, or upper lip; the epipharynx, or valve, falling over and closing the aperture of the gullet; the pharynx, or gullet, which forms the true mouth and entrance to the œsophagus; the hypopharynx which lies immediately below the gullet and assists deglutition; the labium, or lower lip, and the true tongue. These parts are all single; the parts in pairs are the mandibles, the maxillæ, the maxillary palpi, the labial palpi, and the paraglossæ.