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

Fig. 7.—Trophi and their unfolding.
a, labrum;
b, epipharynx;
c, pharynx;
d, hypopharynx;
e, mandible;
f, maxillæ;
g, maxillary palpi;
h, mandible;
i, cardium;
k, labium;
l, labial palpi;
m, paraglossæ;
n, tongue.

The labrum, or upper lip, is attached by joint to the apex of the clypeus; it has a vertical motion, and falls over the organs beneath it, in repose, when it is itself covered by the mandibles. It is usually transverse in form, but is sometimes perpendicular, especially in the artisan bees. It takes many forms, sometimes semilunar or linear, emarginate or entire, convex, concave, or flat, and is occasionally armed with one or two processes, like minute teeth projecting from its surface, but of what use these may be we do not know. In the female of Halictus, it has a slightly longitudinal appendage in the centre. It is usually horny, but is sometimes coriaceous or leathery. This labrum often yields good specific characters.

The pharynx, or gullet, is a cavity immediately beneath the epipharynx, which articulates directly under the base of the labrum, and which closes the pharynx from above, and immediately beneath this cavity is another small appendage, almost triangular, which receives the food or honey from the canal conveying it from the tongue, or directly from the mandibles, when it is masticated, and helps it forward to the pharynx to be swallowed. The epipharynx closes this orifice from above, the labrum then laps over it and the articulation of the lingual apparatus, both which are further protected in repose by the mandibles closing over the labrum. This triple protection shows the importance nature attaches to these organs. The more direct portions of the lingual apparatus are the labium, or lower lip, which forms the main stem of the rest, and articulates beneath the hypopharynx, and is beneath of a horny texture; it forms a knee or articulating bend at about half its length, and has a second flexure at its apex, where the true tongue is inserted. This labium is extensible and retractile at the will of the insect, and lies inserted within the under cavity of the head when in complete repose, and the insect can withdraw or extend a portion or the whole at its pleasure. Attached on each side, at its first bend or elbow, lie the maxillæ, which, for want of a better term, are called the lower jaws, and perhaps properly so from the function they perform; for at the point of their downward flexure, which occurs at the apex of the labium, and where the true tongue commences, they each extend forward in a broad, longitudinal membrane, partly coriaceous throughout its whole length, and these, folded together and beneath, form the under sheath of the whole of the rest of the lingual apparatus in repose, and often lap over its immediate base when even it is extended. Externally continuous, the line of these maxillæ is broken at the point of flexure at the apex of the labium, by a deep sinus or curve, and within this is inserted the first joint of the maxillary palpi. The portion of the maxillæ extending forwards, hence takes several forms, usually tapering to an acute point, but sometimes rounded or hastate, according to the structure of the tongue, to which they form a protection.

The maxillary palpi are small, longitudinal joints, never exceeding six in number, and generally in the normal or true bees not so numerous. They vary in relative length to the organ to which they are attached, and usually progressively decrease in length and size from the basal ones to the apical, but each joint, excepting the terminal one, is generally more robust at its apex than at its own special base. The function of these maxillary palpi is unknown. They are always present in full number in the Andrenidæ, and in some few genera of the true bees, but they vary from their normal number of six to five, four, three, two, and one in the latter; and it is curious that they are most deficient in those bees having the most complicated economy, as in the artisan bees and the cenobite bees; they thus evidently show that it is not a very paramount function that they perform. On each side, at the apical summit of the labium, are inserted the labial palpi. These are invariably four in number, but vary considerably in length and substance. In the Andrenidæ they have always the form of subclavate, robust joints, and are usually as long as the tongue, but not always; they are only half the length of that organ in the subsection of the acute-tongued Andrenidæ. In the normal bees, even in the genus Panurgus, which is the most closely allied to the Andrenidæ, the labial palpi immediately take excessive development, especially in their two basal joints, and the structure of these two joints, excepting in this genus and in Nomada, partakes of a flattened form and membranous substance. All these four joints are either conterminal, or the two apical ones, or one of them is articulated laterally, towards the apex of the preceding joint. These two are always very short joints, and are comparatively robust.

The labial palpi are, in the majority of cases, about half or two-thirds the length of the tongue, but in Apathus and Apis they are of its full length. At the immediate base of the tongue, and attached to it laterally, rather than to the apex of the labium, are the paraglossæ, or lingual appendages, which are membranous and acute, except in the Andrenidæ, where, in some, their apex is lacerated and fringed with short hairs. These organs are always present in the Andrenidæ and generally in the Apidæ, where they usually obtain extensive relative development; but in the artisan bees they are all but obsolete, and in Ceratina, Cælioxys, Apathus, and Apis, they are not even apparent. Their use also has hitherto eluded discovery, but that they are not essential to the honey-gathering instinct of the bee is especially proved by the latter instance.

The true tongue is attached to the centre of the apex of the labium, having the paraglossæ, when extant, and the labial palpi at its sides. In the Andrenidæ it is a flat short organ of varying form, either lobated, emarginate, acute, or lanceolate; but in the Apidæ, with Panurgus it immediately becomes very much elongated, and with this genus the apparatus whereby the tongue folds beneath obtains its immediate development; but this development exhibits itself most fully in the genus Anthophora. The tongue is usually linear, tapering slightly to its extremity, and terminating in some genera with a small knob. It is clothed throughout with a very delicate pubescence, which enables the bee to gather up the nectar it laps. That it should be called the lip seems an absurdity, for it exercises all the functions of a tongue, and it would seem almost that the fine hairs, with which it is covered, are the papillæ of taste. Its structure in some genera seems to be a spiral thread twining closely round and round, but in others it appears throughout identical.

Fig. 8.—Extremes of structure of tongues:
1, in subnormal bees (Colletes);
2, in normal bees (Anthophora).
a, tongue;
b, paraglossæ;
c, labial palpi;
d, maxillæ;
e, maxillary palpi;
f, labium.

This tongue was formerly thought to be tubular, and that the bee sucked the honey through an aperture at its apex. The knowledge of the flat form of the tongues of other bees should have dissipated the illusion, for we could have been perfectly sure of the analogical structure and function of an organ in creatures so nearly alike. Réaumur’s patient observations have totally dissipated the mistake, and through him we exactly know how the bee conveys the honey into its stomach As it exhibits an agreeable instance of the persevering industry and unblenching patience with which he made his researches, I will give a summary of what he says, for his bulky volumes, although teeming with delightful instruction, pleasantly narrated, will necessarily not be in every entomologist’s hand, and where not, not even always readily accessible. His observations were made upon the honey-bee, but we may attribute the same mode of collecting to all the rest. He says:—When this tongue is not lapping the nectar of flowers but in a state of perfect repose it is flattened. It is then at least three times broader than thick, but its edges are rounded. It gradually narrows from its base to its extremity. It terminates in a slight inflation, almost cylindrical, at the end of which there is a little knob, which appears perforated in the centre. From the circumference of this knob tolerably long hairs radiate, and the upper side of the tongue is also entirely covered with hairs. The basal and widest portion above seems striated transversely with minute lines closely approaching each other.

The upper side of the anterior portion of the tongue seems of a cartilaginous substance, but the under side of the same part appears cartilaginous only over a portion of its width. The centre is throughout its whole course more transparent than the rest, and seems membranous and folded. It is only necessary to press the posterior portion of this trunk, whilst holding its anterior part closely to a light, towards which its upper surface must be turned, and then upon examining its inner surface with a lens of high power, a drop of liquid may be soon observed at its foremost portion. By continuing to press it this drop is urged forward, and as it passes every portion swells considerably, and the two edges separate more widely from each other. The under side of the tongue, which was before flat, rises and swells considerably, and all that thus rises up is evidently membranous. It looks like a long vessel of the most transparent material. But whilst this great increase of bulk is made upon the lower surface, the upper surface swells only a little, which seems to prove that its immediate envelope is not capable of much distension.