If a bee be observed whilst sipping any sweet liquor, the anterior portion of its trunk will be sometimes seen more swollen than when in action, and alternations will be observed in it of varying expansion.
The posterior portion of the trunk is a great deal larger than the anterior, and it is only in repose that the former nearly equals the latter in length. This posterior portion (this is the portion treated above as the labium, or under lip) is joined to the anterior by a very short ligature, wholly fleshy, and very flexible, which permits the folding of the trunk, and then its under side is quite scaly, very shiny, and rounded (the maxillæ). This portion is apparently more substantial than the rest. Its diameter gradually increases as it recedes from about the middle to about two-thirds of its length; there it is a little constricted, and the first of the two pieces of which it is composed there terminates. The first piece is rounded, for the purpose, it would appear, of fitting itself upon another, which serves as its base and pivot. This base is conical and of a scaly texture, and terminates in rather an acute point. It is this point which is articulated at the junction of the two small elongate portions of which we spoke at the commencement, and which carry the trunk forward.
In repose, the posterior part of the trunk lies along the lower part of the mouth, and the anterior part is folded back upon it, when it is covered by the maxillæ, which then seem to form a portion of it. It has further another interior envelope; these are the two first joints of the labial palpi (in the Apidæ), which are entirely membranous, and these in repose cling closely to the tongue laterally.
The bee would certainly not collect its honey differently from a flower than it would from a glass wherein it might be placed to observe the process; and here it never appeared to obtain the honey by suction. The bee was never observed to place the end of its tongue in the drop of syrup, as it would necessarily do if it were requisite to imbibe it through what seems the small aperture at the extremity of the knob, at the end of the tongue, previously described. As soon as the bee finds itself near the spot spread with honey or syrup, it extends its tongue a line or so beyond the end of the palpi, which continue to envelope it throughout the rest of its length. If the honey be spread over the glass, the anterior portion of the tongue, which is exposed, is turned round that its superior surface may be applied to the glass. There this portion does precisely what the tongue of any animal would do in lapping a liquid. This tongue repeatedly rubs the glass, and, moving about with astonishing rapidity, it makes hundreds of different inflexions.
If the drop of syrup presented to the bee be thicker, or if it meet with a drop of honey, it then thrusts the anterior portion of its tongue into the liquid, but apparently only to use it as a dog might do its tongue in lapping milk or water. Even in the drop of honey the bee bends the end of its tongue about, and lengthens and shortens it successively, and, indeed, withdraws it from moment to moment. We then observe it not merely lengthen and shorten this end, but it is also seen to curve it about, causing from time to time the superior surface to become concave,—to give, as it were, to the liquid with which it is loaded a downward inclination towards the head. In fact, this portion of the trunk appears to act as a tongue, and not as a pump. Indeed its extremity, where the aperture for receiving the liquid is assumed to be, is repeatedly above the surface of the liquid which the insect is lapping.
By these continuous motions this anterior extremity of the tongue charges itself with the nectareous fluid, and conveys it to the mouth. It is along the upper surface of this pilose tongue that the liquid passes. The bee strives especially to load and cover it with honey. In shortening the tongue to the extent, sometimes, of withdrawing it entirely beneath its sheaths, it conveys and deposits the liquid with which it is charged within a sort of channel, formed by the upper surface of the tongue and the sheaths which fold over it. Thus, these sheaths are, perhaps, less for the purpose of covering the tongue than to form and cover the channel by which the liquid is conveyed to the mouth. I have previously remarked that the trunk can swell and contract; these swellings and constrictions are observed to succeed each other, and may be for the purpose of urging the liquid, already in transit beneath the sheaths, forward towards the true mouth. Further, I moved the sheaths aside from their position above the tongue of a bee which I held in my fingers, and I succeeded, by means of the point of a pin, in placing an extremely small drop of honey upon the tongue of this bee at a spot where it could be covered by the extremities of the external sheath. I then let these sheaths loose. Sometimes they spontaneously resumed their previous position, and sometimes I assisted them to resume it. The drop of honey which they then covered has in no instance returned to the extremity of the tongue; it has always passed towards the mouth, and doubtless entered that orifice itself. It is therefore very certain that the bee imbibes its honey by lapping, and that it never passes through the aperture which has been supposed to have been seen at the extreme apex of the tongue. Did this aperture really exist, it would be of extreme minuteness, and it did not appear to me possible that a large drop of honey, which I have seen imbibed in a very few instants, could in so short a time have passed by so minute an opening. A further confirmation of the non-existence of this orifice has been given me when, by pressing a tongue towards its origin to compel it to swell, I have detected the liquid which gave it its extension, but all my pressing would never make the liquid pass through the extremity, although the pressure has sometimes made it almost rend the membranes, to give it an opening to escape by. Having thus passed through the œsophagus into the stomach, it is then regurgitated into its requisite repository upon arriving at home.
Andrenidæ
Apidæ.
Fig. 9.—Mode of folding the tongue in repose.
1. In abnormal bee.
2. In normal bee.
a, point of articulation beneath the hypopharynx:
b, apex of the tongue.
The entire proboscis, with all its appendages attached, has in the Apidæ three distinct hinges or articulations, including that which attaches it by its extreme base to the under surface of the mouth and lower portion of the head, the cavity of which, when folded, it fills, and even then the apex of the tongue protrudes in some genera beyond the sheathing maxillæ. In the Andrenidæ it has but two articulations, and the maxillæ always cover them entirely in repose. The first articulation, forming the fulcrum of the whole, is always elbowed in the Apidæ, and consequently not capable, like the rest of the joints, of full linear extension. The attached diagram will give a clearer conception of the mode of folding: a is the labium, and b the tongue.