Essays on the Microscope / Containing a Practical Description of the Most Improved Microscopes, a General History of Insects, etc., etc.

by George Adams

The proboscis is partly membranaceous, and partly of a gristly nature; the lower part is formed in such a manner, that it will swell out considerably, by which means the internal cavity may be prodigiously enlarged, and rendered capable of receiving a very large quantity of native and undigested honey, and larger than might be expected from its size. When the proboscis is shut up and inactive, it is very much flattened, and is three or four times broader than it is thick. The edges are always round; it grows tapering, though very gradually, towards the extremity. The lower and membranaceous part of the trunk has no fibres or villi on it, but is covered with little protuberant transparent pimples, that are placed in regular order, and at equal distances from each other, resembling the little risings observable on the skin of birds when the feathers have been plucked off. They are probably glandules, and may have a considerable share in changing or preparing the honey that is swallowed or taken up by the proboscis. Down the middle of the proboscis there is a tube of a much harder nature than the sides, it grows gradually smaller towards the top; at this place the tongue itself is extremely villous, having some very long villi at the point; whether they are open tubes, or whether they only serve as so many claws, to keep it in its proper place while in action, has not been determined; Mr. John Hunter conceives them to act somewhat like capillary tubes.

The proboscis terminates in a small cylinder c, at the top of which there is a little globule or nipple; the bee can contract this cylindrical part, and the little membrane in which the villi are fixed, into a much smaller compass, and draw it inwards. The exterior sheaths lap over each other on the upper part, so that the outside of the proboscis is protected by a very strong double case, a covering that was unnecessary for the under part; because when this instrument is in use the sheaths are opened, but when it is inactive, it is so folded that the under part is protected by the body of the bee. Withinside the exterior sheath, and near the bottom q, are two levers, which are fixed to the end of the proboscis, and by which it is raised and lowered.

Swammerdam thinks that the honey is, as it were, pumped or sucked up by the bee through the hole at the end b of the tongue; he does not seem to have discovered the apertures which are on the cylindrical part, near the end b. But Reaumur is of opinion that it is used to lap up the fluid, which is then conveyed down between the sheath to the mouth of the bee. To ascertain this, he placed a bee in a glass tube, the inside of which was rubbed over with honey, and little pieces thereof placed in different parts; the bee placed the tongue on the honey; stretching the end beyond the piece thereof, she bent it into the form of a bow, and inserted the most convex part of the bow into the honey; by rubbing the glass backwards and forwards with this part, she soon cleaned that portion to which it was applied, conveying the honey afterwards to the throat by the vermicular motion of the tongue.

If you attentively observe a bee, when it has placed itself on a full-blown flower, the activity and address with which it uses this apparatus will be very conspicuous. It lengthens the end, and applies it to the bottom of the petals or leaves of the flower, moving it continually in a vast variety of different directions; lengthening and shortening, bending and turning it in every possible way, to adapt it to the form, &c. of the leaves of the flower. These various movements are executed with a promptitude that surpasses all description.

The whole of this curious apparatus can be folded up into a very small compass under the head and neck. The larynx, or that part next to the head, falls back into the neck, which brings the extreme end of the first portion of the proboscis within the upper lip, or behind the two teeth; then the whole of the second part is bent down upon and under the first part, and the two last sheaths or scales are also bent down over the whole; so that the true tongue is inclosed laterally by the two second horny sheaths, and over the whole lie the two first.

OF THE PROBOSCIS OF THE BUTTERFLY.

From the tongue of the bee, let us now direct our attention to that of the butterfly. This is a spiral substance, somewhat resembling the spring of a watch when wound up, consisting of eight rounds; by means of a pin you may gently pull it out to its full length; it grows gradually tapering from the base, at the end it divides or separates into two tubes, each furnished with little organs of suction; probably, it is by these that it extracts the juices on which it feeds, and not by the extreme ends of the tongue. As the butterfly has no mouth, the proboscis is the only alimentary organ; when separated from the insect, it will often unroll itself, then wind and coil itself up again, continuing these motions at intervals for a considerable time.

OF THE PROBOSCIS OF THE CULEX OR GNAT.

The proboscis of the gnat consists of a great number of extremely delicate pieces, all concurring to one purpose; this is the instrument with which it strikes the flesh, and sucks the blood of animal bodies. The only part exhibited to the naked eye is the sheath, which contains all the other pieces. This sheath is a cylindrical tube, which is slit in such a manner, that the insect can separate it from the dart, and bend it more or less in proportion as the dart is plunged into the wound. From this tube the sting is darted, which consists of five or six blades or lancets of exquisite minuteness, lying one over the other; some of these are sharpened like a two-edged sword, while others are dentated and barbed at their extremities like the head of an arrow. The instant the gnat lances this bundle of darts into the flesh, and penetrates a vein, a drop or two of fluid is by it insinuated into the wound, by which the blood is attenuated, and the blades acting as so many capillary tubes, the blood ascends in them, and is conveyed into the body of the gnat. The injected fluid also by its fermentation causes that disagreeable and teazing sensation of itching, to which most persons are subjected, after having sustained an attack from one or more of these little animals.[52]

[52] To some persons the gnat (culex pipiens) is so truly formidable, that, during the Summer season, they constantly dread the approach of evening, that being the time when these blood-thirsty marauders sally forth in great numbers, pursue them wherever they go, and exempt no part of the face, hands, or even the legs from their depredations; the consequences of which are, violent, though happily only local and temporary inflammation, attended with insupportable itching, succeeded by tumors very similar to those occasioned by a scald; when these have discharged the pellucid fluid they contain, the symptoms subside. Instances have been known in the vicinity of London, where for several days the eyes of the sufferers have been closed, the nose and lips violently swelled, the fingers of both hands so affected as to prevent their motion, and the legs equally affected. It is remarkable, that in general those who thus suffer are not conscious of the moment when they receive the injury, but are soon made sensible of it by the effect it produces. The approach of the enemy is, however, always known by the singing or humming noise they make; the peculiar note of which, though rendered very familiar by daily repetition, is never esteemed sufficiently musical to render it pleasant or agreeable to the destined victims. Amongst the variety of remedies which have been recommended for the cure of this temporary evil, Barbut mentions the immediate application of volatile alkali, or scratching the part newly stung, and washing it with cold water; he likewise asserts, that rubbing the part at night with fuller’s earth and water abates the inflammation. As preventives are certainly more acceptable than curatives, I wish I were enabled to recommend such in the present case: in one instance, the application of vinegar every evening before sun-set produced a happy effect; possibly washing the parts exposed with extract of saturn properly diluted might prove effectual.