Popular Science Monthly/Volume 14/March 1879/The Sting of the Honey-Bee
|THE STING OF THE HONEY-BEE.|
PERHAPS there is no object more common in the cabinets of microscopists than mounted specimens of bee-stings. Almost every popular work on the microscope describes and figures them, but it is only within a few months that the true structure of these organs has been made known. Mr. J. D. Hyatt, of this city, has been studying the subject for the past eight years, and his recent discoveries have shown that the ordinary descriptions are incorrect and founded upon mere inferences, drawn from the appearance of the organ as usually dissected and mounted. There are no less than eight discoveries, for which we are indebted to the labors of this gentleman, and it is our intention to present some of these as briefly as possible.
By reference to the cuts the following descriptions will be made clear: Fig. 1 represents the entire apparatus of the sting of the honeybee, with the muscles removed, showing only the hard parts and the poison-gland (P). The lancets (K K) are drawn out from their natural position to show their structure more clearly. The sting is usually described as having two barbed lancets (K K) which move in and out of the "sheath" (D), the inner sides of the lancets being channeled, so that when they are thrust out together they form a tube through which the poison enters the wound. It appears, however, that the so-called "sheath" does not inclose the lancets in any part, and therefore is not a sheath, as formerly supposed. Moreover, while the virus may, and undoubtedly does, pass along the tubular space between the lancets, this is not the course it follows to reach the bottom of the wound. A far more elaborate arrangement, a sort of miniature hydraulic ram, forces the fluid through the lancets themselves, and this is one of the most recent discoveries. By examining the lancets with a rather high power, it will be seen that each appears to be tubular, and that the tube runs down nearly to the apex, but always disappears before reaching the end. From this main tube, and just back of each of the last five teeth, we notice fine branch-tubes which open on the surface between them. All this is well shown in Fig. 2, the branch-tubes opening at the points b b b b b. This figure represents the lower part of one of the lancets, showing the shape of the barbs and the extremely sharp point. The lancet is thus seen with a power of four hundred and fifty diameters; the point of the finest sewing-needle magnified to the same extent would appear as blunt as the end of a crowbar. Although the tubular appearance was evident to any one who looked for it, the next step was to prove that the lancets were in truth hollow, for it is not safe to rely upon mere appearances when using the microscope. Mr. Hyatt succeeded in proving their tubular nature in several ways: he succeeded in forcing liquid through them, first by a little delicate manipulation, and finally by cutting thin transverse sections and mounting them so as to view them on end. One of these sections, which shows the form of the lancet and the tubular opening passing through it, is shown at e, Fig. 3.
Following the lancet from the apex toward the larger end we pass the gracefully curved barbs to a smooth portion, and then reach a curious projection (Fig. l,p), firmly braced and attached to the lancet as seen in the figure. When in the natural position these projections lie within the "sheath" (D). These are known as the stop-valves. The tubes of the lancets terminate just back of where the stop-valves are attached, here opening into the cylindrical portion of the "sheath."
We pass now from the lancets to the "sheath" (Fig. 1, D), The general shape is well shown in the figure. The cylindrical portion (D) suddenly contracts, forming a shoulder at d, and a slender portion extends for some distance beyond. Along the straight edge the lancets run in the manner shown in Fig, 3. In this figure the darker portion (n) represents a cross-section of the "sheath," the two lighter pieces (b and d) are cross-sections of the lancets, one (d) in situ. Running the entire length of the "sheath" we find the T-rail projections (g g) along which the lancets slide, being channeled to fit, as seen at b, Fig. 3. Thus we see that the main "sheath" is not a proper term for this part of the apparatus, for the lancets are entirely outside of it and run along the rails. The poison-gland (P) empties into the cylindrical part of the sheath, and keeps it constantly full of virus, at least when the bee is excited. A, B, and C, are broad chitinous pieces, to which muscles are attached. They form a peculiar combination of levers, too complicated in their action to be described here in detail, but they serve to thrust out the "sheath" and the lancets, giving to the former a powerful thrust, and to the latter a movement of great rapidity.
We are now prepared to understand the operation of stinging. The two lancets (K K) when in position lie close against the "sheath," as already described, and their ends reach just to the point of the latter. When the insect stings, the palpi (E E), which are drawn away from their proper place in the figure, serve to direct the organ to the most vulnerable point of attack. Then, with a sudden, powerful motion, the "sheath" is forced out and produces the puncture, penetrating as far as the point d, where the expansion begins. Instantly the two lancets are then forced out together, increasing the depth of the wound made by the "sheath." It has generally been supposed that the lancets were the organs that made the puncture, but this is not the fact. The lancets are thrust out until the stop-valves (p p) strike against the shoulder d (Fig. 1). This closes the cylindrical part of the sheath, which is full of virus, and this virus, being under pressure either from the sudden stoppage of the free outlet by the stop-valves or the contractions of the poison-gland (P), or both these causes combined, makes its way into the tubular lancets through the openings already mentioned just back of the stop-valves, and enters the wound through the branch-tubes b b b b b (Fig. 2). Thus we see that the injection of the poison into the wound is fairly comparable to the working of an hydraulic ram.
When the honey-bee stings, it is well known that the sting is not withdrawn from the wound. The sharp barbs on the lancets make it impossible for the bee to withdraw them, but more than these may be left behind. By allowing the insect to sting a piece of soft leather, not only the lancets but also the sheath and poison-gland will be beautifully dissected out, the bee apparently not suffering from their loss.
It will be seen that the lancets are curved at their attachment with the levers which move them. This curved portion is flexible, while the points are brittle. The poison-gland is provided with a muscular coat. It has been previously supposed that the virus was expelled from the gland by the pressure of other parts. There are several interesting points connected with the mechanism of the sting, which have been omitted here on account of the detailed description that would be required to make them intelligible.
Naturalists should not be slow to appreciate the conscientious labor which alone has led Mr. Hyatt to these results, or to follow up the line of investigation which he has opened.
- Abstract from a paper, by J. D. Hyatt, in the "American Quarterly Microscopical Journal," October, 1878.