this paper because in some particulars it is different from the sting of any other insect that I have yet examined, though in its general features it may be taken as a type of the "terminal armor" in the whole order of Hymenoptera, for the difference between a sting and an ovipositor is more a difference of function than of structure.

It must be observed, however, that this difference is, of its kind, a very wide one, for the ovipositor is an apparatus of a perfect female for depositing the eggs, while in those insects furnished with a sting the female organs are so differentiated, aborted, or completely suppressed, as to render fertilization impossible, so that wherever this armor occurs, as it does mostly among social insects, it is confined to a class called neuters, or modified females.

The sting of the Honey Bee consists of a dark brown horny, chitinous piece, of a cylindrico-conical form, commonly called the sheath, which is cleft along its inferior surface, and terminates in an obtuse, but extremely thin cutting point. This is the chief instrument in effecting a puncture.

Fig. 5. Portion of a lancet showing valve, a e, much enlarged; h, truss holding the valve in place; X 450.

Fig. 6.* Section across sheath and lancets at the point where the valves are attached to the latter; 11, the lancets and appendages; n, space between the outer and inner walls which changes its form to n, in Figs. 7 to 9.

Fig. 7. Section of sheath and lancets, at the point opposite, with section of one lancet removed, to show the form of groove, b, and guide-bar, g.

Figs. 8 and 9. Section of sheath and lancet, with latter held in normal position by Trails, or guide bars on each side, g g; a, channel between the lancets for passage of poison into the wound.

Fig. 10. Showing mechanism of compound lever-moving lancet (one side only); b, arm of sheath detached; D, lever-moving sheath, its form bounded by the line, k, o, n, m; C, lever moving the triangular piece attached to lancet at c; change of position of the piece, C, to dotted line, projects broken end of lancet from a to a'.

Fig. 11. Point of one lancet, showing barbs and small canals, bbb bb, be tween the last five; X 450.

Fig. 12. Section of lancet immediately posterior to valve, showing its tubular form and the valve, d, which prevents leakage along the sides of the lancets in

contact.

Fig. 13. Point of sheath, showing thin convex end, and two lateral barbs; X 450.

*Figs. 6 to 9 were inverted by the engraver; the parts toward the top of the page are on the inferior side.

Lying along, and partly in the cleft of the sheath, are a pair of tubular darts or lancets, having a fine cutting edge curved to the inward side, while the lateral margins are serrated near the point with ten deep retrorse barbs. These lancets are capable of being projected beyond the sheath, so as to increase the depth of the wound made by that instrument.

A sac or reservoir is connected with the base of the sheath and discharges into it by the rapid contractions of its muscular coats, a poisonous fluid which is conducted into the wound through a channel between the concave faces of the lancets; the escape of this fluid between the outer (inferior) convex edges being prevented by a valve, consisting of a thin flange projecting inward from each.

A mechanism resembling the hydraulic ram is found in the cylindrical part of the sheath, which serves to inject the poison with great force through several small apertures, near the points of the tubular lancets, into the extreme limit of the wound to which they are projected.

The sheath and lancets are protruded, not by the direct action of the muscles, but in order to impart great penetrating force to the former, and a quick motion to the latter, they are actuated through a peculiar combination of levers, which is perhaps the most curious and interesting feature of the entire mechanism.

Finally, a pair of palpi, or feelers, are uniformly projected, in advance of a thrust made by the sting, to determine the most vulnerable point of attack.

This being the general plan of this apparatus, the details of its structure, and the particular function of each part, will be better understood by a reference to the drawings and diagrams, which are exact delineations of the objects presented, and very correct as regards the relative proportion of connected parts, though the different figures are not drawn to the same scale of amplification.

Fig. I presents a view as seen from the inferior side of all the pieces connected with the "terminal armor" of the Honey Bee, with the exception of the poison gland, only the excretory duct of which, P, is here seen.

The median, or more darkly shaded piece A, extending the entire length of the figure, and loosely enclosed by the vulva,

has commonly been called the sheath, because it was supposed to enclose, like a scabbard, the two darts or lancets.

The sheath, in this view, is conical in form; the base being anterior, directed toward the head of the insect, and its apex posterior.

A lateral view, however, Fig. 3 A, shows the anterior portion to be cylindrical, but contracting on the upper side opposite the point c, diminishes gradually to the extremity, near which are two lateral teeth seen in the greatly enlarged view, Fig. 13 b b.

The sheath is double throughout its whole extent. The exterior and interior walls, which, in a rudimentary state, form two separate pieces, are firmly united at their edges, and in the cylindrical portions of the sheath are nearly in juxtaposition, forming, in lateral view, the oblong valve-chamber A, Fig. 3, but the inner wall abruptly contracting at c, Fig. 3, leaves a lunate space above it, as shown in the transverse section at this point, Fig. 7 n. A cross section at the point P, Fig. 3, is seen in Fig. 6. Between the walls at this point, and also throughout the entire cylindrical portion, there is an enclosed space shown at n, Fig. 6. At the point c, Fig. 3, where the contraction is seen, the space n begins to alter its form, and this alteration continues down to the apex, where the two walls unite. Several successive stages of this alteration are shown in Figs. 7 to 9 at n. It will thus be seen that n, Fig. 7, is a continuation of the smaller space n in Fig. 6.

It will be observed that n, Fig. 7, has no connection with a, Fig. 6, so that the poison injected into the cylindrical base of the sheath follows the channel a, Figs. 7 to 9, between the lancets.

Near the base of the sheath, on the inferior side, arise two flexible arms, b b, Fig. 1, which curve in arcs of a circle in a lateral and dorsal direction to their articulations e e, with the powerful levers D D.

The cylindrical part of the sheath is cleft along the lower side, and this cleft, taking the form of a shallow groove, continues to the end.

Lying in contact, in this groove, and along the inner margins of the cleft, are the two lancets, their barbed edges k k extending laterally over its sides, and following the curve of the arms before mentioned, are attached at c c, their anterior ex

tremities, to the triangular pieces B B of the compound levers, composed on each side of the two pieces, B and C.

From the point p, Fig. 3, along their straight parts, the lancets are tubular, taking the form e seen in the section, Fig. 7, their incurved edges lying in contact in the groove of the sheath, Figs. 8 and 9, and forming a circular channel, a, between them, through which the poison is injected. Projecting into the channel a are seen the valves (one at d, Fig. 7), which, falling together, prevent the escape of the virus along the outer sides of contact.*

Along the inner margins of the groove, on each side and following the curved arms of the sheath, are two T shaped rails, Fig. 7 a, or guide-bars, which, exactly fitting into grooves of similar form, Fig. 7 b, in the lancets, hold them firmly to the sheath, and at the same time allow a free sliding motion for their projection.

Between each of the last fine teeth of the lancets is a small canal extending outward from the central cavity, rather indistinctly seen at b b b b b, Fig. 11, which presents a very correct view of this part as shown under the microscope.

The extent to which the lancets may be projected is limited by the stop attached to each at p, Fig. 3, and extending nearly across this cylindrical part of the sheath.

The protrusion being arrested at the angle c, Fig. 3, formed by the sudden contraction of the sheath at that point.

This appendage also acts as a valve to check the flow of poison through the channel between the lancets, as may be seen by observing its structure in the greatly enlarged lateral view, Fig. 5, and in the transverse section through both lancets and sheath, Fig. 6.

It consists of two nearly semi-circular pieces, Fig. 5, a e, attached at their inferior angle to the lancet, the straight sides being anterior. On this side, each piece is thick and chitinous, but diminishes to a thin, flexible edge on the curved side.

Both pieces are firmly braced and held in place by the heavy curved piece b, extending from the straight side of both to its solid attachment with the lancet.

A section through the point at which the two pieces forming this valve are attached, Fig. 6, shows an opening between them

* By an unfortunate misunderstanding, Figs. 6 to 9 were inverted by the engraver.

to the interior cavity of the lancets, through which the poison enters the moment this valve closes the channel between the lancets by striking into the angle of the sheath at c, Fig. 3.

By the sudden closing of this valve, an action comparable to that of the hydraulic ram ensues, for the fluid virus, poured into the wound at first through a comparatively large outlet, is suddenly arrested in its course, and if it may be supposed to have any momentum, will be injected with increased force into the deeper wound made by the protrusion of the lancets, passing out of them through the minute canals seen in Fig. 11, between the barbs. This comparison, however, in the case of the bee, ends with a single stroke; for the sting is so firmly anchored, by the deep, recurved teeth, that in most cases it cannot be withdrawn, and the insect escapes leaving it in the wound.

By allowing the bee to sting a soft piece of leather, an excellent opportunity is thus offered for studying certain parts of the action and mechanism, for the whole apparatus, including the poison gland, or the entire parts, with this addition, seen in Fig. 1, will be beautifully dissected; the bee not appearing to be seriously injured by the loss. Rapid automatic contractions of the muscular coats of the poison-gland continue to pump out its venomous contents, and the muscles attached to the broad lever, C, make ineffectual efforts to retract the lancets for several minutes after the parts have been detached from the body. These motions can easily be seen without a lens.

The lever mechanism, which enables the bee to thrust its weapon, nearly the entire length, beyond the abdomen, with a penetrating force, apparently so disproportionate to its size and strength, will be readily understood by reference to Fig. 1.

The pieces, C and D, furnish broad surfaces of attachment to the muscles, with which their upper (inner) superfices are closely packed. These muscles extend in groups forward to the sternites or lower segments of the abdomen. The points, D D, being fixed by a pair of ligaments connected with the segment above.

By the contraction of the attached muscles, all the pieces, C, D, and B, on both sides, are swept together around the