to widen and deepen the course, after the iiner points have pioneered the way.

The merry little jumping insects called Frog-hoppers (Tettigonia), one of which in its larva state emits the little mass of froth so common on shrubs, and called cuckoo-spit, are furnished with a set of tools for their own private carpentry, which, though less elaborate than those of the saw-flies, are worthy of a moment's glance. If we catch one of these vaulters, and gently press the abdomen, we shall see proceeding from its hinder and lower part a thickish piece, large compared with the size of the insect, which it is then easy to extract with a pair of fine-pointed pliers. I have just done this, and here is the result on a slip of glass.

First, there is a pair of brown protecting pieces, oblong in form, and studded with hairs like the rest of the exterior of the body. From between them projects what resembles a lancet, of the usual translucent ambercoloured horn, appropriated to these instruments (which is to them what steel is to us) ; and this we shall presently discover to be composed of two blades exactly alike, convex without and concave within, applied face to face. One edge of this pair of implements is quite smooth, but the other is cut into the most beautifully regular and most minute teeth.

This, however, is but the sheath. Within the two spoon-shaped faces there lie two other lancets, blade to blade, still finer and more delicate. Both edges of these blades are of the most perfect keenness, without a flaw; but their sides appear roughened with rows of very minute horny knobs, like a rasp.

I shall illustrate this demonstration by another extract from Reaumur, premising, however, that his observations refer to the large species of true Cicadce from warmer latitudes, whose machinery seems to differ from that of our little friends in some particulars. For example, the two inner lancets seem to be united in one, in Reaumur's species, or else, which I think more probable, he did not succeed in separating them.

He describes the two curved spoon-shaped pieces as finely indented on both sides with teeth, which are strong, nine in number, arranged with great symmetry, increasing in fineness towards the point. This instrument he describes as composed of three pieces, the two exterior, which he calls the files, and another pointed, which he compares to a lancet, which is not toothed. "The files are capable of being moved forward and backward, while the central one remains stationary ; and as this motion can be effected by pressing a pin or the blade of a knife over the muscles on either side at the origin of the ovipositor, it may be presumed that those muscles are destined for producing similar movements when the insect requires them. By means of a finely-pointed pin carefully introduced between the pieces, and pushed very gently downwards, they may be, with no great difficulty, separated in their whole extent.

" The contrivances by which those three pieces are held united, while at the same time the two files can be easily put in motion, are similar to some of our own mechanical inventions, with this difference, that no human workman could construct an instrument of this description so small, fine, exquisitely polished, and fitting so exactly. We should have been apt to form the grooves in the C9ntral piece, whereas they are scooped out in the handles of the files, and play upon two projecting ridges in the central piece, by which means this is rendered stronger. M. Reaumur discovered that the best manner of showing the play of this extraordinary instrument is to cut it off with a pair of scissors near its origin, and then, taking it between the thumb and the finger at the point of section, work it gently to put the files in motion.

" Beside the muscles necessary for the movement of the files, the handle of each is terminated by a curve of the same hard horny substance as itself; which not only furnishes the muscles with a sort of lever, but serves to press, as with a spring, the two files close to the central piece. *

The use of these instruments is the same as I have already alluded to in the case of the saw-flies. The female Tree-hopper deposits her eggs in holes, which she bores in dead twigs by means of these files and lancets. The branches chosen are said to be easily known by being studded with little oblong elevations, caused by the partial raising of a splinter of wood at the orifice of the hole, to which it serves as a cover. These are arranged in a single line ; the holes which they protect being only half-an-inch in length, and reaching to the pith, whose course they then follow. Not more than six or eight eggs are laid in each hole ; but an idea of the labours of the industrious and provident mother will be formed from the fact that she lays six or seven hundred eggs in the course of the summer. * "Insect Architecture," 149.

Chapter IX. Insects: their Mouths

The parts of the mouth in different Insects afford an almost endless store of delightful observations ; and the more as, with all their variety, they are found to be in every case composed of the same essential elements. You would not think so, indeed ; you would naturally suppose—looking at the biting jaws of a Beetle, the piercing proboscis of a Bug, the long, elegantly-coiled sucker of a Butterfly, the licking tongue of a Bee, the cutting lancets of a Horse-fly, and the stinging tube of a Gnat—that each of these organs was composed on a plan of its own, and that no common structure could exist in instruments so diverse. But it is so, as we shall see.

We may consider the various organs of the mouth as most harmoniously and perfectly developed in the active carnivorous Beetles ; the Carahidce, or groundbeetles, for instance. Let us examine the head of this black Scarites from the garden ; and first from above.

In front of the polished head-shield, and jointed to it by a broad transverse straight edge, is a four-sided piece, forming an oblong figure, nearly twice as broad as long, a little convex, and marked with six little pits or sinkings of the surface, along its front edge. This is the upper lip; but, instead of being fleshy, as ours is, it is composed of a hard polished black shelly substance, of a peculiar insects: their mouths. nature, called cliitine, the same substance as the hard parts of all Insects and Crustacea are made of.

From beneath the sides of this there project on each side two broad hooked pieces, which, as you see, I can with a needle force out laterally, so as to show their form better, for they hinge upon the sides of the face, beneath the head-shield. Each forms the half of a crescent, the curved points of which are turned towards each other, and can work upon each other, the points crossing like shears. These are the proper biting jaws, or mandibles, and in many of the larger beetles they have great power of holding and crushing. Sometimes their inner side is cut into strong teeth, but here this side forms a blunt cutting edge ; the upper surface, however, is scored with ridges and furrows like a file ; and this structure is best seen in the left jaw, which, when the pair close, crosses over the right. This is an action of the jaws the reverse of ours ; but it is characteristic of all articulate animals, in which the jaws, whenever present, always work horizontally, from right to left, and not vertically, up and down.

I will now, by making the forceps revolve, bring the under side of the head into view ; for, without separating the parts by dissection (which, however, is by no means difficult), it is impossible to see them all from one point of view. The part nearest our eye now is the chin, a wide horny piece, like the upper lip, jointed to the head by its straight hind edge, but, unlike it, having its front edge hollowed out with two deep notches, the central piece between them itself notched at its tip. Immediately above this notched central tooth (I speak of the relative position of the parts, supposing the insect to be crawling on the ground, without reference to the way in which we turn it about on the microscope), and united with it, there is a sort of solid square pedestal, on which stand a pair of jointed organs, and between them an oblong horny plate rounded at the tip, where it bears two bristles. This latter is the tongue, while the jointed organs on each side are called feelers,—palpi; though this is a begging of the question, for we do not really know the function of these organs. The chin, the tongue (ligula), and these palpi, constitute together the under lip.

Between the tongue and the biting jaws, or mandibles, we see a pair of organs similar to these latter, but smaller, less solid, and more curved. These are the under or secondary jaws, maxillce, the use of which is to hold the

MOUTH OF BEETLE.

{Seenfrom beneath.)

a, upper lip ; b, mandibles ; c, maxillae ; d, maxillary palpi ; e, tongue ; f, labial palpi ; g, chin. food, while the biting jaws work on it, and to convey it when masticated to the back of the mouth. Their whole inner edge is set with short stiff bristles, which towards the tips of the jaws become spines. Near the bases of these jaws, on the outer edge, are jointed two other pairs of palpi, one pair to each jaw ; of which the exterior is much stouter and longer than the interior. Thus this

beetle has three pairs of these many-jointed organs, viz., the labial, and the two pairs of maxillary palpi.

Now, in this form of mouth, which has been called a perfect or complete mouth,—that is, one in which all the constituent parts can be well made out, we find the following organs :— 1. the upper lip (labrum) ; 2. the mandibles; 3. the maxilla?; with o, the maxillary palpi; 4. the lower lip (labium), comprising /3, the tongue, y, the labial palpi, c, the chin (mentum).

I now exhibit to you the head of the Honey-bee. The front is occupied by an upper lip, and a pair of biting jaws (mandibles), which do not greatly differ from the same parts in a beetle. The jaws, however, are more hatchet-shaped, or rather like the hoof of a horse, supposing the soles to be the opposing surfaces. The other organs are greatly modified, so that you would scarcely recognise them. The under jaws (maxillce) are greatly lengthened ; and the two, when placed in contact, form a kind of imperfect tube or sheath. Within these is the lower lip, divided into its constituent parts : the thick opaque chin, at its basal end ; then the two labial palpi, each consisting of four joints, of which the two terminal ones are minute, while the two basal are large and greatly lengthened, so as to resemble in appearance the maxillce, whose function they imitate also ; for the pair of palpi when closed form an inner sheath for the tongue. Finally, you see this organ, which is the most curiously developed and modified of all, for it is drawn out to a long slender, cylindrical tube, formed of a multitude of close-set rings, and covered with fine hairs. Some deny it to be tubular, and maintain that it is solid ; but certainly it appears to me to have a distinct cavity throughout, with thickish walls.

Page 22 of 66