cliffs that border the sea-shore may often be found some wingless but active Insects, which are endowed with the power of leaping in great perfection. From their hinder extremity being furnished with long projecting bristles, they are sometimes called Bristle-tails, but naturalists designate the genus Jfachilis. If you can get one sufficiently still to examine it, you will be delighted with the lustre of its clothing, which appears dusted all over with a metallic powder of rich colours,—red, brown, orange and yellow, foiled by dull lead-grey in places.

EBISTLE-TAIL.

(Slightly enlarged.)

If you touch one of these nimble leapers, though ever so lightly, you will see the result on your linger-ends ; for they will be found covered with a thin stratum of the finest dust, which displays the coloured metallic reflections seen on the insect. By touching one with a plate of glass instead of your linger, you will get the same dust to adhere to this transparent medium, by applying which to the microscope you may at once discern the marvellous nature of the raiment with which the little creature is bedecked.

The dust is now seen to be composed of myriads of thin scales, mostly regular and symmetrical in their forms, though varying exceedingly among themselves in this respect. Some are heart-shaped, some shovel-shaped, some round, oval, elliptical, half-round, half-elliptical, long and

narrow, sometimes irregular and unequal, and of various other indescribable outlines. Perhaps the most common forms are ovate, heart-shaped, and like that of the pan of a fire-shovel. Each thin scale has a minute foot-stalk y which is not connected with it at either extremity, but at a point of one surface a little way from the smaller end, whence it projects at an oblique angle ; so that when the stalk was inserted in its proper cell in the skin of the insect, the scale lay horizontally, covering the insertion. This is a peculiarity not found in some other scales that I shall presently introduce to you.

The whole body of the scale is traversed by a series of fine closeset parallel lines, running longitudinally from end to end. At least this is the ordinary arrangement ; but occasionally you see scales, in which there are two series of parallel lines, arranged on either side of an imaginary central line,towards which they respectively converge,but never SCALE OF BRISTLE-TAIL. I think, diverge from it. These lines appear to form thickened ribs, but seem to be made by elevations of the membrane both above and below. Between the ribs, on the larger scales, we see a number of very delicate cross lines, which are probably regular wrinklings of the depressed surface.

There is another little Insect of the same family, commonly found in cupboards, and in chinks of old damp houses, and called the Sugar-louse (Lepisma); very much like this, but of a silvery lustre, and carrying the three bristles of the tail diverging widely. This also is covered with scales, some of which are preserved on this glass slide. Here, while the general appearance and structure agree with those of the scales which we have just been

considering, there is considerable diversity in details. The form is usually ovate or shovel-like ; the foot-stalk, projecting at a similar angle, is not set on the inferior surface, but in the bottom of a deep narrow incision ; and the ribs are invariably divergent like those of a fan. In these, however, there is a peculiarity of arrangement, which I have never seen noticed, but which is obvious enough in the specimens before us. The ribs on the two surfaces diverge at different angles, those of the upper surface being the more divergent, standing out widely from the foot-stalk, while those of the lower membrane are coarser, and much more nearly parallel, their bases ranging along the hind edge of the scale. The effect of the intersection of the sets of lines at so acute an angle, is to convey the optical impression that the scale is covered with short irregular dashes.

Such is the arrangement on these scales, which I prepared myself from the common Lepisma; but I have a slide marked " Lepisma," from one of the dealers in microscopic objects, in which the ribs on the two sides concur ; but, on one side, there are obliquely divergent lines visible only near the margin, which appear to be produced by wrinkles of the membrane analogous to the transverse dashes on those of Machilis.

Scales much more delicate than either of these sorts are found on the Podura, a minute insect, of which there are several species ; which leap, jerking out the bristles of the tail, that are ordinarily carried under the body, like a coiled spring. They are common in cellars, in hot-bed frames, on dunghills, on the surface of water in roadruts, kc. On the slide before you are some of the smaller scales from one of these insects ; they are exceedingly delicate, and the clearness with which you discern the character of their markings, is a proof of the good definition of your microscope; this is what is called a "testobject." At first sight they seem covered with ribs like those of the Machilis and Lepisma ; but, by the use of a magnifying power of 600 diameters (as I have now put on), you perceive that, in the first place, the lines are not straight nor parallel, but curve irregularly, and are often branched; and, in the second place, that they are not uninterrupted, but made up of a series of successive wedge-shaped warts, which lie nearly flat, but project a little at the larger end, where each overlaps the next.* The scale we are looking at measures "00 14: inch in length, and '0009 in width; here the marks are well defined; here are smaller scales *0008 in length by -00035 in width, but these are more dim and difficult to resolve.

The beautiful and extensive order called Lepidoptera or Scale-winged, par excellence, including the gay tribes of Butterflies and Moths, present us with many exceedingly interesting varieties in these singular coverings. The study of these might be almost as wide as the immensity of species; I can show you only a few examples.

Here are specimens from the pretty little white Fiveplume Moth (Pterophorus), so common in meadows in summer. The general shape of the scales from the body and wings is that of a willow-leaf, some singly pointed, but more cut at the tip into two, three, or four notches. Those from the legs are longer, and slenderer in proportion; and among the others from the wings, there are some which take the form of hairs, which send forth one or more branches from one side, that form a very acute angle with the main stem. The scales proper are all

Mr. Richard Beck, using illumination under a power of 1,300 diameters, with the binocular microscope, has satisfied himself that the markings of the Podura scale " consist of a series of toothed ridges, the profile of which might be said to resemble the edge of a saw." He believes that the markings on this and all similar scales are " more or less elevations or corrugations upon the surface, which serve the simple purpose of giving strength to very delicate membranes." (See Quart. Journ. Microsc. Sci. for 1862, p. 122.) This verdict, though diverselyexpressed, does not importantly differ from my own judgment given above.

marked "with longitudinal lines, very minute and close, but they mostly bear a central band, and sometimes a marginal one on each side, of spots set in sinuous lines like the bands on a mackerel's back ; these are probably composed of pigment-granules.

These from the pretty Six-spot Burnet Hawk-moth, are nearly opaque, especially those from the red parts of the wings, which have a rich ruddy glow by transmitted light- They are narrow in shape, tapering gradually forward from the foot-stalk, and terminate mostly in two blunt points. The ribs are coarse for the size of the scales, and the depressed spaces are marked with irregular pigment grains.

The hairs with which the bodies of Moths are invested are essentially of the same character as the scales which clothe their wings. Here are examples from the glowingsides of the abdomen of that richly coloured insect, the Cream-spot Tiger-moth (Arctia villica). You see they are simple scales, drawn out to an inordinate length and great tenuity; each has its quill-like footstalk, and we may trace on some of them the ribs and transverse dotting, while here we see all intermediate stages between the slenderest hair and the broadly ovate, bluntly pointed, scales from the wings. You are familiar of course with the brilliant little Blue Butterfly (Polyommatus Alexis), which dances and glitters in the sunshine on waste places in June. Among the scales of ordinary form which clothe the lovely little wings will occur one here and there of

POLYOMAS ALEXXS. ^ ^^ ^ ^ . ft ^ ^^ jg^^gg

battledore scale of a different shape from the rest. Here than the average; the foot-stalk is very long, and the shape

of the entire scale is that of a battledore. The ribs are rather few and coarse, and they have this peculiarity, that each rib swells at intervals into rounded dilations, each of which has a minute black point in its centre. In some of these battledore scales there is, near the lower part of the expansion, a crescent of minute pigment-grains.

The silvery grey surface of the front wings of a common moth, known as the Buff-tip {Pygcera bucepltala), is composed of scales of unusual magnitude, and of a remarkable form, their shape being that of an expanded fan, and being quite distinguishable by the unassisted eye. The ribs are very fine and numerous, and there are diverging lines of pigment-grains running through the scale.

Those of the Emperor Moth (Saticmia pavonia minor) are likewise triangular in outline, and are remarkable for being deeply notched at the end ; so deeply as to leave projecting points (from two to five) as long as, or even longer than, the undivided portions of the scale.

In some species we find scales the tips of which are furnished with a curious sort of fringe. This slide presents several such in the midst of many of a more ordinary shape and appearance. The scales in question are straight, and parallel-sided, rather narrow, with the basal end rounded, and the terminal ex_ tremity tapered abruptly to a point ; it is on each slope of this point that the fringe is arranged. The surface does not appear to be elevated in ribs, but smooth ; while the whole interior, except a crescent around the foot-stalk, is filled with pigment-grains, imparting a mottled appearance. It is remarkable that all FKIKGKD PIEBIS. SCALB OF the scales of this form have the footstalk turned in under the expanse. The example which G

we are considering is from the white portion of the wing of Pieris Glaucippe, sl fine butterfly from China ; but a similar structure is found in our own Garden Whites and Meadow Browns (Piericlce and Satyridw).

Scales taken from the brilliant changeable blue-o-reen patch in the hind-wing of Papilio Paris, a fine Indian butterfly, have an interesting appearance. They are simply pear-shaped in outline, with few longitudinal ribs set far apart, and numerous strongly marked corrugations running across between them. That these are really elevations of the surface, is well seen in some scales, even with transmitted light, and a high power; for the slopes of the wrinkles that face the light display the lustrous emerald reflection proper to the wing, while the transmitted colour of the whole scale is a rich transparent red.

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