The wings of many insects are interesting on account of the organs with which they are clothed. A familiar example is furnished by the common gnat. There is the same general structure as before--two clear elastic membranes stretched over slender horny tubular nervures, and studded on both surfaces with short spine-like hairs, which in this case, however, are excessively numerous and minute. But along the nervures, and along other lines which run (generally) parallel with the front margin, and also along the whole margin, there are set long leaf-like scales of very curious appearance and structure. There are, however, other insects which display these or similar appendages in far greater profusion, and in much variety of form and appearance. In the fissures of cliffs that border the seashore 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 Machilis. 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 colors--red, brown, orange, and yellow, foiled by dull lead-gray in places. If you touch one of these nimble leapers, though ever so slightly, you will see the result on your finger-ends, for they will be found covered with a thin stratum of the finest dust, which displays the colored metallic reflection seen on the insect. By touching one with a plate of glass, instead of your finger, you will get the same dust to adhere to this transparent medium, by applying which to the microscope you may at once discern the marvelous 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. The beautiful and extensive order called Lepidoptera or scale-winged, _par excellence_, including the gay tribes of butterflies and moths, presents us with many exceedingly interesting varieties in these singular coverings.