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Rh designed to take an active share in flight. That function being entirely devolved on the membranous wings, which receive their impulse from the muscles of the metathorax, that segment is proportionably augmented, its dimensions frequently equalling those of the prothorax. These insects undergo a complete metamorphosis. In a few exceptional cases, notwithstanding, the larva bears a close resemblance to the imago, as, for example, in Drilus, the female glow-worm, and almost the whole family of the Staphylinidæ. In such an extensive order, the larvæ are, of course, of very varied aspect; commonly they are soft and pale, the head, and a few of the anterior segments alone being corneous. The absence of the brilliant colours which often distinguish the perfect insect, is to be attributed to their usually frequenting places where they are concealed from the light; some living beneath the ground, others in the stems of trees and herbaceous plants, putrescent fungi, decaying vegetable and animal matter, &c. In such situations long antennæ would be an encumbrance to them, and these appendages accordingly are in all cases short and inconspicuous. Most of them possess six thoracic legs, without any auxiliary organs of motion, but not a few are entirely apodal, the only substitutes for legs being small warts or prominences. Such as are aquatic, effect their motions in the water merely by the action of the legs, aided probably in Gyrinus and Hydrophilus caraboides, by the plumose or fin-like branchiæ placed along the sides of the body. The