The dragon-flies of that remote epoch were very like those of to-day, whose dancing flights and graceful, swooping movements are such a delight to watch by reed-fringed pools, or river-banks, during the sweltering days of summer. This flight is very different from that of a bird, though it would be hard to say precisely in what it differs. But we have no such difficulty in regard to the broad outlines of the mechanism of such flight. To begin with there are two pairs of wings, and these appear to be fashioned out of some curiously gauze-like material, a sort of mesh-work tissue, often strikingly coloured. And they are obviously driven after a very different fashion from those of the bird. For in the bird they are moved by quivering muscles, attached to a bony, internal skeleton. In the dragon-fly--as with all insects--the hard skeleton, composed of a material known as "chitin," forms the outside of the body and encloses the muscles. Finally, for we may not dwell very long over this aspect of flight, it is clear that the wings cannot have been derived from modified fore-legs, like those of the bat, or the bird. Rather, it would seem, they have developed out of plate-like breathing organs. The restful twilight hours of summer tempt not only bats from their hiding places, but a host of other winged creatures which are rarely to be seen, or heard, during the glare of noon. Among these is the lumbering dor-beetle, who, with lazy drone steers clear of solid objects only with difficulty. Many, indeed, are his failures. He and his kin are no match for bats and owls, who find them juicy morsels! On the next opportunity catch one and examine him. His wings are curiously interesting. There are the usual two pairs: but the fore-wings have been changed to serve as covers for the hind-wings. During flight they are spread outwards, and indirectly, no doubt, assist flight. But the hind-wings are the real propellers. And it will be noticed that when not in use they can be folded up in a perfectly wonderful manner, so as to lie completely underneath the fore-wings, or "elytra," so that when the creature is crawling it appears to be wingless. Now compare these with the transparent wings of the bee, or the gorgeously scale-covered wings of the butterfly. It is well worth while. If this examination be done very carefully, and with the aid of a magnifying glass, it will be found that the fore and hind wings are yoked together in the wing of the bee, by a delicate mechanism of hooks. In the moths, but not in the butterflies, a bristle, or sometimes two or three bristles, serve the same purpose. Further, in the case of the bee it will be found that the fore-wing, when at rest, is folded longitudinally back upon itself. Finally, turn to the flies. Herein it will be seen that there is but a single pair of wings, the hind pair having become reduced to mere stumps, known as "balancers."