or Libellula, in the history of insects, a genus of four-winged flies, called in English dragon-flies or adder-flies; the characters of which are these: The mouth is furnished with jaws; the feelers are shorter than the breast; and the tail of the male terminates in a kind of hooked forceps. There are 21 species, chiefly distinguished by their colour. They have all two very large and reticulated eyes, covering the whole surface of the head. They fly very swiftly; and prey upon the wing, clearing the air of innumerable little flies. They are found in August and September in our fields and gardens, especially near places where there are waters, as they have their origin from worms living in that element. The great ones usually live all their time about waters; but the smaller are common among hedges, and the smallest of all frequent gardens. The smaller kind often settle upon bushes, or upon the ground; but the large ones are almost always upon the wing, so that it is very difficult to take them. Their eyes are beautiful objects for the microscope.

The manner of this insect's coupling with the female is a thing that has attracted the observation and admiration of multitudes, as they are frequently seen, in the hotter months, in that state, flying together about the edges of waters.—Mr Homberg of the Academy of Paris has taken a great deal of pains to inform the world of the whole secret of this strange coitus, and of several other remarkable particulars regarding the creature. The species in which he observed it, is the common libella with a blue body, and large black spots on the wings; and is one of the middle size between the largest and least of these creatures, and is very frequent in moist places in June, July, and August. When the male of this species finds the female sitting upon a leaf or stick, he seizes her as she flies, taking fast hold of her, with the hooks at the anus, by the neck, or that part which joins the head to the breast, and immediately flies away with her, holding her fixed by the neck to the end of his tail. It would not be unnatural, on this occasion, to imagine that they were one species of animal running away. away with another to devour it; but this thought must be of short duration, since the female will be soon observed to make no attempts to get away; but, on the contrary, to contrive, as well as she can, to be the better carried, and that with less trouble to the male. He does not however carry his female far before he settles himself upon some plant, and raises his tail so that the female may be brought to sit easily under him upon the same plant. As soon as the female is thus seated, she turns up her tail, and brings it between the legs of the male; then places it to a certain part of the breast of the male, in which are the organs of generation in that sex. All this while the male keeps his hold of her neck with his forelegs or hooks. They usually remain in this posture about three minutes; and, after that, the male gently raising up his breast, they become separated, and leaving the hold he had on her neck at the same time, he flies away as he pleases. The female usually remains on the place for half a quarter of an hour, and then flies away also.—Mr Homberg having observed the coupling of these animals thus far, was determined to examine the organs used in it, by dissection. His anatomical observations may be seen in Mem. Acad. Paris. 1699.