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Family Libellulidae

This is one of the largest dragon-fly groups in the United States, and comprises some of the most beautiful species. With many forms the wings are beautifully banded with brown, either in a series of cross bands or with large blotches which sometimes cover the basal half of the wings. The abdomens of some species are covered with a whitish powder-like substance which is not seen when the insects first emerge from the nymph, but which, when they grow old is sometimes so abundant as to make the abdomen appear perfectly white. A characteristic feature of these forms, especially those of the typical genus Libellula is that the abdomen assumes the shape of a prism, with a strong sharp longitudinal ridge above the flat sides and a flat underside. In some forms the wing markings are not dull brown, but become yellowish and in the very handsome and common Libellula pulchella, of Drury, the brown spots alternate with milk-white spots. They are very abundant about stagnant ponds and such pools as harbor water-lilies and rushes. They are favorite food of the king bird.

The females poise themselves close to the surface of the water, remaining almost motionless and striking the water with the tip of the abdomen in the act of laying their eggs.

With the exception of the Agrionidae these are the most numerous dragon-flies in this country.

Needham says that the nymphs are sprawlers upon the bottom, mainly in shallow water, or clamber over fallen plant stems, and are protectively colored.

A single egg-mass of one of these dragon-flies has been observed by Needham to contain 110,000 eggs.

Williamson has shown that one of the species has the habit of resting on the top of a rush, each one being, apparently, proprietor of a certain territory. When another one encroaches, "he is quickly hustled away by the rightful and irate owner."