EPHEMERA (Gr. lasting for a day), a Linnman genus of neuropterous insects, now forming the family or tribe ephemerides. They are allied to the libellulidos, or dragon flies, but differ from them in many very important respects. They have received their name, to which corresponds the English DAY-FLY, sometimes also applied to them, from the brief duration of their existence in the perfect state, in which, very unlike the dragon-flies, they are believed to take no food, merely propagating their species, and dying. From the season of the year in which they begin to be seen, some of them are also called MAY-FLY; and by this name are well known to anglers, who use them, and artificially imitate them as excellent lures for trout. The eggs of the ephemerae are also a favorite food of fishes; they cohere together in a gelatinous mass. The larvae and pupae are aquatic, and in these states the ephemerae have a much longer life than in their perfect state, extending even to years. The larvae and pupa?, are sufficiently voracious. The abdomen of the larva is furnished on each side with a set of leaflets, which servo instead of gills for respiration, and arc also used in locomotion, although there are 6 ft. attached to the thoracic segments. The pupae differ little from the larvae except iu hav ing rudimentary wings inclosed under scales. Both larvce and pupa have the abdomen terminated by two or three jointed filaments, which the perfect insect also has, some times very long. The body of the perfect insect is soft and slender; the wings resemble
in form those of dragon-flies, but are soft and filmy; in repose, they are elevated ver tically above the body; the second pair of wings are much smaller than the first, and in some species are altogether wanting; the organs of the mouth are so soft and small as not easily to be discerned, and to be apparently unfit for any kind of use. Ephemerae, in their larva and pupa states, live chiefly under stones in water, or in burrows which they make in the banks of streams. When ready for their final change, they creep out of the water to undergo it on some plant or other object by the water-side, generally towards sunset on some fine day of summer or autumn. Alter having attained their winged state, however, they cast off a complete slough or envelope, so perfect, that it exhibits even the limbs, abdominal filaments, and antennae; and these "ghost-like exuvim" are sometimes so abundant in the neighborhood of streams, as to cover in "a pearly layer " the hat and basket of the angler. The multitudes of ephemerae are often very great, filling the air as a cloud; nay, so abundant are they at times, that their bodies have been known to cover the ground in certain districts of France, and have been gathered from particular spots in cart-loads to be used as manure.