EPHEMERA, day fly, in natural hts tory, a genus of insects of the order Neu roptera. Mouth without mandibles ; feelers four, very short, filiform ; amen nit short, liliform ; above the eyes are two or three large stemmata ; wings erect, the lower ones much shorter ; tail terminating in long bristles or hairs. These short-lived animals, of which there are about twenty species, in two divi sions, according as they have two or three hairs in the tail, are found every where about waters in the summer, and in their perfect state seldom live more than a day or two, some of them not an hour. during which time they perform all the functions of life, and answer all the ends of nature. The larva lives under water, and is eagerly sought after by trout and other fish : it is six-footed, ac tive, and furnished with a tail and six la teral fins or gills ; the pupa resembles the larva, except in having rudiments of future wings. The larva is altogether
aquatic, the complete insect aerial. In the former state it lives two or three years; but as a perfect animal it survives but a very few hours, perishing in the course of the same evening that gives it birth. The most common species in Europe is the E. vulgata, or common Mayfly, so plentiful in the early part of summer about the brinks of rivulets and stagnant waters. It is of a greenish colour, with transparent wings elegantly mottled with brown, and is furnished with three very long black bristles. It flutters in the evening about the surface of the water ; but during the day is generally seen in a quiescent posture, with the wings closed, and applied to each other in an upright position.