Mayfly, an insect generally placed m the order newoptera, with the dragon Hies, ephemeral, myrmeleon, and termites or white ants, forming the genus phryganea as restricted by Latreille. The jaws are hardly perceptible; the lower wings are broader than the upper, and longitudinally plaited; they have no sting nor piercer, and the antenna? are as long as the body; they undergo complete transformation, larva)' and pupae living in the water and feeding on aquatic insects and plants. The eggs are laid on the leaves of willows and other trees overhanging the water, attached by a viscid matter; the small six-footed larvae, when hatched, fall into the water, and there form for themselves cases of bits of straw, wood, leaves, stones, and shells, cemented together by a glutinous silk; they are hence called case or caddis worms; the larva protrudes its head and shoulders from the case when searching for food; the manner in which these cases are made, ballasted, and balanced affords a striking example of insect architectural ingenuity. (See Rennie's " Insect Architecture.") The pupa is incomplete, and is enclosed in the larva case, at one end of which is a silken grating through which the water for respiration is admitted and ejected; just before quitting the case the grating is cut through by a pair of curved mandibles, and the insect leaves the water by means of the four anterior legs, which areuncon-fined, to assume the perfect state.

The flies as well as the larvae are greedily eaten by fish, and are well known to anglers, who imitate the perfect insects by colored feathers as bait for trout, grayling, etc. Mayflies fly heavily, and generally alight on bushes near the water's edge; most of them are brown with cinereous, greenish, and yellowish markings; they include the willow, alder, green-tail, and dun flies, which cover the surface of the water during the cloudy days of spring, affording plentiful food for fish; as the season advances they appear chiefly in the morning and evening, and during the heat of summer are principally nocturnal. About 300 species are described, one of the largest of which is the P. grandis (Linn.) of Europe, nearly an inch long, with a spread of about 2 in.; the upper wings are brownish gray with cinereous spots, and the antennae as long as the body. Kirby established the order tri-choptera for these insects, which present some peculiarities connecting them with lepidoptera; the larva- resemble the moths in making cases; the perfect insects have the wings hairy but scaleless, without reticulations, and the under ones folded longitudinally; the antennae are like those of moths, and the tibia? are often armed with the two pairs of spurs observable in the latter; but they have not a spiral tongue, and the head has three single eyes as well as the usual compound ones; the abdomen is never furnished with terminal seta?. There are some of the pyralides or delta moths, in the larva state living in leafy eases under water, and feeding on aquatic plants, which seem to make a transition to the trichoptera or this division of the neuroptera. - Another neurop-terous insect, of the suhulicorn family and genus ephemera (Linn.), is also called mayfly; the lower wings are much smaller than the upper, and both are carried perpendicularly; the abdomen is terminated by two or three setae; the antennae are short, and the body is soft, long, and tapering.

These frail creatures appear in the winged state toward evening in summer, often in immense numbers; the E. albipennis, a European species, with white wings, occurs sometimes in such abundance in midsummer as to remind one of a snow storm. The larva? are aquatic, and excavate burrows in the banks of streams under water, in which they are safe from fishes and yet amply supplied with food; after changing their skins several times they become nymphs, with the long caudal appendages and lateral fringes of the larva?, but with rudimentary wing cases in addition; after attaining the winged state, they cast off a complete envelope of skin. Passing a year or two in their imperfect condition, they assume their perfect shape and sport for a few days, perhaps for a few hours only, in the summer day or evening. The fishermen of France call them manna from their furnishing abundant food for fish, covering the surface of the water with their countless swarms in August. (See Rennie's " Insect Transformations.") These are called day flies, and are imitated, as baits for fish.

There are several in America.

Mayfly   Larva and case.

Mayfly - Larva and case.