the water, and by a curious economy of nature collect round themselves, some, parts of plants, or small sticks; some, gravel; and some, even shell fish. They spin themselves a sort of case of silk from their bodies, and by a gluten, that exudes from this case, cement their materials together. They feed upon aquatic plants, and sometimes upon insects, protruding only their head and legs from the case. When about to undergo transmutation, they quit their cases, rise to the surface, and wait for this process of nature in the air; but some species fix themselves on plants or stones: they burst the skin of the larvæ, and appear perfect animals, male and female, fitted for the office of reproduction. In the early spring, the species which are called green tails, from the colour of the bags of eggs in the female, appear in the warm gleams of sunshine that happen in cloudy days, and they then cover the face of the water, and are greedily seized on by the fish. As the season advances they appear principally in the morning and evening. In the heat of summer the phryganeæ are almost nocturnal flies, and seem to have the habits of moths: at this season, _now_, I should say, the few flies that appear are generally seen in the day-time. The _ephemeræ_, another class of flies peculiarly interesting to the fisherman, differ from the phryganeæ in carrying their wings perpendicularly on their backs, and in having long filaments or hairs in their tails. The March brown, (_see fig._ 8,) the various shades of duns, (_see fig._ 5, 6, and 7,) which I described to you on a former occasion; the green (_see fig._ 9 and 10,) and white May fly, the red spinner, (_see fig._ 11,) are all of the class ephemeræ. These flies are produced from larvæ which inhabit the water, which can both crawl and swim, and which generally live in holes they make in the bottom. They change their coats several times before they become nymphæ. They quit their skin on the surface of the water, but even after they are flies, they have another transformation to undergo before they are perfect animals fitted for generation. They make use of their wings only to fly to some dry bank, or trunk of a tree, where they gradually disencumber themselves of the whole of the outward habiliment they brought from the water, including their wings. They become lighter, more beautiful in colour, and then begin their sports in the sunshine—appearing like what might be imagined of spirits freed from the weight of their terrestrial covering. This last transmutation has been observed and fully described by some celebrated naturalists, in the case of the May flies, and one or two other species, and it probably will be found a general circumstance attached to the class: I have often observed what appeared to me to be the cast-off skins of the small species of ephemeræ on the banks of rivers and floating in the water. The green ephemera, or May fly, lays her eggs