A curious economy

Humphrey Davy, Salmonia: or days of fly fishing, Londres, John Murray, 1832, p.211.

The phryganeae (see figs. 1, 2, 3, and 4), have four wings, which, wheb closed, lie flat ontheir backs, the two upper ones being folded over the lower ones: the flies called by anglers the willow fly, the alder fly, (see fig. 4,) and the dun cut, are of this kind. The phryganeae lay their  eggs on the leaves of willows, or other trees, that overhang the water; they are fastened by a sort of gluten to the surface of the leaf: when hatched, they produce small hexapole larvae, which fall into 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 ase, cement their materials together.