Is the solution of the puzzle

A. Verrill Hyatt, « Insect Fishermen », Current Literature, vol. 26, New York, 1899, p. 461.

Perchance during some summer’s stroll your steps may lead you by a sparkling, woodland brook. Here pause a moment and placing your face close to the surface of a dark and quiet pool, look closely at the bottom. Among the sand and pebbles you will see a number of small bundles of sticks and little cylinders of tiny stones, moving about as though endowed with life. If you take them out, however, they are apparently dead and entirely devoid of motive power. But break them open and you will find each one to be a little tube lined with soft and shining silk, and containing a whitish caterpillar-like larva. This, then, is the solution of the puzzle—when the grub wishes to move about, he projects the forward portion of his body from the tube and crawls around, dragging his house behind him. But the moment he is disturbed or frightened he draws back into his safe retreat, wherein he remains hidden as long as danger threatens.You will find the little tubes of various kinds shapes ans sizes. Some are cylindrical, made of sticks placed lengthwise, while others are like little log-houses of straw, the pieces being fastened crooswise. These miniature log-cabin are often decorated with tiny snail shells fastened to the walls, and more over, the shells are not always empty. Quite often you may find living snails securely attached and thus compelled to move about at the will of their landlord. Other tubes are built entirely of bits of moss and leaves. The commonest forms are those composed of little pebbles or grains of sand. These are usually very regular and smooth cylinders, in which the grain are all of nearly equal size, but among them you may frequently find some with several larger stones fastened to either side in a very curious manner. By far the prettiest houses of all are shaped like little spiral she lls and are composed entirely of almost microscopical stones.

The little larvae residing in these dainty subaqueous houses are know as Caddice-worms. Not only are the Caddice-worms carpenters and massons, but many species are expert fishermen as well, and between the stones, where the brook runs swiftest, amy be found their silken fish-nets. These nets are funnel-shaped, with the larger opening toward the current, while stretched across the inside are fine threads crossing each other at right angles, the whole forming a fish-trap as ingenious and effective as any constructed by human fishermen. This is the common form of net found in brooks and small streams, but on the edges of falls and cataracts you can find large numbers of nets of quite another sort. These consist of little semi-oval cups fastened to the sides and surface of the rocks and are kept open by the force of the current. These nets catch all manner of small insects and animals on which the Caddice-worms feed. They also catch great quantities of dirt and scum, and it is this rubbish, firmly held in the little silken meshes, that gives to these rocks and stones their coating of dirt in summer.

When the Caddice-worm has attained his full size he draws himself into his little home and builds a silken door across the open end, always leaving a tiny opening through which the water may pass and thus bring him fresh oxygen. Here, safe from harm or molestation, the little fisherman changes to a pupa. In due time the door is broken open and a little insect, whose middle legs are very long and slender, comes forth. Using these long central legs for oars, the newly-hatched creature swims rapidly to the nearest rock or stick, where it crawls out of the water. As soon as it reaches the air, a pair of little pads upon its back expand, as if by magic, into four delicate, hairy, brown wings, with which the insect flies away, showing not the slightest difficulty in using this new means of locomotion.