Into it retreats

Stella Louise Hook, « Under the Ice », New Outlook, vol. 44, Londres, 1891, p. 1278.

There is a time in the history of the caddis when, like a caterpillar, it stops growling, eats no more- for it has caught many a tiny water-animal while moving about – and finally retires into reclusion and forms a kind of chrysalis. Then what a convenience is that ingenious built case ! Into it retreats the caddis, and for further protection spins a strong silken barricade at its open doorway. And here again its wonderful instinct is shown. Enemies must be kept out, but fresh water must be admitted, so the caddis makes its barrier in the form of a grating which effectually answers both purposes. Now it is quite safe and can go to sleep in peace, confident of waking in a new form, with four transparent wings, and power to live and fly in the air like the dragon-fles ; though unlike them, it will lose its preying habits, and flutter harmlessly about, without molesting any of the smaller creatures it may meet upon the wing.
The caddises under the ice water were all youthful ones, apparently, whose cases were still being enlarged from times to time. There might have been some in another part of the brook that preferred a different order of architecture, but they did not seem disposed to show themselves. Some make curved or twisted cases instead of straight ones ; nor are they all formed of sticks: some use leaves, some pebbles, others a promiscuous variety of objects, taking anything that comes within reach for building material, and still others prefer to form their abodes of pure silk.