The poor animal

Henry Downes Miles, The Book Field sports containing a complete system of the Veterinary Art, Londres, Henry Doxnes, 1862.

The grub, which are know by the name of caddis worms, case-worms, ruff-coats, cad or cod bait, are the young of flies, which are usually of considerable size, with four large dull-coloured wings, lying in a aluggish manner along the back. The various species of these are know to anglers by the name of stones flies, dun-cut, grannam or green-tail, alder fly, willow fly, spring fly, and caddew fly.
One of the grubs in question forms a pretty case of withered leaves glued together lengthwise, but leaving an opening sufficiently large for the inhabitant to put out its head and shoulders when it wishes to look about for food. Another employed pieces of reed cut into convenient lengths, or of grass, straw, wood, &c., carefully joining and cementing each piece to its fellow, as the work proceds ; and he frequently finishes the whole by adding a broad piece, longer than the rest, to shade his doorway overhead so that he may not be seen by any fish above. Another of these aquatic architects makes choice of the tiny shells of young fresh-water mussels, and snails, to form a movable grotto ; and as these little shells are for the most part inhabited, he keeps the poor animal close prisoners, and drags them along with him. These grotto-building grubs are by no mean uncommon in ponds; and in chalk districts, such as the country about Woolwich and Gravesend, they are very abundant. One of the most surprising instances of their skill occurs in the structures of which small stones are the principal materials.
In some instances, when the materials are found to possess too great specific gravity, a bit of light wood, or a hollow straw, is added to buoy up the case, being soft like a mealworm or garden caterpillar , while the head and shoulders, which are for the most part projected beyond the door-way in search of food, are firm, hard, and consequently less liable to injury then the protected portion, should it chance to be exposed.