Charlotte Elizabeth Bowen, Edwin and Mary: or the mother’s cabinet. A book for the Young, Londres, Ward Lock & Co., (1878) 1894, p. 14-15.

Soon after this conversation the two boys fitted up some shelves which their mother sais they might have to keep their curiosities on. William was the first contributor, for he brought from the water’s edge several specimens of the caddis-worm, or case-worm. Nothing can be more curious or more cunningly contrived. The cases were about an inch or an inch and a half long, and as thick as the larger end of a wheat-straw.

One of them was entirely covered with minute shells, some of which were no bigger thana pin’s head, some (the Helix planorbis, or flat-snail shell), were about as big as a split pea: others were spiral and shar-pointed, and others were the shells of young freshwater mussels with the living animals in them, and some were so exceeding small as haedly to be perceived without the help of a magnifying glass.
A second specimen of the case-worm was entirely with bits of stone and grains of sand, so that at first sight it looked like a small long-shaped stone ; but on closer examination it was found to be hollow, like the one that was … /…

A third was covered with very small leaves, and bits of the stalks of water plants, and when freshly taken out of the water, these looked of a bright green colour.
All these William had found on the common by the side of Mill Lane, for the river frequently overflows its banks, and then it leaves a number of shells on the grass. The children had read about case-worms in a book called « Insect Architecture », but they liked much better to see the real insect an dits habitation than to see prints of it, which cannot give any idea of its extreme beauty.
Their mother remarked that the cases of these worms were all perfectly smooth underneath, and she asked if any of them could tell why it was so?…
« I remember » replied Anne, « that Papa told us it was the fly may creep along easily ; he said that if the large stones or larges were below, instead of above, they would either be rubbed off, or they would prevent the animals’ creeping ; but I wonder how they are fastened to the film which covers the fly