Oliver P. Jenkins & Vernon L. Kellogg, « Some water insects », San Francisco, The Western Journal of Education, vol. 4, juin, 1899, p.10.
Firmly attached to stones, especially large ones in swift parts of the stream, may be found small cases (Fig. 36 b) or houses composed of many small pebbles fastened together woth silk. In more quiet place in the stream may be found either attached to stones or resting on the bottom, or sometimes floating in the water, elongate cases (Fig. 37), an inch to two inches long, made of bits of wood fastened together with silk or bits of pine needles or even grass stems tied cleverly together by silken threads. Or tiny cornucopias (fig. 36 a) composed of sand grains, may be found. All these are the cases of the caddice-worms or case-worms, and the caddice-worm itself may be found snuggly concealed in its case. Find and collect as many different kinds of caddice-worms case as you can; find cases with the head and fore part of the body of the worm projecting ; Find cases moving, i. e., dragged by the slowly walking caddis-worm. Examine a caddis-worm carefully; note its long, soft, grub-like body; note that the head and the front part of the body from which arise the legs, namely, that part of the body which projects from the case, has a strong, hard outer wall. What is the case for? To protect the soft, defenseless caddis-worm from the many predaceous animals which live in the brook. Why is the head and front part od the body so much harder than the rest of the body? Can you easily pull the caddis-worm out of its case? How does it hold itself so firmly in its case? By the pair of strong hooks (legs) which are located on the posterior tip of the body. Note that the front pair of legs (how many pairs are there?) are longer than one would expect to find on such a worm-like insect ; what is the reason for this condition of the legs? How does the caddis-worm breathe?
Not all of the caddis-worms live in cases, and some which make cases do not remain in them all of the time, so that you may sometimes find cadis-worms crawling about on the stones. Some of these home-leaving caddis-worms make tiny nets of silk stretched between two near-by stones. These nets are « usually funnel-shaped …….