The secret life

Lorus Johnson Milne et Margery Joan Greene, The secret life of animals : pioneering discoveries in animal behaviour, New York , E.P. Dutton, 1975, p. 74.

..Each larva has a slender, caterpillarlike body with two strong hooked legs at its rear end ans six legs near its head, which support it while it walks over algae-coated stones and through water mosses. The larva must find an unoccupied place where the current flows swiftly. Only there can it secure enough food to survie.
When it has chose nits home the caddis worm grips the rock with its two hind claws and lets its body stretch downstream in the water’s flow. Guidey by the six front legs, the bofy swings like a pendulum while the caddis worm makes its net. The insect deftly fastens droplets of saliva linked by slender threads to the rock. These threads become as strong as silk. The first row consists of a curved series of loops attached to the rock and bowed downstream in the middle . Then the caddis worm backs up slightly and fixes another saliva drop to the center of each loop to start its second line of netting. Each row goes slightly farther at the ends than the preceding row so that it can be securely attached to the rock. The net, held taut by the force of the current, does not tear or pull loose, for it is flexible and billows. When the net is finished the caddis worm goes to the end of it and waits. Soon the net will catch a water flea or some small