Franklin Russell, Watchers at the pond, New-York, Knopf, 1961.

The worm like larvae of caddis flies were scattered over the bottom of the pond, contained in some of the most effective portable shelters in the pond. Some of the larvae made their shelters from sand and cemented the grains together till they were almost complextely encased in long tubes open at both ends. When sand was not available the larvae used small sticks or cut up sunken leaves and cemented them together. These shelters gave protection against predators but not necessarily against other caddis fly larvae. One caddis worm having lost his shelter when its cemented leaf fragments broke up, swam to another shelter and bit the occupant in the tail. The bitten worm shot out of the tube, and the usurper slid into if to safety.