Density and Dispersion in Laboratory Populations of Caddisfly Larvae (Cheumatopsyche, Hydropsychidae)

In nature and the laboratory, caddisfly larvae of the genus Cheumatopsyche display aggressive behavior and spacing. It was proposed that their dispersal and subsequent patterns of dispersion would be directly related to density. In experiments at varying densities, in bowls with and without a central refuge of pebbles suitable for case construction, larvae dispersed uniformly in the absence of refuge. When numbers were high, aggressive encounters enforced spacing. In the presence of refuge, they aggregated in the clump of pebbles at all densities. When the refuge was filled to capacity, the excess larvae were forced into the periphery.