Predator–prey interactions in a stream: a combined field and laboratory study of Paragnetina media (Plecoptera) and Hydropsyche sparna (Trichoptera)

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Abstract
Substrate size selection, upper and lower substrate surface colonization, and net spinning were examined for the caddisfly Hydropsyche sparna in the presence and absence of the predaceous stonefly Paragnetina media. In the laboratory, I found that when stoneflies were present, caddisflies selected larger substrate and spun fewer nets. Upper and lower surface colonization of substrate did not change as a function of P. media presence. Laboratory findings were consistent with observations made of H. sparna and P. media in the Credit River, Ontario, during midsummer 1983. Based on Hess sample collections, I observed a significant negative correlation between stonefly and caddisfly densities.