Interpreting the diet of Rhyacophila larvae (Trichoptera) from gut analyses: an evaluation of techniques

Publisher Website
Google Scholar
Abstract
Three commonly used gut analysis techniques were compared for reliability in determining the food habits of fifth-instar Rhyacophila fuscula (Walker) larvae. The predaceous Rhyacophila were fed a known number of each of two prey taxa (Ephemeroptera; Ephemerellidae, and Diptera: Chironomidae) in an artificial stream under controlled conditions in the laboratory. Rhyacophila attacked equal numbers of both prey types during the experiment. Two gut analysis techniques, (1) frequency of occurrence of particular prey in the guts, and (2) the relative abundance of each prey in the guts, gave results similar to those expected. The third technique, a frequently used quantitative method which uses relative areas of the diet items, gave a significantly biased interpretation of prey selection by R. fuscula. The indiscriminate application of any of these methods may lead to errors in interpreting the diet of individual predator taxa, and consequently, incorrect conclusions in studies of comparative feeding ecology.