The intestinal contents of the nymphs of 9 species of stoneflies belonging
to the families Perlodidae, Perlidae, Taeniopterygidae, Capniidae and Leuctridae
have been studied, analysing the variations in different size categories. Our
study provides the first data on feeding in the genera Hemimelaena and Capnioneura.
On the basis of vegetable matter quantities, we found that in the carnivorous
species this fraction of the diet diminished in the series Hemimelaena-Isoperla-
Perla. The dietary habits of the different species belonging to the families
Taeniopterygidae, Nemouridae, Capniidae and Leuctridae were found to be
similar since all of these behave fundamentally as detritivores-herbivores. In
almost all these latter species, except Nemoura lacustris, we found that over the
two size intervals considered, fine organic matter was consumed mainly by the
younger nymphs and coarse organic matter mainly by the older ones.