Nymphal biology of brachyptera risi (Morton, 1896) (Plecoptera: Taeniopterygidae) in a North apennine stream (Italy)

Some aspects of the life history of a population of Brachyptera risi were investigated in a North Apennine stream and compared with previously studied European populations. In our study area, this species showed a univoltine fast seasonal life cycle. Nymphs were present from January to the beginning of May, probably spending the rest of the year mainly in egg diapause. Fine particulate organic matter was the principal component of the diet, while diatoms and other algae were also found in the guts. This finding suggests the existence of greater trophic plasticity of the species. Individuals of this population act as gatherer-collectors but not as scrapers as usually pointed out for other European populations. We also detected considerable amounts of animal matter in the gut contents. The density of B. risi nymphs in the study area was very variable during the study period, ranging from 0 to 2, 348 ind/m².