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

摘要

Some aspects of the life history of a population of Brachyptera risi were investi-gated in a North Apennine stream and compared with previously studied Euro-pean populations. In our study area, this species showed a univoltine fast seasonallife cycle. Nymphs were present from January to the beginning of May, probablyspending the rest of the year mainly in egg diapause. Fine particulate organic mat-ter was the principal component of the diet, while diatoms and other algae werealso found in the guts. This finding suggests the existence of greater trophic plas-ticity of the species. Individuals of this population act as gatherer-collectors butnot as scrapers as usually pointed out for other European populations. We also de-tected considerable amounts of animal matter in the gut contents. The density ofB. risi nymphs in the study area was very variable during the study period, rang-ing from 0 to 2,348 ind/m2.