Age-related shift in the diet of perla marginata in a woodland Apenninic creek of NW Italy (Plecoptera: Perlidae)

Feeding habits of Perla marginata nymphs have been investigated in the Rio dei Tre Alberghi, an Apennine creek (NW Italy). In this study, gut contents of 62 nymphs of this large sized stonefly were analysed, with the aim to investigate feeding preferences, and to assess the existence of age-related shifts in the trophic spectrum. Evident trophic preferences were detected in the diet: few taxa constituted the greater part of the prey ingested, independently from their availability in the substratum. Also detected was a shift from a detritivorous to a carnivorous diet during the larval growth. This finding is discussed on the basis of ecological and ethological considerations.