Ecological segregation of two species of Hydropsyche (Trichoptera: Hydropsychidae) in a European second-order stream (Essonne, France)

Life-history patterns and food habits are described for two sympatric species of Hydropsyche (H. pellucidula and H. contubernalis) sampled for 15 months in a second-order stream, the Essonne (France). Both species showed univoltine lifecycles with remarkable differences in winter. H. contubernalis overwintered mainly in the 4th or 5th larval instar; whereas, the more abundant H. pellucidula overwintered in the 2nd or 3rd larval instar. The main larval growth periods of the two species were also different, and this could be due to ecological segregation, which allows both species to share a similar ecological niche. The two species shared the same food habits throughout all larval instars; however, they both changed their food habits as they passed from one instar to another, and earlier instars were more predatory than the older ones.