Effects of two different caddisfly case structures on predation by a dragonfly larva

Abstract

Dragonfly (Odonata) larvae Aeshna juncea L. preyed on two species of cased caddis larva (Trichoptera); Limnephilus pantodapus McLach. with long cylindrical cases and Limnephilus rhombicus L. with “hedgehog”; cases. Direct observations revealed that A. juncea larvae had a significantly shorter reaction time and a significantly longer handling time when preying on L. pantodapus larvae. Number of attacks, captures and ingestions by A. juncea were not significantly different between the two caddis larva. Capture success and ingestion efficiency did not differ significantly. Captures of L. pantodapus larvae were made through the case wall, while L. rhombicus larvae were captured from the front end of the case. In functional response experiments, A. juncea showed a higher attack rate and a longer handling time with L. pantodapus. In a mixed prey situation, a fixed preference for L. pantodapus larvae was apparent, and consequently no indication of switching was found. Observational experiments corroborated data from the functional response experiments.