Selective predation on cladocerans by common pond insects

Abstract

A variety of common pond insects was presented with a mixture of different size classes of Daphnia magna or different sizes of Daphia pulex, Moina affinis, and Ceriodaphnia sp. in predation trials. Juvenile Belostoma flumineum and most instars of Notonecta undulata and Anax Junius fed at the highest rates on the largest available cladoceran prey, and late-instar Buenoa corfusa fed at the highest rates on prey between 0.8 and 2.0 mm in length. Predation rates of instar IV Chaoborus americanus larvae were highest on Daphnia < 1 mm in length, and lowest on Daphnia > 2 mm in length. First-instar Chaoborus larvae did not eat cladocerans in these trials. The size-selective feeding patterns exhibited by Notonecta adults and late-instar Anax were similar in the light and dark, although overall feeding rates were depressed in the dark. Buenoa, on the other hand, only exhibited size-selective feeding in the light. The results indicate, however, that all of these insect predators can feed in the dark. Predation rates for late-instar Chaoborus larvae were unaffected by light conditions or the presence of filamentous algae. Chaoborus larvae were readily eaten by late-instar Notonecta and Anax.