The influence of feeding on predatory tactics in a water bug

International audienceThe tropical belostomatid Diplonychus indicusVenk. & Rao (Heter-optera: Belostomatidae) forages both actively and from ambush, changing frequently from one predatory mode to the other. Analyses presented here of the influence of feeding and of developmental stage on several locomotory and predatory parameters show that the fact that a bug was eating did not prevent it from reacting to and from seizing prey items, but it did influence the mode of predatory attempts. Feeding bugs were less active and they foraged actively less frequently, but feeding did not affect the frequency of predatory attempts from ambush. No important variations during development were found and first stadium larvae behaved similarly to adults. Capture success rates were higher at all developmental stages during a meal than when a bug was not eating and rejection rates were lower during a meal. These results suggest that, when eating, Diplonychus indicus bugs aim more successfully at prey items they are more likely to capture and to eat

Selective predation by Lestes (Odoiiata, Lestidae) on littoral microcrustacea

Two experimental approaches were used to examine the predation risk of six littoral cladoceran and ostracod species to two size classes of the damselfly Lestes sp. Behavioural observations were conducted in a 2–1 arena and predation rate experiments in 1–1 jars in the laboratory.  Behavioural observations revealed that attack and capture efficiencies by Lestes were higher on smaller cladocerans (Polyphemus and Ceriodaphnia) than on other taxa. Small Lestes had little success ingesting the small ostracod Cypridopsis, whereas larger Lestes captured and ate it easily.  Predation‐rate experiments showed that Lestes has a clear preference for smaller cladocerans over both a large cladoceran Simocephatus and all three ostracods (Cypricercus, Cyclocypris, and Cypridopsis). Most Lestes were unable to consume the larger Cypricercus.  Attack rates and predation rates were highly variable among individual predators.  These data indicate that damselfly larvae are size selective and consume all but very large cladocerans more readily than ostracods. Copyright © 1993, Wiley Blackwell. All rights reserve