Predators often reduce movement speeds and turn frequency upon encounters with prey (area-restricted search), thereby causing the predator to spend more time in patches with higher densities of prey. Because patches may vary not only in prey density but also in prey quality, we investigated whether prey quality influences the area-restricted search behavior of a generalist predator. To increase the likelihood of detecting a significant effect of prey quality on predator searching behavior, we chose prey species (black bean aphids, Aphis fabae, and pea aphids, Acythrosiphon pisum) that differed substantially in quality as prey for predatory larvae of the convergent ladybird beetle (Hippodamia convergens). To quantify search behavior, we digitized movement paths of ladybird larvae fed either a low quality aphid (A. fabae) or a high quality aphid (A. pisum). We predicted that ladybird larvae fed low quality aphids would not engage in area-restricted search, which would lead to shorter patch residence times compared to ladybird larvae fed high quality aphids.
Results/Conclusions

Contrary to our predictions, the mean movement speed of ladybird larvae (a component of area-restricted search) was the same after consuming high and low quality prey. Most low quality aphids were only partially consumed and their consumption was followed by long bouts of inactivity suggesting that low quality prey may have a toxic effect on predators. The significantly reduced activity level contributed to ladybird larvae spending significantly more time in the patch after eating a low quality aphid than after eating a high quality aphid. We are currently conducting a more detailed analysis of the movement data, but our preliminary conclusion is that prey quality has no effect on the searching behavior of ladybird larvae.