Arthropod predators use visual, vibratory, and chemical sensory cues for prey location. Sensory information obtained from the cues may result in increased foraging efficiency if the cues are easily detectable and reliable. We investigated the role of a gustatory cue, aphid honeydew (excretion of feeding aphids), in foraging behavior of convergent ladybird beetle (Hippodamia convergens) larvae. We conducted laboratory experiments to examine if the presence, type, and amount of honeydew influences the patch residence time of the predators. We constructed an experimental arena with two patches. Each patch consisted of a petri dish lid and a stick. In one of the patches the lid was clean and in the other one, the lid was covered with honeydew of either pea aphid (Acyrthosiphon pisum) which is a high quality prey and bean aphid (Aphis fabae) which is a low quality prey for the larvae. The goal was to examine if the larvae show differential response to honeydew of the two aphid species that vary in their nutritional quality for the larvae. We videotaped predator searching behavior and used Cox's proportional hazards models to quantify the effect of honeydew presence, type and quantity on the patch leaving behavior of the larvae.
Results/Conclusions
Our preliminary analysis indicated that the presence of honeydew significantly influenced the patch residence time of the ladybird larvae. For both types of honeydew, the higher the quantity of honeydew, the longer the predators stayed in the patch (bean aphid honeydew: p=0.059; pea aphid honeydew: p=0.00012). The quantity of honeydew from low quality bean aphids was smaller compared to the honeydew quantity from high quality pea aphids. To examine if the patch residence time differs between these two honeydew types, we plan to conduct experiments using the same quantity of both honeydew types. We also plan to analyze the videotaped activity pattern (active/inactive time) of the larvae to examine if the duration of an active search is influenced by the type and the quantity of honeydew. A longer search time would increase the probability of encountering plants containing aphid prey, which, in turn, would lead to enhanced prey encounter rates for the ladybird larvae.
