Endogenous and exogenous factors affecting host chemical footprint exploitation by a hymenopterous egg parasitoid

Abstract

During the host location process, parasitoids encounter and explore a great variety of volatile and contact semiochemicals from the host-plant complex. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, when wasps land on a plant, they can taste chemical footprints left by walking adult hosts. These cues represent a set of indirect host-related contact kairomones that induce arrestment and motivated searching behavior, as they drive wasps in an area where there is a high probability of finding hosts but are not able to “promise” the presence of the suitable host stage. Patch time allocation is strongly modified by experience gained during foraging on host traces. In fact, when footprint exploitation is not followed by successful oviposition, wasps gradually lose their motivated searching and move back to a more general host searching behaviour. In this work we investigated the effects of exogenous and exogenous factors that can affect the host location behaviour of T. basalis. Trials were recorded and analyzed with the aid of a video tracking and motion analysis system. The potential significance of these results in the host location behavior of T. basalis is discussed.