Salta al contenuto principale
Passa alla visualizzazione normale.


Endogenous and exogenous factors affecting the host chemical footprint’s exploitation of an egg parasitoid


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 four factors, age (3days-old vs 20days-old), conspecific crowding (isolated or not for 20 days), temperature (4°C vs 25°C) and feeding status (feeding or not for 2 days), on the patch-leaving behaviour of T. basalis. Bioassays were conducted on an open arena made by a filter paper sheet; in the middle, a circular area (4·cm diameter) was defined and exposed for 30·min to a single adult of N. viridula, while the surrounding area was left untreated. 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.