Experience of host-associated olfactory stimuli during development affects subsequent foraging decisions in many parasitoids, leading to host fidelity. We have recently shown that odours emitted by an alien host-plant complex (HPC) may affect this learning process. However, the consequences of this olfactory experience on parasitoid host foraging decisions is unknown. Here, we investigated if olfactory preferences induced by experience might drive parasitoid HPC choice and oviposition decisions. We presented two HPCs in dual choice experiments to Aphidius ervi females that had been reared on each HPC, either in a simple (one HPC) or complex (two HPCs) olfactory environment. HPC choice, time before landing on a HPC and number of aphid attacks were recorded. Early experience had contrasting effects on each of these parameters. Regardless of their origin, parasitoids did not land preferentially on any HPC, but they more frequently attacked one of the two hosts (Acyrthosiphon pisum) once they had landed on its HPC. Females emerging from the A. pisum/faba bean HPC attacked more aphids, regardless of the host species. Finally, the olfactory complexity of the environment had inconsistent effects on foraging decisions. These observations, contrasting with previous results obtained in olfactometer assays, indicate that olfactory preferences induced in early stages are not sufficient to predict parasitoid oviposition decisions. Moreover, the integration of multiple signals at several scales might generate different foraging patterns at each step of the host selection process.

发育过程中与宿主相关的嗅觉刺激的经验会影响许多寄生虫的后续觅食决策，从而导致宿主保真。我们最近发现，外来宿主植物复合物（HPC）散发出的气味可能会影响此学习过程。但是，这种嗅觉经验对拟寄生物宿主觅食决策的影响尚不清楚。在这里，我们调查了由经验引起的嗅觉偏好是否可能导致寄生性HPC选择和产卵决策。我们在Aphidius ervi的双选实验中展示了两种HPC在简单（一个HPC）或复杂（两个HPC）嗅觉环境中饲养在每个HPC上的雌性。记录HPC选择，降落到HPC之前的时间和蚜虫攻击的次数。早期经验对每个参数都有相反的影响。不论其起源如何，寄生虫都不会优先降落在任何HPC上，但一旦降落在其HPC上，它们就会更频繁地攻击两个宿主之一（蚜虫（Acyrthosiphon pisum））。雌性从A. pisum出现/ faba bean HPC攻击了更多的蚜虫，而与宿主物种无关。最后，环境的嗅觉复杂性对觅食决策产生了不一致的影响。这些观察结果与嗅觉测定中以前的结果相反，表明在早期阶段诱导的嗅觉偏好不足以预测拟寄生物的产卵决策。此外，多个信号在多个尺度上的集成可能在主机选择过程的每个步骤中生成不同的觅食模式。