Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior.

许多类寄生蜂都使用植物挥发物定位其草食宿主。当这些草挥发物在植物中被草食动物诱导释放时，它们是宿主存在的可靠指示。高寄生虫也可能利用来自较低营养水平的信息来定位其寄生虫宿主，但对于植物-宿主复合物挥发物在超寄生虫觅食行为中的作用了解甚少。在这里，我们通过一系列实验研究了蚜虫（Megaspilidae）对植物和宿主挥发物的反应。这种超寄生物使用蚜虫木乃伊作为宿主，并阻碍温室园艺中寄生虫对蚜虫的生物控制。我们发现蚜虫充满木乃伊的甜椒植物中的雌性强烈吸引着雌性，但只有在Y型管嗅觉计中提供了清洁空气作为替代气味源的情况下，雌性才被吸引。当出现蚜虫侵染或健康辣椒植物的挥发物作为替代品时，超寄生虫雌性对木乃伊侵染植物没有偏爱。蚜虫的这些嗅觉反应大多独立于先前的经验。寄主本身的挥发物对蚜虫也极具吸引力，但同样，超寄生性雌性仅在没有植物挥发物的情况下才具有偏爱性。我们的发现表明，植物挥发物可能会混淆，而不是指导蚜虫的觅食行为。木乃伊超寄生物，例如蚜虫可以使用各种各样的木乃伊，因此在较低的营养水平下却是极端通才，这可以解释（诱导的）植物挥发物在其宿主搜索行为中的有限作用。