Abstract To locate mating partners and essential resources such as food, oviposition sites and shelter, insects rely to a large extent on chemical cues. While most research has focused on cues derived from plants and insects, there is mounting evidence that indicates that micro-organisms emit volatile compounds that may play an important role in insect behaviour. In this study, we assessed how volatile compounds emitted by phylogenetically diverse bacteria affected the olfactory response of the primary parasitoid Aphidius colemani and one of its secondary parasitoids, Dendrocerus aphidum. Olfactory responses were evaluated for volatile blends emitted by bacteria isolated from diverse sources from the parasitoid's habitat, including aphids, aphid mummies and honeydew, and from the parasitoids themselves. Results revealed that A. colemani showed a wide variation in response to bacterial volatiles, ranging from significant attraction over no response to significant repellence. Our results further showed that the olfactory response of A. colemani to bacterial volatile emissions was different from that of D. aphidum. Gas chromatography-mass spectrometry analysis of the volatile blends revealed that bacterial strains repellent to A. colemani produced significantly higher amounts of esters, organic acids, aromatics and cycloalkanes than attractive strains. Strains repellent to D. aphidum produced significantly higher amounts of alcohols and ketones, whereas the strains attractive to D. aphidum produced higher amounts of the monoterpenes limonene, linalool and geraniol. Overall, our results indicate that bacterial volatiles can have an important impact on insect olfactory responses, and should therefore be considered as an additional, so far often overlooked factor in studying multitrophic interactions between plants and insects. A free Plain Language Summary can be found within the Supporting Information of this article.

中文翻译：

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与寄生蜂栖息地相关的细菌挥发物在蚜虫寄生蜂及其超寄生蜂中引起不同的嗅觉反应

摘要 为了定位交配对象和食物、产卵地点和庇护所等基本资源，昆虫在很大程度上依赖于化学线索。虽然大多数研究都集中在来自植物和昆虫的线索上，但越来越多的证据表明，微生物释放出的挥发性化合物可能在昆虫行为中发挥重要作用。在这项研究中，我们评估了由系统发育不同的细菌释放的挥发性化合物如何影响初级寄生蜂蚜虫及其次级寄生蜂之一，Dendrocerus aphidum 的嗅觉反应。对从寄生蜂栖息地的不同来源（包括蚜虫、蚜虫木乃伊和蜜露）以及寄生蜂本身分离的细菌释放的挥发性混合物进行了嗅觉反应评估。结果显示，A. colemani 对细菌挥发物的反应表现出很大的变化，从显着的吸引到无反应到显着的排斥。我们的结果进一步表明，A. colemani 对细菌挥发性排放物的嗅觉反应与 D. aphidum 不同。挥发性混合物的气相色谱-质谱分析表明，与有吸引力的菌株相比，对 A. colemani 具有排斥性的细菌菌株产生的酯、有机酸、芳烃和环烷烃的量明显更高。对蚜虫具有排斥性的菌株产生显着更高量的醇和酮，而对蚜虫具有吸引力的菌株产生更多的单萜类柠檬烯、芳樟醇和香叶醇。全面的，我们的结果表明，细菌挥发物可以对昆虫的嗅觉反应产生重要影响，因此应该被视为一个额外的、迄今为止在研究植物和昆虫之间的多营养相互作用时经常被忽视的因素。可以在本文的支持信息中找到免费的普通语言摘要。