There is increasing evidence that microorganisms, particularly fungi and bacteria, emit volatile compounds that mediate the foraging behaviour of insects and therefore have the potential to affect key ecological relationships. However, to what extent microbial volatiles affect the olfactory response of insects across different trophic levels remains unclear. Adult parasitoids use a variety of chemical stimuli to locate potential hosts, including those emitted by the host’s habitat, the host itself, and microorganisms associated with the host. Given the great capacity of parasitoids to utilize and learn odours to increase foraging success, parasitoids of eggs, larvae, or pupae may respond to the same volatiles the adult stage of their hosts use when locating their resources, but compelling evidence is still scarce. In this study, using Saccharomyces cerevisiae we show that Trichopria drosophilae, a pupal parasitoid of Drosophila species, is attracted to the same yeast volatiles as their hosts in the adult stage, i.e. acetate esters. Parasitoids significantly preferred the odour of S. cerevisiae over the blank medium in a Y-tube olfactometer. Deletion of the yeast ATF1 gene, encoding a key acetate ester synthase, decreased attraction of T. drosophilae, while the addition of synthetic acetate esters to the fermentation medium restored parasitoid attraction. Bioassays with individual compounds revealed that the esters alone were not as attractive as the volatile blend of S. cerevisiae, suggesting that other volatile compounds also contribute to the attraction of T. drosophilae. Altogether, our results indicate that pupal parasitoids respond to the same volatiles as the adult stage of their hosts, which may aid them in locating oviposition sites.

越来越多的证据表明，微生物，尤其是真菌和细菌，会释放出挥发性化合物来调节昆虫的觅食行为，因此有可能影响关键的生态关系。然而，微生物挥发物在多大程度上影响昆虫在不同营养级别的嗅觉反应仍不清楚。成虫使用各种化学刺激来定位潜在宿主，包括宿主栖息地、宿主本身和与宿主相关的微生物释放的那些。鉴于寄生蜂利用和学习气味以提高觅食成功率的巨大能力，卵、幼虫或蛹的寄生蜂可能会对宿主成虫阶段在定位资源时使用的相同挥发物做出反应，但仍然缺乏令人信服的证据。在本研究中，使用Saccharomyces cerevisiae我们表明，果蝇属的一种蛹寄生物果蝇 Trichopria drosophilae被吸引到与其在成虫阶段的宿主相同的酵母挥发物，即醋酸酯。在 Y 型管嗅觉计中，与空白培养基相比，拟寄生物明显更喜欢酿酒酵母的气味。删除编码关键醋酸酯合酶的酵母ATF1基因会降低对果蝇的吸引力，而向发酵培养基中添加合成醋酸酯可恢复对寄生物的吸引力。对单个化合物的生物测定表明，单独的酯类不如酿酒酵母的挥发性混合物那么有吸引力，表明其他挥发性化合物也有助于吸引果蝇。总而言之，我们的结果表明，蛹寄生物对与其宿主成虫阶段相同的挥发物有反应，这可能有助于它们定位产卵地点。