Chemical cues play important roles in predator–prey interactions. Semiochemicals can aid predator foraging and alert prey organisms to the presence of predators. Previous work suggests that predator traits differentially influence prey behavior, however, empirical data on how prey organisms respond to chemical cues from predator species with different hunting strategies, and how foraging predators react to cues from potential competitors, is lacking. Furthermore, most research in this area has focused on aquatic and aboveground terrestrial systems, while interactions among belowground, soiling-dwelling organisms have received relatively little attention. Here, we assessed how chemical cues from three species of entomopathogenic nematodes (EPNs), each with a different foraging strategy, influenced herbivore (cucumber beetle) and natural enemy (EPN) foraging behavior. We predicted these cues could serve as chemical indicators of increased predation risk, prey availability, or competition. Our findings revealed that foraging cucumber beetle larvae avoided chemical cues from Heterorhabditis bacteriophora (active-foraging cruiser EPNs), but not Steinernema carpocapsae (ambusher EPNs) or Steinernema riobrave (intermediate-foraging EPNs). In contrast, foraging H. bacteriophora EPNs were attracted to cues produced by the two Steinernema species but not conspecific cues. Notably, the three EPN species produced distinct blends of olfactory cues, with only a few semi-conserved compounds across species. These results indicate that a belowground insect herbivore responds differently to chemical cues from different EPN species, with some EPN species avoiding prey detection. Moreover, the active-hunting EPNs were attracted to heterospecific cues, suggesting these cues indicate a greater probability of available prey, rather than strong interspecific competition.

化学线索在捕食者 - 猎物相互作用中发挥重要作用。化学信息素可以帮助捕食者觅食并提醒猎物生物注意捕食者的存在。以前的工作表明，捕食者的特征对猎物行为有不同的影响，但是，缺乏关于猎物生物如何对具有不同狩猎策略的捕食者物种的化学线索作出反应的经验数据，以及觅食的掠食者如何对来自潜在竞争者的线索作出反应的经验数据。此外，该领域的大多数研究都集中在水生和地上陆地系统上，而地下、土壤栖息生物之间的相互作用受到的关注相对较少。在这里，我们评估了来自三种昆虫病原线虫 (EPN) 的化学线索是如何产生的，每种都有不同的觅食策略，影响食草动物（黄瓜甲虫）和天敌（EPN）的觅食行为。我们预测这些线索可以作为增加捕食风险、猎物可用性或竞争的化学指标。我们的研究结果表明，觅食的黄瓜甲虫幼虫避免了来自Heterorhabditis bacteriophora（主动觅食巡洋舰 EPNs），但不是Steinernema carpocapsae（伏击 EPNs）或Steinernema riobrave（中间觅食 EPNs）。相比之下，觅食的H. bacteriophora EPN 被两个Steinernema产生的线索所吸引种而不是同种的线索。值得注意的是，这三种 EPN 物种产生了不同的嗅觉线索混合物，跨物种只有少数半保守的化合物。这些结果表明，地下昆虫食草动物对来自不同 EPN 物种的化学线索的反应不同，一些 EPN 物种避免了猎物检测。此外，主动狩猎的 EPN 被异种特异性线索所吸引，这表明这些线索表明可用猎物的可能性更大，而不是强烈的种间竞争。