Insects live in a dangerous world and may fall prey to a wide variety of predators, encompassing multiple taxa. As a result, selection may favour defences that are effective against multiple predator types, or target-specific defences that can reduce predation risk from particular groups of predators. Given the variation in sensory systems and hunting tactics, in particular between vertebrate and invertebrate predators, it is not always clear whether defences, such as chemical defences, that are effective against one group will be so against another. Despite this, the majority of research to date has focused on the role of a single predator species when considering the evolution of defended prey. Here we test the effectiveness of the chemical defences of the wood tiger moth, a species previously shown to have defensive chemicals targeted towards ants, against a common invertebrate predator: spiders. We presented both live moths and artificial prey containing their defensive fluids to female Trichonephila senegalensis and recorded their reactions. We found that neither of the moth’s two defensive fluids were able to repel the spiders, and confirmed that methoxypyrazines, a major component of the defences of both the wood tiger moth and many insect species, are ineffective against web-building spiders. Our results highlight the variability between predator taxa in their susceptibility to chemical defences, which can in part explain the vast variation in these chemicals seen in insects, and the existence of multiple defences in a single species.

中文翻译：

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测试吡嗪防御蜘蛛的有效性

昆虫生活在危险的世界中，可能会成为包括多种生物群在内的各种天敌的猎物。结果，选择可能偏向于针对多种捕食者类型有效的防御措施，或针对特定目标的防御措施，这些防御措施可以降低来自特定种类掠食者的捕食风险。鉴于感觉系统和狩猎策略的变化，特别是在脊椎动物和无脊椎动物掠食者之间的变化，并不总是很清楚，针对一个群体有效的防御（例如化学防御）是否会针对另一个群体。尽管如此，迄今为止，大多数研究都集中在考虑被保护猎物的进化时单个捕食物种的作用上。在这里，我们测试了木虎蛾化学防御的有效性，一种先前显示具有针对蚂蚁的防御性化学物质的物种，可对抗常见的无脊椎动物捕食者：蜘蛛。我们向女性展示了含有防蛀液的活蛾和人工猎物塞内加尔毛癣菌并记录了它们的反应。我们发现，蛾的两种防御液都不能排斥蜘蛛，并证实甲氧基吡嗪类（对木老虎蛾和许多昆虫而言都是防御的主要成分）对构建蜘蛛网无效。我们的研究结果突显了捕食类群对化学防御的敏感性之间的差异，这可以部分解释昆虫中所见这些化学物质的巨大差异，以及单个物种中存在多种防御作用。