The importance of vision-reliant defensive traits (e.g. warning colours) in mimicry studies is well established, but their effectiveness is limited by visibility. In low light conditions, for instance, acoustic or tactile channels may be more effective. The juvenile and adult stages of the nocturnal hunting Palpimanus spiders audibly stridulate when harassed. Given this we hypothesized that the sound produced by Palpimanus has a defensive role against interspecific predators. Palpimanus though are poorly defended especially against something as large as a gecko. Hence we hypothesized that the stridulation is effective because the spider mimics co-occurring mutillid wasps. We staged predator feeding experiments in which mutillid wasps, sham-operated Palpimanus, silenced Palpimanus and a nonstridulating spider were offered to Eusparassus spiders and geckoes. Stridulating spiders had significantly greater survival against both predators than the nonstridulating treatments and comparable survival to the mutillid wasps. This result represents the first confirmed case of a spider using stridulation against an interspecific predator. Stridulation deterred Eusparasus spiders, while in geckoes stridulation acted postcapture as they dropped the prey instead of attempting to swallow them. For mutillid wasps this dropping response was typically more rapid than with Palpimanus but attempts to swallow silenced individuals were more frequent than sham-operated individuals, which were more likely to be dropped before any attempt to swallow. Analyses of stridulation characteristics of Palpimanus showed they were similar to acoustic signals of four of the co-occurring mutillid wasps and far more so than distress signals of control insects. Our study overall supports the notion that Palpimanus spiders are Batesian mimics of sympatrically occurring mutillids through the use of an aposematic acoustic signal and not just an example of a startle response.

中文翻译：

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蜘蛛模仿多头黄蜂的声音信号以避免捕食：惊吓信号还是贝氏拟态？

模仿研究中依赖视觉的防御特征（例如警告颜色）的重要性已得到公认，但其有效性受到能见度的限制。例如，在弱光条件下，声学或触觉通道可能更有效。夜间狩猎的触须蛛的幼年和成年阶段在受到骚扰时会发出刺耳的声音。鉴于此，我们假设 Palpimanus 产生的声音对种间捕食者具有防御作用。然而，Palpimanus 的防御能力很差，尤其是对于像壁虎这样大的东西。因此，我们假设鸣叫是有效的，因为蜘蛛模仿了共同发生的多头蜂。我们进行了捕食者喂食实验，其中包括多只黄蜂、假操作的棕榈属、向 Eusparassus 蜘蛛和壁虎提供了沉默的 Palpimanus 和一只不鸣叫的蜘蛛。与非条纹处理相比，条纹蜘蛛对两种捕食者的存活率明显更高，并且与多头黄蜂的存活率相当。这一结果代表了第一个确认的蜘蛛使用针对种间捕食者的叫声的案例。叫声阻止了 Eusparasus 蜘蛛，而在壁虎中，叫声在捕获后起作用，因为它们掉落猎物而不是试图吞下它们。对于mutillid黄蜂，这种丢弃反应通常比Palpimanus更快，但尝试吞咽沉默的个体比假手术的个体更频繁，后者更有可能在任何吞咽尝试之前被丢弃。Palpimanus 的鸣叫特征分析表明，它们与四只同时发生的多头黄蜂的声音信号相似，远比对照昆虫的遇险信号更相似。我们的研究总体上支持这样的观点，即通过使用 aposematic 声学信号而不仅仅是惊吓反应的一个例子，Palpimanus 蜘蛛是同域发生的 mutilids 的贝茨模拟。