Abstract

Orb-weaving spiders often use their legs to briefly jerk the radii of the web, generating intense vibrations throughout the web. Several functions have been proposed for this behaviour, but there is a lack of empirical evidence. In this study, we conducted a series of experiments on Cyclosa argenteoalba to examine the function and adaptive significance of spider jerks in the context of interactions with prey. First, we used within-individual, inter-individual, and interspecific comparisons (in three co-occurring Cyclosa sp.) to test whether the relation between prey and spider size predict the frequency of jerks that the spider performs. Second, we examined whether jerks prevent prey from escaping the web, whether jerks entangled more spiral threads around the prey, and how prey size affected this result. We found that spiders jerked more as the prey size increased and as spider size decreased. Jerking behaviour reduced the probability of prey escaping from the web and increased the number of spiral threads contacting the prey. The jerk efficiency (the number of additional spiral threads contacted per jerk) was lower in larger prey, which potentially explains why spiders jerk more towards larger prey. Collectively, our results highlight size dependency in the performance of jerks and their role in prey capture.

Significance statements

Many orb-weaving spiders show a behaviour that pulls the radii of the web intensively using their legs towards their prey, called jerks. Though this behaviour is common and has been recognised for many decades, the function and their adaptive significance have been surprisingly understudied. Using a series of experiments, we demonstrate that jerks help spiders prevent prey escape and subdue prey by entangling additional spiral (sticky) threads around the prey. We further show that the performance of jerks is size-dependent: spiders jerk more (1) as their size decreases and (2) as prey size increases. Further in-depth analysis suggests that the observed size-dependent jerks seem to be related to spiders’ cautiousness and/or reduced jerk efficiency towards larger prey.

中文翻译：

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蜘蛛行为增加陷阱效率

摘要

圆球编织蜘蛛经常用它们的腿来短暂地拉动蛛网的半径，在整个蛛网上产生强烈的振动。已经针对这种行为提出了几种功能，但缺乏经验证据。在这项研究中，我们对Cyclosa argenteoalba进行了一系列实验，以检查蜘蛛抽搐在与猎物相互作用的情况下的功能和适应性意义。首先，我们使用了个体内、个体间和种间比较（在三个同时发生的Cyclosasp.) 来测试猎物和蜘蛛大小之间的关系是否可以预测蜘蛛进行抽搐的频率。其次，我们检查了混蛋是否会阻止猎物逃离网络，混蛋是否在猎物周围缠绕了更多的螺旋线，以及猎物大小如何影响这一结果。我们发现，随着猎物尺寸的增加和蜘蛛尺寸的减小，蜘蛛会更加猛烈地抽搐。抽搐行为降低了猎物从网中逃脱的可能性，并增加了与猎物接触的螺旋线的数量。较大的猎物的挺举效率（每个挺举接触的额外螺旋线的数量）较低，这可能解释了为什么蜘蛛更倾向于更大的猎物。总的来说，我们的结果突出了混蛋表现的大小依赖性及其在猎物捕获中的作用。

意义陈述

许多编织圆球的蜘蛛表现出一种行为，即用它们的腿将蛛网的半径集中地拉向猎物，称为抽搐。尽管这种行为很常见并且已经被认可了几十年，但其功能及其适应性意义却令人惊讶地被低估了。通过一系列实验，我们证明了通过在猎物周围缠绕额外的螺旋（粘性）线来帮助蜘蛛防止猎物逃跑和制服猎物。我们进一步表明，猛拉的性能取决于尺寸：蜘蛛在 (1) 尺寸减小时和 (2) 随着猎物尺寸增加时更猛地。进一步深入的分析表明，观察到的与尺寸相关的抽搐似乎与蜘蛛的谨慎和/或对较大猎物的抽搐效率降低有关。