Predator escape behaviour is a critical component of dragonfly life history. Flight initiation distance is the distance at which escape commences, and is well studied in vertebrates, barely studied in invertebrates, and entirely unstudied in dragonflies. Here we test four principles regarding flight initiation distance as derived from studies of vertebrates to examine if they apply to dragonflies in Sri Lanka: (1) flight initiation distance is a species-specific trait; (2) flight initiation distance increases with starting distance (the distance at which the experimenter begins an approach); (3) larger individuals have longer flight initiation distances; and (4) flight initiation distance varies between the sexes in some species. We collected 105 flight initiation distances from 11 species (known sex and size). Flight initiation distances varied between species and positively with starting distance. In one of three data-rich species (n ≥ 10), flight initiation distance was positively associated with body length. Flight initiation distance did not vary with sex in our sample. Escape responses evoked by standardised human approaches represent a fruitful methodology to study dragonfly escape behaviour in the wild.

中文翻译：

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蜻蜓的飞行起始距离是物种特异性的，与起始距离正相关，有时与体长正相关

捕食者逃逸行为是蜻蜓生活史的重要组成部分。飞行起始距离是逃逸开始的距离，在脊椎动物中得到了很好的研究，在无脊椎动物中几乎没有研究过，在蜻蜓中完全没有研究过。在这里，我们测试了源自脊椎动物研究的关于飞行起始距离的四个原则，以检查它们是否适用于斯里兰卡的蜻蜓：（1）飞行起始距离是一个物种特异性特征；(2) 飞行起始距离随着起始距离（实验者开始进场的距离）而增加；(3) 个体较大的个体飞行起始距离较长；(4) 某些物种的两性之间的飞行起始距离不同。我们收集了 11 个物种（已知性别和大小）的 105 个飞行起始距离。飞行起始距离因物种而异，并且与起始距离呈正相关。在三个数据丰富的物种之一（n≥10）中，飞行起始距离与体长呈正相关。在我们的样本中，飞行起始距离不随性别而变化。由标准化的人类方法引起的逃逸反应代表了研究野外蜻蜓逃逸行为的一种富有成效的方法。