Small marginal eyespots on lepidopteran wings are conspicuous elements that attract a predator's attention to deflect attacks away from the body, but the role of ultraviolet (UV) reflectivity at the center of these patterns and variation in eyespot number in altering the function of eyespots remains unclear. Here, we performed a field-based predation experiment with artificial prey items based on the appearance of squinting bush brown butterflies Bicyclus anynana (Butler, 1879). We tested how two visual properties of the wing pattern affect predation risk: i) the number of eyespots on the ventral forewing surface-two or four; and ii) the UV reflectivity of eyespot centers-normal (where the UV reflectivity of the centers contrasts strongly with that of the darker surrounding ring) or blocked (where this contrast is reduced). In total, 807 prey items were deployed at two sites. We found a significant interaction between the number of ventral forewing eyespots and UV reflectivity in the eyespot centers: in items with fewer eyespots, blocking UV resulted in increased predation risk whereas in items with more eyespots, blocking UV resulted in decreased predation risk. If higher predation of paper models can be equated with higher levels of wing margin/eyespot conspicuity, these results demonstrate that UV reflectivity is an important factor in making eyespots more conspicuous to predators and suggest that the fitness of particular butterfly eyespot number variants may depend on the presence or absence of UV in their centers and on the ability of local predator guilds to detect UV.

中文翻译：

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眼斑数量和紫外线反射率对 Bicyclus anynana（鳞翅目：蛱蝶科）捕食风险的相互作用。


鳞翅目翅膀上的小边缘眼点是吸引捕食者注意力以转移攻击远离身体的显眼元素，但这些图案中心的紫外线 (UV) 反射率的作用以及眼点数量的变化在改变眼点功能中的作用仍不清楚。在这里，我们根据斜视灌木棕色蝴蝶 Bicyclus anynana 的外观，使用人工猎物进行了实地捕食实验（Butler，1879）。我们测试了翅膀图案的两种视觉特性如何影响捕食风险：i）前翅腹侧表面上的眼点数量 - 两个或四个； ii) 眼点中心的紫外线反射率 - 正常（中心的紫外线反射率与较暗的周围环的紫外线反射率形成强烈对比）或阻塞（这种对比度降低）。两个地点总共部署了 807 个猎物。我们发现腹侧前翅眼点的数量与眼点中心的紫外线反射率之间存在显着的相互作用：在眼点较少的物品中，阻挡紫外线会导致捕食风险增加，而在眼点较多的物品中，阻挡紫外线会导致捕食风险降低。如果纸模型的较高捕食性可以等同于较高水平的翼缘/眼点显着性，那么这些结果表明，紫外线反射率是使眼点对捕食者更加显眼的重要因素，并表明特定蝴蝶眼点数量变体的适应性可能取决于它们的中心是否存在紫外线，以及当地捕食者协会检测紫外线的能力。