While it is well documented that insects exploit polarized sky light for navigation, their use of reflected polarized light for object detection has been less well studied. Recently, we have shown that the small white butterfly, Pieris rapae, distinguishes between host and non-host plants based on the degree of linear polarization (DoLP) of light reflected from their leaves. To determine how polarized light cues affect host plant foraging by female P. rapae across their entire visual range including the ultraviolet (300-650 nm), we applied photo polarimetry demonstrating large differences in the DoLP of leaf-reflected light among plant species generally and between host and non-host plants specifically. As polarized light cues are directionally dependent, we also tested, and modelled, the effect of approach trajectory on the polarization of plant-reflected light and the resulting attractiveness to P. rapae. Using photo polarimetry measurements of plants under a range of light source and observer positions, we reveal several distinct effects when polarized reflections are examined on a whole-plant basis rather than at the scale of pixels or of entire plant canopies. Most notably from our modeling, certain approach trajectories are optimal for foraging butterflies, or insects generally, to discriminate between plant species on the basis of the DoLP of leaf-reflected light.

中文翻译：

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进场轨迹和太阳位置影响寄主植物对小白蝴蝶的吸引力

尽管有充分的文献证明昆虫利用偏振的天光进行导航，但对反射偏振光用于物体检测的研究却很少。最近，我们已经发现，小的白色蝴蝶Pieris rapae基于叶片反射的光的线性偏振度（DoLP）区分宿主植物和非宿主植物。为了确定偏振光线索如何影响雌性菜青虫在整个可见光范围内（包括紫外线（300-650 nm））对寄主植物的寄主觅食，我们应用了光偏光法，证明了一般植物物种之间叶片反射光的DoLP差异很大，并且特别是在宿主植物和非宿主植物之间。由于偏振信号的方向是相关的，因此我们也进行了测试和建模，进场轨迹对植物反射光偏振的影响以及对菜青虫的吸引力。通过在一定光源和观察者位置范围内对植物进行光偏振测量，我们发现在整个植物而不是像素或整个植物冠层的范围内检查偏振反射时，会发现几种不同的效果。最值得注意的是，根据我们的建模，某些进场轨迹最适合觅食蝴蝶或昆虫，以根据叶片反射光的DoLP区分植物种类。当在整个植物的基础上而不是在像素或整个植物冠层的尺度上检查偏振反射时，我们揭示了几种不同的效果。最值得注意的是，根据我们的建模，某些进场轨迹最适合觅食蝴蝶或昆虫，以根据叶片反射光的DoLP区分植物种类。当在整个植物的基础上而不是在像素或整个植物冠层的尺度上检查偏振反射时，我们揭示了几种不同的效果。最值得注意的是，根据我们的建模，某些进场轨迹最适合觅食蝴蝶或昆虫，以根据叶片反射光的DoLP区分植物种类。