Almost all species of the orchid genus Ophrys are pollinated by sexual deception. The orchids mimic the sex pheromone of receptive female insects, mainly hymenopterans, in order to attract males seeking to copulate. Most Ophrys species have achromatic flowers, but some exhibit a coloured perianth and a bright, conspicuous labellum pattern. We recently showed that the pink perianth of Ophrys heldreichii flowers increases detectability by its pollinator, males of the long-horned bee Eucera berlandi. Here we tested the hypothesis that the bright, complex labellum pattern mimics the female of the pollinator to increase attractiveness toward males. In a dual-choice test we offered E. berlandi males an O. heldreichii flower and a flower from O. dictynnae, which also exhibits a pinkish perianth but no conspicuous labellum pattern. Both flowers were housed in UV-transmitting acrylic glass boxes to exclude olfactory signals. Males significantly preferred O. heldreichii to O. dictynnae flowers. In a second experiment, we replaced the perianth of both flowers with identical artificial perianths made from pink card, so that only the labellum differed between the two flower stimuli. Males then chose between both stimuli at random, suggesting that the presence of a labellum pattern does not affect their choice. Spectral measurements revealed higher colour contrast with the background of the perianth of O. heldreichii compared to O. dictynnae, but no difference in green receptor-specific contrast or brightness. Our results show that male choice is guided by the chromatic contrast of the perianth during the initial flower approach but is not affected by the presence of a labellum pattern. Instead, we hypothesise that the labellum pattern is involved in aversive learning during post-copulatory behaviour and used by the orchid as a strategy to increase outcrossing.

中文翻译：

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蜜蜂传粉者对两种性欺骗性 Ophrys 物种的视觉区分。

几乎兰属的所有物种Ophrys被欺骗性授粉。兰花模仿接受性雌性昆虫（主要是膜翅目昆虫）的性信息素，以吸引寻求交配的雄性昆虫。大多数Ophrys物种具有消色差的花朵，但有些具有彩色花被和明亮、显眼的唇瓣图案。我们最近表明，Ophrysheldreichii花的粉红色花被增加了其传粉者（长角蜜蜂Eucera berlandi 的雄性）的可检测性。在这里，我们测试了一个假设，即明亮、复杂的唇瓣图案模仿传粉者的雌性以增加对雄性的吸引力。在一项双重选择测试中，我们为E. berlandi雄性提供了一个O.heldreichii花和来自O. dictynnae的花，它也表现出粉红色的花被，但没有明显的唇瓣图案。两朵花都放在透紫外线的丙烯酸玻璃盒中，以排除嗅觉信号。与O. dictynnae花相比，雄性明显更喜欢O.heldreichii。在第二个实验中，我们用粉红色卡片制成的相同人造花被替换了两朵花的花被，这样两种花刺激物之间只有唇瓣不同。然后雄性在两种刺激之间随机选择，这表明唇瓣模式的存在不会影响他们的选择。光谱测量显示与O.heldreichii花被背景的颜色对比度更高与O. dictynnae相比，但绿色受体特异性对比度或亮度没有差异。我们的结果表明，雄性的选择受初始开花过程中花被颜色对比的指导，但不受唇瓣图案存在的影响。相反，我们假设唇瓣模式涉及交配后行为期间的厌恶学习，并被兰花用作增加异交的策略。