Conspicuous female coloration can evolve through male mate choice or via female‐female competition thereby increasing female mating success. However, when mating is not beneficial, such as in pre‐reproductive females, selection should favor cryptic rather than conspicuous coloration to avoid male detection and the associated harassment. Nevertheless, conspicuous female coloration occurs in many prereproductive animals, and its evolution remains an enigma. Here, I studied conspicuous female coloration in Agriocnemis femina damselflies, in which the conspicuous red color of the immature females changes to a less conspicuous green approximately a week after their emergence. I measured body size, weight, and egg numbers of the female morphs and found that red females are smaller and lighter and do not carry developed eggs. Finally, I calculated the occurrence frequency and mating frequency of red and green females in several populations over a three‐year period. The results demonstrate that red females mated less frequently than green females even when red females were the abundant morph in the populations. I concluded that conspicuous female coloration is likely to function as a warning signal of sexual unprofitability, thereby reducing sexual harassment for females and unprofitable mating for males.

中文翻译：

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雌性生殖前着色减少豆娘的交配骚扰

显着的雌性颜色可以通过雄性择偶或雌性竞争而进化，从而提高雌性交配的成功率。然而，当交配没有好处时，例如在生殖前的雌性中，选择应该偏向于隐秘而不是显眼的颜色，以避免雄性被发现和相关的骚扰。尽管如此，在许多生殖前的动物中都会出现明显的雌性着色，其进化仍然是一个谜。在这里，我研究了 Agriocnemis femina 豆娘中显眼的雌性着色，其中未成熟雌性的显眼红色在它们出现大约一周后变成不那么显眼的绿色。我测量了雌性变种的体型、体重和卵数，发现红色雌性更小更轻，并且不携带发育的卵。最后，我计算了三年期间几个种群中红色和绿色雌性的发生频率和交配频率。结果表明，即使红色雌性是种群中丰富的变体，红色雌性的交配频率也低于绿色雌性。我的结论是，显眼的雌性颜色可能是性无利可图的警告信号，从而减少对雌性的性骚扰和对雄性的无利交配。