The phenomenon of hydrophobicity of insect cuticles has received great attention from technical fields due to its wide applicability to industry or medicine. However, in an ecological/evolutionary context such studies remain scarce. We measured spatial differences in wing wettability in Lestes sponsa (Odonata: Lestidae), a damselfly species that can submerge during oviposition, and discussed the possible functional significance. Using dynamic contact angle (CA) measurements together with scanning electron microscopy (SEM), we investigated differences in wettability among distal, middle and proximal wing regions, and in surface nanostructures potentially responsible for observed differences. As we moved from distal towards more proximal parts, mean values of advancing and receding CAs gradually increased from 104° to 149°, and from 67° to 123°, respectively, indicating that wing tips were significantly less hydrophobic than more proximal parts. Moreover, values of CA hysteresis for the respective wing parts decreased from 38° to 26°, suggesting greater instability of the structure of the wing tips. Accordingly, compared with more proximal parts, SEM revealed higher damage of the wax nanostructures at the distal region. The observed wettability gradient is well explained by the submergence behaviour of L. sponsa during underwater oviposition. Our study thus proposed the existence of species-dependent hydrophobicity gradient on odonate wings caused by different ovipositional strategies.

昆虫角质层的疏水性现象由于其在工业或医学上的广泛应用而备受技术领域的关注。然而，在生态/进化背景下，此类研究仍然很少。我们测量了Lestes sponsa机翼润湿性的空间差异（Odonata：Lestidae），一种在产卵过程中可能会淹没的豆娘种，并讨论了可能的功能意义。使用动态接触角（CA）测量和扫描电子显微镜（SEM），我们研究了远端，中间和近端机翼区域之间的润湿性差异，以及可能导致观察到差异的表面纳米结构。当我们从远端向更近端移动时，前进和后退CA的平均值分别从104°逐渐增加到149°，从67°逐渐增加到123°，这表明翼尖的疏水性明显低于更多近端部分。此外，各个机翼部分的CA滞后值从38°降低到26°，表明机翼末梢结构的不稳定性更大。因此，与更多的近端部分相比，SEM显示远端区域的蜡纳米结构受到更大的破坏。观察到的润湿性梯度可以很好地解释为水下产卵期间的L. sponsa。因此，我们的研究提出了由不同产卵策略引起的卵形翅上物种依赖性疏水梯度的存在。