Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya Street 123, Moscow 117647, Russia.
Proc Biol Sci. 2012 Dec 12;280(1752):20122391. doi: 10.1098/rspb.2012.2391. Print 2013 Feb 7.
Leafhoppers (Insecta, Hemiptera, Cicadellidae) actively coat their integuments with brochosomes, hollow proteinaceous spheres of usually 200-700 nm in diameter, with honeycombed walls. The coats have been previously suggested to act as a water-repellent and anti-adhesive protective barrier against the insect's own exudates. We estimated their wettability through contact angle (CA) measurements of water, diiodomethane, ethylene glycol and ethanol on detached wings of the leafhoppers Alnetoidia alneti, Athysanus argentarius and Cicadella viridis. Intact brochosome-coated integuments were repellent to all test liquids, except ethanol, and exhibited superhydrophobicity, with the average water CAs of 165-172°, and the apparent surface free energy (SFE) estimates not exceeding 0.74 mN m(-1). By contrast, the integuments from which brochosomes were removed with a peeling technique using fluid polyvinylsiloxane displayed water CAs of only 103-129° and SFEs above 20 mN m(-1). Observations of water-sprayed wings in a cryo-scanning electron microscope confirmed that brochosomal coats prevented water from contacting the integument. Their superhydrophobic properties appear to result from fractal roughness, which dramatically reduces the area of contact with high-surface-tension liquids, including, presumably, leafhopper exudates.
叶蝉（昆虫纲，半翅目，叶蝉科）体表通常覆盖有直径为 200-700nm 的蛋白质空泡状的沫蝉蜡质层，其壁呈蜂巢状。这些蜡层被认为具有防水和抗粘性的保护作用，可以防止昆虫自身分泌物的附着。我们通过测量水、二碘甲烷、乙二醇和乙醇在 Alnetoidia alneti、Athysanus argentarius 和 Cicadella viridis 三种叶蝉的离体翅膀上的接触角（CA）来评估其润湿性。完整的带有沫蝉蜡质层的表皮对所有测试液体均具有疏水性，除了乙醇，且表现出超疏水性，水的平均接触角为 165-172°，表观表面自由能（SFE）估计值不超过 0.74mN m(-1)。相比之下，使用流体聚二甲基硅氧烷通过剥离技术去除沫蝉蜡质层后的表皮，其水的接触角仅为 103-129°，SFE 超过 20mN m(-1)。在低温扫描电子显微镜下观察喷洒水雾的翅膀的实验结果证实，沫蝉蜡质层可以防止水与表皮接触。其超疏水性的特性可能源于分形粗糙度，这极大地减少了与高表面张力液体（包括可能的叶蝉分泌物）的接触面积。
