Electron Microscopic Analysis of Wing Nanopillar Formation in a Dragonfly and a Cicada

Insect wings often bear dense arrays of nanoscale protrusions known as nanopillars that confer functions such as water repellency, self-cleaning, and antibacterial activity. However, how these cuticular nanostructures develop remains poorly understood. Here, I investigate the development of wing nanopillars in the dragonfly Anax parthenope and compare it with that in the cicada Hyalessa maculaticollis. Using electron microscopy, I examined the formation of the wing surface from early cuticle deposition to post-ecdysial stages. In the dragonfly, the wing surface remained smooth throughout cuticle formation and nanopillars appeared only several hours after ecdysis, indicating that they likely arise through physicochemical self-organization of wax-based lipids secreted onto the wing surface. In contrast, nanopillars were already present on pharate wings of the cicada, indicating that they form before ecdysis, although the precise timing and mechanism remain unresolved. These findings show that superficially similar nanostructures on insect wings can differ in developmental timing and may arise through different developmental routes, highlighting the diversity of mechanisms underlying cuticular surface patterning.