In situ mechanical behavior of locust wings related to chitin fiber orientation and distribution

Insect wings are remarkably stable lightweight structures that endure the loads of millions of flapping cycles during flight. The insect wings are built of cuticle, a biological composite material of proteins and embedded reinforcing chitin fibers. A wing is structured as a thin cuticular membrane reinforced by tube-shaped longitudinal and cross veins, which subdivide the wing membrane into polygonal so-called cells. Previous experiments using scanning X-ray micro- and nanodiffraction focused on the distribution and orientation of chitin nanofibers in unloaded wing sections. In the membrane, the chitin fibers were oriented longitudinally far from the veins and, surprisingly, perpendicular to the veins in their vicinity. From these results we propose a specific reinforcement of the wing cells to the tensile loads acting on them during flapping flight. In the proposed experiments, this hypothesis will be tested by stretching different sections of a wing in situ under load control.