Bristled-wing design of materials, microstructures, and aerodynamics enables flapping flight in tiny wasps

Parasitoid wasps of the smallest flying insects with bristled wings exhibit sophisticated flight behaviors while challenging biomechanical limitations in miniaturization and low-speed flow regimes. Here, we investigate the morphology, material composition, and mechanical properties of the bristles of the parasitoid wasps Anagrus Haliday. The bristles are extremely stiff and exhibit a high-aspect-ratio conical tubular structure with a large Young's modulus. This leads to a marginal deflection and uniform structural stress distribution in the bristles while they experience high-frequency flapping-induced aerodynamic loading, indicating that the bristles are robust to fatigue. The flapping aerodynamics of the bristled wings reveal that the wing surfaces act as porous flat paddles to reduce the overall inertial load while utilizing a passive shear-based aerodynamic drag-enhancing mechanism to generate the requisite aerodynamic forces. The bristled wing may have evolved as a novel design that achieves multiple functions and provides innovative ideas for developing bioinspired engineering microdevices.