Novel Bristled-Wing Design of Materials, Microstructures and Low-Speed Aerodynamics Enables Tiny Wasps’ Flapping Flight

Parasitoid wasps, one of the smallest flying insects with bristled wings, exhibit sophisticated flight behaviors while challenging biomechanical limitations in miniaturization and low-speed flow regimes. It however remains unclear how the bristled-wing morphologies and biomechanical characteristics, which particularly affect the flight capabilities of these insects, cope with extreme size reductions. 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 novel 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 drag-enhancing mechanism to generate the requisite aerodynamic forces. Thus, an integrated design of materials, microstructures, and low-Reynolds-number aerodynamics enables bristled wings to push the physical boundary of sizing limitations and thereby facilitate flapping-wing flights in parasitoid wasps.