ИСТИНА

Flight speed generally increases with animal body size, but miniature Ptiliidae beetles can fly at speeds and accelerations of closely related Staphylinoidea beetles three times as large. We showed that this performance results from light bristled wings and previously unknown type of wingbeat cycle. We obtained three-dimensional reconstructions of morphology and kinematics in one of the smallest ptiliids, Paratuposa placentis with 395 μm body length, and performed flight mechanics analysis using dynamically scaled models and computational fluid dynamics. Bristled wing of P. placentis is at least 5 times lighter than equivalent membranous wing but at the same time it produces only 25% less aerodynamic force. Motion of bristled wings requires little inertial power, so muscle mechanical power remains positive throughout the wing beat cycle, making elastic energy storage obsolete. Wingbeat trajectory of P. placentis has the shape of a pronounced figure-eight loop that consists of subperpendicular upstroke and downstroke followed by claps at stroke reversals, above and below the body. Computational analyses suggest a functional decomposition of the flapping cycle in two power half strokes producing a large upward force and two down-dragging recovery half strokes. The wings thereby produce high aerodynamic torques that cause the high-amplitude body pitch oscillation. We found that relatively massive elytra function as inertial brakes and enhance posture stability due to unusual high-amplitude movement. This novel flight style evolved during miniaturization may compensate for costs associated with air viscosity and helps explain how extremely small insects preserved superb aerial performance during miniaturization. KKeeyywwoorrddss:: biolocomotion, insect flight, miniaturization, bristled wing, Ptiliidae, Coleoptera