Meeting Abstract
The halteres of flies, heralded as biological gyroscopes, have an enigmatic evolutionary history. Though halteres are derived from wings, the mechanisms favoring this transition are unclear. While flapping halteres encounter large inertial forces and produce negligible aerodynamic forces, flapping wings both experience and produce large inertial and aerodynamic forces. Additionally, recent studies have shown that inertial forces on insect wings could convey sensory information about body rotations via a gyroscopic mechanism similar to halteres. However, the scaling of inertial to aerodynamic forces that wings encounter during complex body trajectories remains an open problem. Thus, we ask how body rotation rate, wing shape (span and outline), and wingbeat frequency interact to determine the inertial and aerodynamic forces on an insect wing. To understand the origins of gyroscopic sensing, we focused on the relative magnitude of the Coriolis force experienced by flapping wings. Using Lagrange’s equation combined with aerodynamic blade element methods, we modeled inertial and aerodynamic forces on flapping wings during a constant orthogonal body rotation. We used wingbeat frequencies, wing shapes, and body rotation rates that correspond to experimentally measured values for a range of insect taxa. Our results show that the ratio of Coriolis to aerodynamic forces decreases from 40% for model moth wings to 0.4% for model fly wings. We also find that wing shape is an important determinant of the relative importance of inertial to aerodynamic loads. These results point to a mechanism that can drive selection for angular rate detection in insect wings and explain their increased specialization for haltere geometries.
