Controlling roll perturbations in fruit flies

TLDR

Aerodynamic instabilities require fast corrective actions for stable flapping flight. The study investigates how flies control roll perturbations, the most unstable and sensitive degree of freedom. A magnet glued to each fly is pulsed to roll it mid‑air, allowing observation of corrective responses. Flies correct roll perturbations up to 100° within 30 ± 7 ms using a stroke‑amplitude asymmetry that follows a linear proportional–integral controller, and for larger perturbations evidence of nonlinear, hierarchical control is seen; responses occur within 5 ms, making it one of the fastest reflexes in animals.

Abstract

Owing to aerodynamic instabilities, stable flapping flight requires ever-present fast corrective actions. Here, we investigate how flies control perturbations along their body roll angle, which is unstable and their most sensitive degree of freedom. We glue a magnet to each fly and apply a short magnetic pulse that rolls it in mid-air. Fast video shows flies correct perturbations up to 100° within 30 ± 7 ms by applying a stroke-amplitude asymmetry that is well described by a linear proportional–integral controller. For more aggressive perturbations, we show evidence for nonlinear and hierarchical control mechanisms. Flies respond to roll perturbations within 5 ms, making this correction reflex one of the fastest in the animal kingdom.