9 The Neuromechanics of Fly Flight Control

Abstract

Santiago ramón y cajal may be more widely recognized for his neuroanatomical analyses of the vertebrate cerebellum, hippocampus, cortex, tectum, and retina, but he considered the insect visual system the most magnificent and complex of the myriad systems he had seen (Cajal and Sanchez 1915). The structural sophistication that Cajal identified in the visual system provides much of the functional capacity to control arguably one of the most successful behavioral adaptations in the history of life—insect flight. The enormous success of flying insects, with species numbers estimated in the tens of millions, is highlighted by their ability to migrate vast distances, cope with varying and diverse sensory landscapes, and therefore occupy virtually every terrestrial habitat on the planet (Dudley 2000). From a proximal viewpoint, the “neuroengineering” of insect flight has piqued the curiosity of scientists for decades. An often repeated justification for studying the neurobiology of insect flight control is to understand the very high performance levels characterized by visual, mechanosensory, musculoskeletal, and olfactory systems, all controlled by a brain size on the order of 100 μm³ (Rein et al. 2002).

A neuroscience perspective on fly flight requires an appreciation for the tightly coupled biomechanical events and behavioral strategies that are orchestrated by the brain. In normal free-flight conditions, the visual and mechanosensory systems serve to maintain a stable heading and to compensate for aerodynamic perturbations to the wings and body. These equilibrium and course control systems are modified by olfactory cues to bias the flight path toward food...