Flight motor pattern in flying and non-flying Phasmida

Summary The insect order Phasmida comprises species with a broad spectrum of wing morphism and flight ability. By monitoring the electrical activity of several pterothoracic muscles the motor output during tethered flight was recorded for several Phasmida, ranging from excellent fliers to non-winged species. Both winged and non-winged species can generate a motor pattern as judged by criteria used to identify the locust flight pattern. However, in non-fliers the probability of expressing this pattern, its duration and precision are reduced. The antagonistic activity of the chosen muscle pairs is clearly different from the motor output during leg movements, which argues for specific motoneuronal coordination released for different behavioural performances. The demonstration of flight motor output in all tested Phasmida indicates that neural structures including their functional connectivity can be maintained independently of the appropriate peripheral structures. With respect to evolution this supports the idea that central neuronal interactions can be more conservative compared to changes in the periphery. Abbreviations of species names and indication of sexes are given in the first paragraph of Results