Force measurements on locusts during visually-evoked collision avoidance maneuvers

The collision avoidance behavior of the locust, Schistocerca americana, in response to simulated approaching objects, also called looming stimuli, was investigated in a low speed wind tunnel. The animals were mounted using a sting on a sensitive six-component microbalance custom-designed for the experiments. Forces and moments were measured as a function of time during the simulated approach and interpreted in the context of collision avoidance behaviors. The stimuli presented from the side effectively evoked robust and discernible collision avoidance responses. Locusts attempted to avoid collision by either flying over or under the looming object, or alternatively by steering around it. These efforts appeared in the form of changes in aerodynamic forces and moments as a function of time. It was also observed that the locusts increased the wing flapping frequency in response to the stimulus.