Hindleg targeting during scratching in the locust

Area of Science:

• Neuroscience
• Animal Behavior
• Biomechanics

Background:

• Locusts (Schistocerca gregaria) display complex motor patterns, including scratching reflexes.
• Tactile stimulation of the wings typically elicits targeted hindleg scratching movements.

Purpose of the Study:

• To investigate whether locust scratching reflexes adapt to changes in wing position.
• To determine if the targeting of scratching movements is body-coordinate fixed or stimulus-location dependent.

Main Methods:

• Tactile stimulation was applied to locust wings in both folded (resting) and outstretched (flight-like) postures.
• Hindleg scratching responses were observed and analyzed, including the direction and target of the movements.
• Experiments were conducted on intact locusts and also with the isolated metathoracic ganglion to assess central nervous system (CNS) control.

Main Results:

• Locusts scratched accurately when wings were in the resting, folded position.
• When wings were outstretched, locusts continued to scratch at the original body-fixed location, missing the actual stimulus.
• This fixed targeting persisted even when the metathoracic ganglion was isolated, indicating a CNS-based motor program.

Conclusions:

• The targeting of locust hindleg scratching movements towards wing stimulation is fixed relative to body coordinates.
• The reflex does not compensate for altered wing positions, suggesting a lack of online spatial re-calibration for this specific motor pattern.
• This fixed motor program highlights the constraints and specificity of sensory-motor control in insects.