Transmission of muscle potentials during free flight of locusts
This paper briefly outlines developments in light-weight telemetry devices, and describes in detail a miniature radio system that transmits muscle potentials from the desert locust, Schistocerca gregaria, in free flight. The device, which is mounted to the insect's prothorax weighs only about 10% of its body's mass, and does not restrict the locust's ability to fly and to manoeuvre normally. When combined with video-monitoring, both normal (=50 Hz) or high-speed frame frequency (up to 500 Hz), the system makes it possible to record the electrical activity of certain muscles (EMG) and to compare this activity with the insect's behavioural performance. Results are presented that show that the electrical activity can be associated with several flight parameters, e.g. flight speed, wing-beat frequency, wing-stroke angles, and rotations about different body axes. The recent advent of even smaller electronic parts has made possible the realisation of multi-channel transmission, and a dual-channel device has been successfully used to simultaneously record two physiological parameters from a flying locust. This device demonstrated the recruitment of bilateral symmetric muscles during yawing or rolling, and allowed the timing of homonomous muscle action to be recorded. Some of the results are novel, and others generally corroborate earlier findings derived from tethered animals. It is expected that further advances in the miniaturisation of electronic components will make telemetry from smaller insects a possibility in the future.
free flight locust radio-telemetry video-monitoring multi-channel recording