The stridulatory movements of acridid grasshoppers recorded with an opto-electronic device

Summary

• (i) The singing movements of acridid grasshoppers are recorded opto-electronically: a small retroflective “Scotchlite” sheeting (Ø2mm) is attached to the tip of the stridulating femur and illuminated via a semi-transmissive mirror mounted at 45° to the optical axis in front of a photographic object lens. The light retroflected through this mirror is focused by the lens on the surface of a position-sensing photo-detector from which the co-ordinates of the light spot are tapped off instantaneously. Using this principle and having one recording device on each side the stridulatory movements of both hindlegs are monitored simultaneously.

• (ii) The grasshoppersChorthippus biguttulus (L.) andChorthippus mollis (Charp.) and their hybrids are studied by this method. Each of the two hindlegs performs a different Stridulatory pattern, the movements being considerably phase-shifted. The legs change their patterns from time to time. In the pure species the two patterns are very tightly coupled. Although in the hybrids in principle the same close relationships exist between the two lateral sub-systems, the couplings of the two patterns can be temporarily loosened. In the extreme, one hindleg may stridulate aCh. mollis song-pattern, whereas the other produces aCh. biguttulus pattern.