The analysis of orientation behaviour of insects in the virtual odour space.

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The researcher had already built a prototype of a locomotion compensator or servo-sphere apparatus, which compensates all the locomotive activities of a test animal on a sphere, at first in Japan. In this research, the apparatus was developed further to perform virtual reality experiments on insects : to guide a test insect toward a virtual target by the real time control of directional cues, such as wind and odour pulses, in reference to a space model of a cue. If the insect was guided successfully to reach the target, the model is proved to be viable. This requires more precise and rapid control of the sphere than that of the prototype, so not only the hardware but also the software of the apparatus had to be improved. The former part of this research includes engineering solutions of these practical issues, such as, the extension of a driver software for the real time relay control and the planting of GUI control in a track-analysis program. As a result, the apparatus was refined to be a high-speed, high-resolution machine, which enables the controlled exposure for a test insect to an odour stimulus at real time. Then the function of wing-beating performed by a sex-pheromonally stimulated male silkworm moth was investigated on the apparatus. Experimental results on wing-amputated males suggested that the extraction of atmospheric air in front by beating wings could be a principal mechanism for the male to orientate himself toward a pheromone source. Then a virtual odour space was designed to give pheromonal pulsed to a male when he directed toward a virtual target. The male was successfully guided to the target irrespective of his wing condition. The result is believed to prove the viability of a virtual reality experiment for demonstrating a spatial orientation mechanism.