Abstract
It was observed that the pattern of phototactic movements of the silkworm larvae varied as the larval maturity proceeded. In wandering stage, mature larvae showed a phototactic behavior moving their heads from side to side (Fig. 1B), and when offered two light sources, they moved along the mid-line between two sources (Fig. 2) .After gut purge, mature larvae showed phototaxis without the head movement shown in wandering stage (Fig. 1C), and went to one of two light sources straight from the start. The threshold for the phototactic response also varied, and the photosensitivity lowered as the maturity proceeded (Fig.3) . The optical axes and structure of stemmata were examined, and the possibility that the variations of phototactic behavior in the mature stage is connected with the change of visual function by larval-pupal development was discussed.
