Physiological significance of gravity receptors on larval cephalic cuticle in the silk moth, Antheraea proylei Jolly.

The lateral aspects of larval cephalic cuticle of oak tasar moth, Antheraea proylei, a hybrid between Antheraea pernyi and Antheraea roylei exhibited the presence of gravity receptors in the form of dorsal campaniform sensilla. The distribution pattern and number of dome shaped dorsal campaniform sensilla were found to vary in different larval stages. In the first and second larval stages, 4-5 sensilla were localized near the apex of the lateral aspects of the cephalic cuticle on either side of the head. From the third larval stage onwards, on the other hand, both the right and left lateral aspects of the cephalic cuticle were covered with innumerable dome shaped dorsal campaniform sensilla. The sensilla were found to be arranged in groups of 3 to 5 on the cephalic cuticle with dome-free cuticular portion of about 50-100 µm in length between two adjacent groups of the sensilla. The individual dome shaped dorsal campaniform sensillum was either smooth surfaced or was covered with smaller domes through out the surface. The significance of differences in the number and distribution pattern of the dorsal campaniform sensilla among different larval stages in relation to gravity reception and preferred feeding posture are discussed in the light of available literature.