The female of subsocial shield bug, Parastrachia japonensis (Heteroptera: Cydnidae) provides many drupes of the host tree for its nymphs. Our previous study revealed that female bug foraged tortuously until it had encountered a ripe drupe and the homing bug brought it back to its burrow directly. We here investigated the progressive change of her homing navigation comparing the several behavioural elements at the earlier and later periods during its provisioning season. The 'homing direction', the angles between the longitudinal axis of the bug dragging a drupe and the burrow direction, was measured and showed no apparent difference between the two periods. On the way to home, the bug suddenly stopped at the 'searching point' and changed its directional walking behaviour. The distance between the 'searching point' and its burrow was constant whole through the provisioning season. However, the 'homing speed' of the directional homing was slightly increased in the later homing. In addition, the 'searching time', the walking time from the 'searching point' to its burrow entrance, decreased in the later homing. These results indicate that the particular behavioural elements taking at the two different homing navigation stages in the P. japonensis are progressively changed during provisioning period.
