The pattern of dispersion of an outdoor population of the smoky brown cockroach, Periplaneta fuliginosa from a tree-hollow harborage

During August and September, the author studied a group of Periplaneta fuliginosa (smoky brown cockroach) adults that appeared in a tree hollow in the evenings and thereafter moved outside the hollow. This suggested that a similar pattern of appearance, dispersion from, and return to the hollow could be repeated every night during their active season. This may cause some of them to move into human habitation. Their dispersion from the wood hollow began at sunset and continued for about 30 minutes. A similar trend was observed among the nymphs. Ten to twenty adults were seen at a time to be climbing up onto the surface of the wood trunk during the initial dispersion. Some adults flew away from higher parts of the tree, especially in early August when the temperature was higher than 31°C. Adults were seen thereafter on the surface of fallen leaves piled on the ground as well as on the surface of a neighboring stone wall and tree trunks around midnight. By about one hour before daybreak, the cockroaches were sighted rather infrequently, although some were seen very close to the tree and re-entering the hollow.