Defensive Behavior of the Cockroaches, Periplaneta fuliginosa SERVILLE and P. japonica KARNY (Orthoptera : Blattidae) in Relation to Their Viscous Secretion

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Abstract
A viscous secretion accumulates on the 6th and 7th tergites and the dorsal surface of cerci in both nymphs of P. fuliginosa and P. japonica when they are reared alone or in a low population density/container. It was scarce in the nymph of P. americana and not in adults of any of these 3 spp. The nymphs of the former 2 spp. with viscous secretion exhibited an active and characteristic defensive behavior against aggressive ants of Formica exsecta fukaii. This was a means of splashing droplets of the secretion over some distance, making ants helpless instantly. The nymph of P. americana, which has no or little secretion, did not exhibit such behavior and was attacked and seriously injured by the ants. The viscous secretion consists principally of a protein, low or lacking in S and contains no noxious component. The dorsal glands had no relation to the secretion. The source of the secretion may be the hypodermal cells corresponding to the viscous regions, since the painting of each of them with a bond completely prevented its accumulation. There were peculiar stout hairs on these secretory regions.