Abstract
The histology of the dermal epithelia under the caudal tergites and cerci of the cockroaches, Periplaneta fuliginosa, P. japonica, and P. americana were examined comparatively in regard to the developmental, density-dependent and interspecific differences in the amount of their viscous secretion. In the nymphs of P. fuliginosa and P. japonica, hypodermal tissues under the 6th and 7th tergites and dorsal cuticle of cerci, on which the viscous secretion is accumulated, were found to be much thicker than their 5th tergite. The posterior edge of each tergite is bent upward. These thickened tissues consist of outer smaller cells and large glandular cells filled with granules. On these secretory cuticles, many small pores were observed to pierce through the cuticles, and occasionally connect with ductlike structures meandering around the cells. In the nymph of P. americana, on the other hand, the glandular cells occur in far less numbers under the 6th tergite and the thinner dorsal hypodermis of cerci. All adults of either sex have a single layer of epidermal cells under the 6th and 7th tergites and dorsal cuticles of cerciinstead of the stratified glandular cells. The morphology of the secretory cells of nymphs of P. fuliginosa and P. japonica in gregarious rearings showed no change from that in solitary rearings.
