Abstract
In order to verify the stages of the life history in which 4 species of cockroaches, B. germanica, P. americana, P. fuliginosa, and P. japonica should encounter the winter under unheated conditions in Central Japan, effects of 3 temperature-photoperiod combinations upon the development and reproduction of the cockroaches were investigated. The results seem to indicate that, under unheated conditions in Central Japan, most of newly hatched nymphs of the Periplaneta species will not become adult in the same year, and all developmental stages may encounter the winter, though the retardation of development in the second and/or final instar of Periplaneta species seems to restrict the stage distribution of winter populations of the species mainly to these instars. The results also suggest that a "two-year life cycle" may be rather normal, especially in P. japonica, under outdoor conditions. In B. germanica, adults and nymphs of older instars seem to be the major stages which encounter the winter.
