Preliminary Studies on the Life Table of the Rice Stem Borer, Chilo suppressalis (WALKER) (Lepidoptera : Pyralidae)

Abstract

Preliminary life tables of the rice stem borer, Chilo suppressalis (WALKER), excluding hibernation, were construced from 1973 to 1975 in Akita, northern Japan. The typical life table of the rice stem borer in this area ws as follows. There were two mortality peaks in the first generation. The first was observed in the 1st-instar larvae presumably due to their inbility to bore into the stems. The second which involved parasitism, predation and unknown factors, was in the late larval and pupal stages. In the second genaration, there were three low mortality peaks. The first mortality peak was due to predation of eggs and unsuccessful boring of the 1st-instar larvae. The cause of the second, which occurred at the intermediate larval stage, was unknown. The third was possibly due to the dispersion of larvae from the sampling plots. The good correlation between the percentages of injured leaf sheath and those of dead hearts in the first generation, obtained by KOYAMA (1975a), could be explained by the fact that larval density was relatively stable during the period from early to the intermediate larval stage.