Abstract
The annual number of generations of the bean bug, Riptortus clavatus THUNBERG was estimated from rearing results with dried soybean seeds under various temperature and photoperiod conditions. The developmental zero and the effective accumulative temperature were calculated as 12.2°C and 107.6 day degrees, respectively, for the egg stage and 13.3°C and 326.8 day degrees, respectively, in the stage from egg to adult emergence. Individuals which were reared under a photoperiod of 11hr photophase and 13hr scotophase (11L-13D) at 25°C did not lay eggs and their ovaries did not develop. On the other hand, when they were reared under 16L-8D, all of them laid eggs and developed mature ovaries. 45.5% of female bugs reared under 13.5L-10.5D laid eggs. From these results, critical day length was considered to be about 13.5hr. Adults and the 5th instar responded to photoperiod for terminating or inducing diapause. Number of generations a year was estimated to be three from these results. However, two generations a year are possible in the natural conditions, depending on diet sufficiency.
