Seasonal Life Cycle of Aelia fieberi (Hemiptera: Pentatomidae) in Relation to the Phenology of Its Host Plants

Adults and nymphs of Aelia fieberi Scott were observed on grasses in the field in Osaka, Japan, from April to August. This species produced 2 generations a year and adults of the 2nd generation entered diapause in August. At 25°C in tbe laboratory, adults raised under long-day conditions reproduced promptly after ecdysis, whereas those raised under short-day conditions entered diapause. The critical daylength was 14.5 h, which corresponds in Osaka to the length of early-August days, including twilight. However, seeds of grasses were available consistently in the field from April to October, and temperatures were high enough for nymphal development even after August. When eggs were kept under outdoor conditions, nymphs developed to adults on a favorable food after August, and the bugs survived until the next spring. Nymphs reared at 25°C in the laboratory reached adulthood on seeds of grasses available in the field from spring to summer, although all nymphs died on seeds produced in summer. The relatively long critical daylength inducing diapause in August prevents reproduction of the 2nd generation which would face the lack of favorable food in autumn.