Global solar radiation as the factor controlling induction of diapause in the pod midge (Dasyneura brassicae Winn)

In this paper we examine the hypothesis that diapause induction in the polyvoltine pod midge Dasyneura brassicae Winn. (Diptera: Cecidomyiidae) is controlled by cumulative global solar radiation during the larval stage. The correlation between field observations of relative diapause for 3 years and four environmental factors (daylength, temperature, cumulative daylight time, and cumulative global solar radiation) was investigated. The cumulative global solar radiation during the larval stage clearly showed the strongest correlation with the observed relative diapause. It was estimated that larvae which cumulated less than 71.1 kWh m(-2) entered diapause. Compared to former theories on diapause induction in insects, this hypothesis explains ho iv temperature and light can function together and, furthermore: it removes the requirement for biological clock involvement in diapause induction in insects.