Effects of Photoperiod and Temperature on Larval Development and Summer Diapause in Two Geographic Ecotypes of the Rice Stem Maggot, Chlorops oryzae MATSUMURA (Diptera: Chloropidae)

Abstract

Summer diapause in mature third-stadium larvae of Chlorops oryzae MATSUMURA was controlled by a quantitative photoperiodic response. When eggs were kept under LD15:9. pupation in the Akita strain (bivoltine, 39°N) was synchronized under both short and intermediate days with a larval stage of about 14 days. Under LD15:9 at 23°C, the complete larval stage was 68 days because the mature larval stage lasted 40 days. In contrast, the larval stage in the Aichi strain (trivoltine, 35°N) was 14 and 16 days under LD12:12 and 15:9, respectively. Under LD 14.5:9.5 at 23°C, the larval stage was 60 days including the mature larval stage of 40 days. The critical photoperiod for the induction of summer diapause in both strains was shortened with increasing temperature. Photoperiod from LD14:10 to 15.5:8.5 in the egg stage did not influence the quantitative photoperiodic responses of either strain. C. oryzae entered a winter diapause in the first stadium when the egg stage was exposed to LD12:12 but the diapause was terminated by intermediate and long days in the larval stage. There was no clear influence of photoperiod on larval development in either strain after the termination of winter diapause.