Diapause and Photoperiodic Response in Coccinella septempunctata brucki MULSANT (Coleoptera: Coccinellidae) in Hokkaido, Japan

Abstract

The regulatory function of photoperiod and temperature on the life-cycle of Coccinella septempunctata brucki MULSANT in Hokkaido populations was investigate. Dissection of adults from Sapporo (43°N) in mid-October showed diapausing adults (partly hidden in grass tussocks) possessing enlarged fat body, ovaria without vitellinized oocytes and at a beginning of regression of testicular follicle tissue. Some of the females had sperm in their spermathecae. Experimental rearings under contrasting photoperiods (12L-12D, 16L-8D) and three temperatures (20, 25 and 30°C) of insects sampled in early September, and of their offspring, showed that the Sapporo population gas a long-day photoperiodic response adequate for the induction of winter diapause. This is in contrast to short-day response inducing summer diapause in the Nagoya (35°C) plains, but similar to C. septempunctata septempunctata in France and central and northern Europe, i.e. regions with climate similar to Hokkaido.