PHOTOPERIODIC RESPONSE AND LIFE-CYCLE OF COCCYGOMIMUS-LUCTUOSUS SMITH(HYMENOPTERA, ICHNEUMONIDAE)

The photoperiodic response of two populations of Coccygomimus luctuosu s SMITH, a polyphagous internal parasitoid was investigated In the Hok kaido strain (43 degrees N), diapause was induced in about 90% of indi viduals at the final larval instar under LD12:12 at both 17 and 20 deg rees C, whereas the diapause rate was much lower at photoperiods longe r or shorter than LD12:12. Although the diapause rate was slightly hig her at 17 than at 20 degrees C, the shape of the photoperiodic respons e curve was not altered by temperature. In the Hyogo (35 degrees N) po pulation, neither short nor long photoperiods induced noticeable devel opmental arrest at 20 degrees C, while short photoperiods at 17 degree s C induced diapause in a significant number of individuals. Larvae at the penultimate instar were most sensitive to diapause inducing stimu li. Diapause development continued under short photoperiods and the ra te of diapause termination depended on photoperiod but not temperature . The difference in temperature-dependent photoperiodic response betwe en the two populations might be related to the habitat climate conditi ons (severe north vs mild south). The result clearly indicates that th e regulation of life cycle in C. luctuosus depends on environmental cu es, suggesting 3-4 generations are produced annually in Hokkaido, and 7-8 generations in Hyogo.