EFFECT OF TEMPERATURE ON PHOTOPERIODIC RESPONSE IN A SELECTED NONDIAPAUSE STRAIN OF PYRRHOCORIS-APTERUS (HETEROPTERA)

The artificially selected 'non-diapause' strain of Pyrrhocoris apterus (L.) (Heteroptera) showed no diapause response to photoperiod at 26 d egrees C (Socha & Hodkova, 1994). However, the diapause response to sh ort-day photoperiod (LD 12:12 h) became apparent at lower temperatures of 17 degrees C (70% diapause) or 20 degrees C (41% diapause), Diapau se was induced in 60% females by short-day photoperiod combined with t hermoperiod of 26/16 degrees C, whereas only 20% diapause was induced by the same thermoperiod under continuous darkness. Thus the time-meas uring system was not removed by artificial selection but the diapause response was shifted to lower temperatures, The diapause response to s hort days seems to be favoured rather by low temperature during scotop hase than by low temperature throughout the whole light/dark cycle. If the percentage of diapause at 26 degrees C is compared in F-1 hybrids and in wild and selected parental strains the diapause appears to be dominant at LD 13:11 h but recessive at LD 11:13 h and LD 10:14 h, A h ypothesis is proposed that the inheritance of the percentage of diapau se in F1 hybrids is determined by interactions of genes controlling th e temperature dependence of photoperiodic response.