CONTROL OF DIAPAUSE AND SUPERCOOLING BY THE RETROCEREBRAL COMPLEX IN PYRRHOCORIS-APTERUS

Effects of external (photoperiod, temperature) and internal (retrocere bral complex, diapause condition) factors on supercooling were studied in Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) adults. An i ncrease in supercooling capacity is associated with the induction of d iapause by short-day photoperiod or cardiacallatectomy of long-day non -diapause insects in spite of a high temperature of 26 degrees C. The induction of diapause is a prerequisite for a further increase in supe rcooling capacity by cold acclimation. Post-diapause adults show low v alues of the supercooling point also in late January or early February , although their developmental potential is fully restored. Evidently the ability to supercool associated with diapause induction is maintai ned by a low ambient temperature in spite of diapause termination. The supercooling point increases rapidly when these adults are transferre d to a high temperature of 26 degrees C and cold re-acclimation is the n no longer possible. The inhibition of morphogenesis (maturation of g onads) by cardiacallatectomy does not prevent the supercooling point f rom increasing in post-diapause adults at the high temperature.