The effect of allatectomy and photoperiod on the supercooling point in <i>Pyrrhocoris apterus</i> adults

Abstract

Abstract Adults of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) reared at 26°C had a considerably lower supercooling point (SCP) in diapause‐inducing (LD 12:12 h) than in diapause‐inhibiting (LD 18:6 h) photoperiodic regimes. Exposure of the insects to diapause‐inducing acclimation conditions (LD 8:16 h and a temperature of 20°C during photophase and 5°C during scotophase) for 2–3 weeks had very little effect on the SCP, irrespective of the rearing photoperiod. Allatectomized adults kept continuously at LD 18:6 h and 26°C had high SCP similar to intact or sham‐operated insects. In contrast to non‐allatectomized insects, the SCP of allatectomized insects decreased after an exposure of from 2 to 3 weeks to diapause‐inducing acclimation conditions (see above) almost to the level found in the intact diapausing insects. The relationship between the decrease of SCP and ‘diapause syndrome’ (de Wilde, 1970) is discussed.