COMPARISON OF COLD-HARDINESS IN 2 LADYBIRD BEETLES (COLEOPTERA, COCCINELLIDAE) WITH CONTRASTING HIBERNATION BEHAVIOR

The cold hardiness of two ladybird species from the Czech Republic, Co ccinella septempunctata and Semiadalia undecimnotata, was measured in terms of their supercooling point (SCP) and survival at subzero temper atures. The SCP was lower in diapausing beetles in late summer than in active beetles, and the SCP of diapausing beetles decreased slowly un til mid-winter. The SCP of S. undecimnotata, which overwinters exposed to air, was lower (to -19-degrees-C), that of C septempunctata, which overwinters at ground level insulated in plant material, was higher ( to -15-degrees-C). The SCP of C septempunctata, exposed to extreme flu ctuations of temperature in an outdoor insectary, decreased to -21-deg rees-C. After the termination of diapause, the SCP of C. septempunctat a from natural hibernacula increased in the later part of the cold per iod. In contrast, the SCP of S. undecimnotata and C septempunctata in an outdoor insectary remained low until spring. The cost of being more cold-hardy is possibly compensated for by a low mortality from fungal disease.