Eur. J. Entomol. 90 (4): 465-470, 1993
Comparison of cold hardiness in two ladybird beetles (Coleoptera: Coccinellidae) with contrasting hibernation behaviour
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The cold hardiness of two ladybird species from the Czech Republic, Coccinella septempunctata and Semiadalia undecimnotata, was measured in terms of their supercooling point (SCP) and survival at subzero temperatures. The SCP was lower in diapausing beetles in late summer than in active beetles, and the SCP of diapausing beetles decreased slowly until mid-winter. The SCP of S. undecimnotata, which overwinters exposed to air, was lower (to -19°C), that of C. septempunctata, which overwinters at ground level insulated in plant material, was higher (to -15°C). The SCP of C. septempunctata, exposed to extreme fluctuations of temperature in an outdoor insectary, decreased to -21°C. After the termination of diapause, the SCP of C. septempunctata from natural hibernacula increased in the later part of the cold period. 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.
Keywords: Cold hardiness, hibernation behaviour, Coccinellidae
Accepted: September 25, 1993; Published: December 30, 1993 Show citation
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