Seasonal Change in Cold Tolerance of the House Spider, Achaearanea tepidariorum (Araneae: Theridiidae)

Abstract

Field-collected nymphs of Achaearanea tepidariorum displayed significant seasonal variation in the level of cold tolerance. The whole body supercooling point (SCP), the absolute limit of freeze avoidance, was ranged from -8.1°C in August to -20.1°C in January, and the median lower lethal temperature (LLT 50), and indicator of chilling tolerance, from -2.1°C in August to -13.7°C in January. Seasonal depression of LLT 50 began to occur one month earlier than that of the SCP, suggesting that these two changes are induced by separate processes. The cold tolerance strategy in term of the seasonal patterns of SCP and LLT 50 was discussed.