The Effects of Low Temperature on Metabolism and Survival of Individual Honey Bees (Apis mellifera)

Abstract

The honey bee (Apis mellifera) is one of the few insects capable of thermoregulation. Heat regulation of an isolated individual under the low temperature conditions normally seen in a northern temperate winter are investigated in this thesis. The factors examined are twofold: the variation in thermal output with ambient temperature and the survival potential from a cold comatose state. Individual workers attempted to maintain their body temperature through active thermoregulation. Active heating was pronounced and continuous in the range of thoracic temperatures between 19.l-29.3°C. Oxygen consumption, and corresponding heat production, showed a linear increase with a decrease in ambient temperature in the range of T_ambient from 35-12°C (V­_O2 = -2.82 x T_ambient + 96.64, r2 = 0.94). Large increases in oxygen consumption were seen at temperature differences (T_thorax - T_ambient) ? 2.0°C (above the physiologic minimum.) At cabinet temperatures below 12.9°C, the oxygen consumption of individuals did not stabilize, but decreased continuously, representing an abrupt cut-off in metabolic capacity seen at the chill coma point. The survival potential of a comatose honey bee is high, with a 51% survival rate seen over all tests. In general, the number of survivors decreased with exposure time and exposure temperature. For all bees over all tests, chill coma temperature was dependent on exposure time, but was not dependent on exposure temperature. Revival time was found to be dependent on both exposure temperature and exposure time. An individual was most likely to survive chill coma if it revived in less than 4 min and under 18°C with passive exogenous heating.