A temperature-induced switch from diffusive to convective ventilation in the honeybee

It is known that many insects emit CO2 in widely spaced 'bursts ' or discontinu-ous ventilation events, usually characterized by active abdominal ventilation. We describe the discontinuous CO2 emission characteristics of the honeybee (Apis mellifera ligustica Spinola), and utilize its 'chill coma ' temperature threshold (12°C) to effect transitions from continuous, diffusive to discontinuous, convec-tive ventilation regimes. Increasing temperature abruptly switched the dynamics of ventilation from diffusive and continuous (^11 °C) to convective and discon-tinuous (>12°C). The ventilation cycle frequency was 7.84mHz and CO2 output per ventilation event (burst phase) was 1.56/A: neither variable was temperature-dependent in the range 12-15 °C. The rate of CO2 emission did not change significantly in the range 7-15 °C, possibly owing to increased membrane leakiness at lower temperatures. At 15°C, honeybee metabolic rate (2.69 W kg"1, mean mass 0.094 g) is similar to that of other similarly sized insects capable of significant endothermy