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A Temperature-Induced Switch From Diffusive to Convecttve Ventilation in the Honeybee


It is known that many insects emit CO2 in widely spaced ‘bursts’ or discontinuous 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, convective ventilation regimes. Increasing temperature abruptly switched the dynamics of ventilation from diffusive and continuous (≤11 °C) to convective and discontinuous (>12°C). The ventilation cycle frequency was 7.84mHz and CO2 output per ventilation event (burst phase) was 1.56μl: neither variable was temperaturedependent 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.