Wing wear, aerodynamics and flight energetics in bumblebees (Bombus terrestris):: an experimental study

I. Previous work has shown that wing wear increases mortality rate in bumblebees. Two proximate explanations have been suggested to account for this: increased energy flight costs and increased predation risk due to reduced manoeuvrability. 2. Wing wear was mimicked by experimentally clipping the forewing distal trailing edge, causing a 10% wing area reduction. Experimental and sham control bumblebees were induced to hover in a flight respirometry chamber for measuring metabolic rate of hovering. Simultaneous video and sound recordings were taken for wingbeat kinematic data required for an aerodynamic analysis. 3. In the experimental group with reduced wing area we measured increased wingbeat frequency, lift coefficient and induced power, but a reduced profile power. The mechanical power output, assuming perfect elastic storage in the flight system, remained largely unchanged after the wing-trimming treatment. 4. Metabolic flight costs (CO2 production rate) did not increase significantly in the reduced wing area group, which is in line with the aerodynamic power output. 5. Our results indicate that an increase of flight cost due to wing wear is not a likely explanation for increased mortality rate in bumblebees. Wing wear may, however, affect escape performance from predators.