Robust flight performance of bumble bees with artificially induced wing wear

Abstract

We lack a mechanism that links wing wear with mortality in foraging social insects. This study tests the hypothesis that wing wear strongly degrades foraging flight performance, thereby providing a biomechanical explanation for the wing wear – mortality relationship. We examine the effect of simulated wing wear — wing area reduction and asymmetry — on the flight behaviour of bumble bee ( Bombus flavifrons Cresson, 1863) workers moving between vertically oriented flowers spaced 30 cm apart and arranged in a two-dimensional horizontal grid. Flight behaviour was measured in three dimensions as total flying distance, mean velocity, variability of velocity, maximum acceleration, maximum deceleration, percentage of time spent accelerating, and displacement from a straight line path between flowers. Loss of wing area had surprisingly little effect on flight behaviour. Viewed multivariately, bees with low asymmetry and low loss of mean area, or with high asymmetry and high loss of mean area, differed from the other three treatment groups. When bees were burdened with both high asymmetry and high loss of wing area, their between-flower flight path was less direct. Overall, flight behaviour of bumble bees was highly resilient to major changes in wing area and asymmetry in this simple foraging environment. The wing wear-associated causes of increased mortality remain elusive.