VANCE, Jason T.; ALTSHULER, Douglas L.; DICKINSON, Michael H.; ROBERTS, Stephen P.; Univ. of Nevada, Las Vegas; California Institute of Technology; California Institute of Technology; Univ. of Nevada, Las Vegas: High-speed kinematic analysis of honey bees (Apis mellifera) hovering in variable density atmospheres: Insights into aerodynamic reserve capacity and performance limitations
For flying insects, behaviors such as load carriage, flight at altitude and rapid ascension require the production of aerodynamic forces beyond what is required for simple hovering. However, the mechanisms by which force production is augmented during such behaviors are poorly understood. In this study we measured the kinematics of hovering honey bees using three high-speed digital cameras filming at 6000 fps. Hovering flights in air (21% O2, 79% N2) were compared to flights in heliox (21% O2, 79% He), a normoxic mixture with 1/3 the density of sea-level air. Compared to bees hovering in air, those in heliox had significantly greater wing stroke amplitude, with differences in both ventral and dorsal displacement. Wingbeat frequency did not change between treatments, but the increase in stroke amplitude resulted in a large increase in wingtip velocity and rotational velocity. Because aerodynamic forces scale with the square of velocity, the responses of honey bees to heliox likely enhances lift during both wing translation and rotation. During hovering in heliox, wings often contacted at the dorsal stroke transition; however, it is unknown whether this phenomenon imparted a �clap-and-fling� mechanism of lift production, as has been suggested for smaller insects. Finally, the wings themselves were not planar throughout the entire stroke and were markedly deformed at the stroke transitions. It is unclear how such deformation affects lift or the applicability of traditional aerodynamic models.
