Meeting Abstract

50.6  Saturday, Jan. 5  Flight biomechanics in the wild: Environmental turbulence and rolling instablities in foraging orchid bees COMBES, S.A.*; PALEN, W.J.; DUDLEY, R.; Harvard University; Simon Fraser University; U.C. Berkeley scombes@oeb.harvard.edu

Tropical orchid bees cover vast distances at high flight speeds, foraging for scattered resources. Although this long-distance foraging is central to feeding, mating and nest-building behaviors, very little is known about the mechanical challenges of fast, forward flight or the effects of environmental turbulence on flight performance. To understand how bees achieve and maintain high flight speeds during foraging, we studied fast, forward flight in wild orchid bees (Euglossa imperialis) flying in front of an outdoor, open-ended wind tunnel in Panama. We attracted bees to the mouth of the tunnel with aromatic oils and filmed bees with high-speed video cameras. We found that bees begin to roll from side to side when flight speeds reach 3-4 m/s and these rolling instabilities ultimately limit flight speed to about 6 m/s, although individual bees vary widely in their maximum speed. To counteract these rolling instabilities, bees extend their enlarged hindlegs below their bodies, despite the fact that this behavior increases body drag and power expenditure by approximately 30%. To determine how air turbulence contributes to these instabilities, we used a 3-D sonic anemometer to measure turbulence in front of the wind tunnel and compared this to the aerial environment bees encounter at various heights within the forest. We found that the level of turbulence produced by the wind tunnel is comparable to what bees experience in the wild when flying through the mid-canopy. Thus, instability may be one of the primary challenges that bees face in natural, turbulent environments, and an individual bee�s ability to maintain mechanical stability during forward flight could affect foraging range, survival and reproductive success.