Go with the flow : visually mediated flight control in bumblebees

Despite their small brains and tiny eyes, flying insects are capable of detecting and avoiding collisions with moving obstacles, and with remarkable precision they navigate through environments of different complexity. For this thesis, I have investigated how bumblebees use the pattern of apparent image motion that is generated in their eyes as they move through the world (known as optic flow), in order to control flight. I analysed the speed and position of bumblebee (Bombus terrestris) flight trajectories as they negotiated arenas of different dimensions and visual complexity. I also investigated the impact of optic flow on bumblebee learning flights, a special kind of flight designed to memorise the location of the nest or a newly discovered food source. The general aim of my research has been to understand how flying insects use vision to actively control their flight. The viewing angle at which optic flow is measured has important consequences for flight in densely cluttered environments, where timely control of position and speed are necessary for effective collision avoidance. I therefore investigated when, and how, bumblebees respond to sudden changes in the magnitude of optic flow. My results reveal that the visual region over which bumblebees measure optic flow is determined by the location in the frontal visual field where they experience the maximum magnitude of translational optic flow. This strategy ensures that bumblebees regulate their position and speed according to the nearest obstacles, allowing them to maximise flight efficiency and to minimise the risk of collision. My results further demonstrate that, when flying in narrow spaces, bumblebees use optic flow information from nearby surfaces in the lateral visual field to control flight, while in more open spaces they rely primarily on optic flow cues from the ventral field of view. This result strengthens the finding that bumblebees measure optic flow for flight control flexibly in their visual f