In an attempt to better understand the mechanism underlying lateral collision avoidance in 7 flying insects, we trained honeybees (Apis mellifera) to fly through a large (95cm-wide) flight 8 tunnel. We found that depending on the entrance and feeder positions, honeybees would 9 either center along the corridor midline or fly along one wall. Bees kept following one wall 10 even when a major (150cm-long) part of the opposite wall was removed. These findings 11 cannot be accounted for by the 'optic flow balance' hypothesis that has been put forward to 12 explain the typical bees' 'centering response' observed in narrower corridors. Both centering 13 and wall-following behaviours are well accounted for, however, by a mechanism called the 14 lateral optic flow regulator, i.e., a feedback system that strives to maintain the unilateral optic 15 flow constant. The power of this mechanism is that it would allow the bee to guide itself 16 visually in a corridor without having to measure its speed or distance from the walls.