Impacts of leg, wing, and body collisions on flight performance in carpenter bees

Flying insects often forage among cluttered vegetation that forms a series
of obstacles in their flight path. Recent studies have focused on
behaviors needed to navigate clutter while avoiding all physical contact,
and as a result, we know little about flight behaviors that do involve
encounters with obstacles. Here, we challenged carpenter bees (Xylocopa
varipuncta) to fly through narrow gaps in an obstacle course to determine
the kinds of obstacle encounters they experience, as well as the
consequences for flight performance. We observed three kinds of
encounters: leg, body, and wing collisions. Wing collisions occurred most
frequently (in about 40% of flights, up to 25 times per flight) but these
had little effect on flight speed or body orientation. In contrast, body
and leg collisions, which each occurred in about 20% of flights (1-2 times
per flight), resulted in decreased flight speeds and increased rates of
body rotation (yaw). Wing and body collisions, but not leg collisions,
were more likely to occur in wind versus still air. Thus, physical
encounters with obstacles may be a frequent occurrence for insects flying
in some environments, and the immediate effects of these encounters on
flight performance depend on the body part involved.