Data from: Visual approach computation in feeding hoverflies

On warm sunny days female hoverflies are often observed feeding from a
wide range of wild and cultivated flowers. In doing so, hoverflies serve a
vital role as alternative pollinators, and suggested to be the most
important after bees and bumblebees. Unless the flower hoverflies are
feeding from is large, they do not readily share the space with other
insects, but instead opt to leave. We have used high-speed videography
followed by 3D reconstruction of flight trajectories to quantify how
female Eristalis hoverflies respond to approaching bees, wasps and two
different hoverfly species. We found that in 94% of the interactions the
occupant female left the flower when approached by another insect. We
found that compared to spontaneous take-offs, the occupant hoverfly's
escape response was performed at ca. 3 times higher speed (spontaneous
take-off at 0.2 +/- 0.05 m/s compared with 0.55 +/- 0.08 m/s when
approached by another Eristalis). The hoverflies tended to take off upward
and forward, while taking the incomer's approach angle into account.
Intriguingly, we found when approached by wasps that the occupant
Eristalis took off at a higher speed and when the wasp was further away.
This suggests that feeding hoverflies may be able to distinguish these
predators, demanding impressive visual capabilities. Our results,
including quantification of the visual information available before
occupant take-off, provide important insight into how freely behaving
hoverflies perform escape responses from competitors and predators (e.g.
wasps) in the wild.