Lacking stereoscopic vision, bees have evolved another technique to ensure that they land safely.

Credit: EMILY BAIRD/LUND UNIV.

Emily Baird of Lund University in Sweden and her colleagues discovered that honeybees (Apis mellifera ligustica; pictured) alight safely by controlling the rate at which their landing zone expands in their field of vision. Keeping this 'optic flow' constant means that bees slow down as they near their targets.

Baird's team discovered this technique by studying bees as they landed on vertical discs with a rotating spiral pattern. Optical illusions that slowed down or sped up the apparent optic flow caused bees to change their flight speeds accordingly. Rather than landing, many bees would either crash into the spiral or hover in front of it.

This simple method of adjusting speed for landings could be widespread among animals and might even be useful in flying robots in the future, the authors suggest.

Proc. Natl Acad. Sci. USA http://doi.org/psp (2013)