Use of walking trails by bees

SIR -- Trail use has evolved twice among the ground-dwelling social insects (ants and termites), a striking example of evolutionary convergence in behaviour. The other groups of social insects, bees and wasps, are principally flying organisms, not known to use extended walking trails for locating colony resources, although some species of stingless bees follow scent marks or aerial odour trails during flight [1]. Our field investigation of the Amazonian bumble bee, Bombus transversalis, reveals that it clears and maintains trails on the forest floor, similar in appearance to the recruitment trails of ants [2].