Mechanosensory hairs in bumble bees (Bombus terrestris) detect weak electric fields

Bumble bees (Bombus terrestris) use information from surrounding electric fields to make foraging decisions. Electro-reception in air, a non-conductive medium, is a recently discovered sensory capacity of insects, yet the sensory mechanisms remain elusive. Here, we investigate two putative electric field sensors; antennae and mechanosensory hairs. Examining their mechanical and neural response, we show that electric fields cause deflections in both antennae and hairs. Hairs respond with a greater median velocity, displacement and angular displacement than antennae. Extracellular recordings from the antennae do not show any electrophysiological correlates to these mechanical deflections. In contrast, hair deflections in response to an electric field elicited neural activity. Mechanical deflections of both hairs and antennae increase with the electric charge carried by the bumble bee. From this evidence, we conclude that sensory hairs are a site of electro-reception in the bumble bee.