Bees, Flowers and Tribo-bio-electricity*

Electricity is everywhere and is essential to the functioning of life. Understanding how organisms organise themselves using the natural manifestations of electricity is just as relevant as studying vision, smell or hearing [1]. Aquatic animals, such as sharks, rays, some dolphins and electric fish, have been known for quite some time to use electroreception, yet only recently have terrestrial animals been shown to detect weak electric fields [2]. We have discovered that bumblebees can detect and learn about the weak electrostatic field that arises when they approach a flower [2]. Can bumblebees and other arthropods be regarded as soft condensed matter electrified? Flying bees are usually positively charged (30-120 pC), whilst flowers tend to be negatively charged. In addition, the fair-weather vertical atmospheric potential gradient (APG, 100V/m, resulting from atmospheric ionization and the global electric circuit) contributes to this Bee-Plant-Atmosphere interaction. We have found that triboelectrification and weak Coulomb force are together relevant to the sensory biology of bees, other terrestrial arthropods and plants. Detection mechanisms are shown to involve electromechanical coupling of small charged and innervated hairs on the animal’s body. Recently, we showed that host-seeking ticks can be attracted to their vertebrate hosts using electrostatic force [3]. Also, during dispersal, spiders engage in ballooning behaviour,  exploiting the Coulomb force generated by their negative silk threads entering the positive APG, thus generating enough lift to become airborne. This work opens-up the enticing possibility that arthropods, in effect the majority of animal species, are capable of aerial electroreception, a sensory modality, a previously unknown “6^th sense”, that humans seem to lack.