There are many instances of animals being able to sense electrical signals, like sharks, rays and platypuses but there having been new studies showing this ability in insects

The interactions between insects and flowering plants play an important role in pollination and ecology. While bees and other insects depend on the resources provided by the flower, the flower in return relies on the insects for reproduction via pollination. Through this inter-species dependency, flowers have traits which have evolved almost exclusively to attract pollinating bees. Plants have evolved specific chemical and physical structures to produce flower colours adapted to the visual capabilities of their pollinating bees. Another method of pollination that has been observed is through electrostatic force interactions between the flower and its bee. How do electrostatic fields contribute to pollination?

Planet Earth is electrically neutral, but the interior of the Earth is positively charged and the crust carries a negative charge to about 150 kilocoulombs. A flower rooted to Earth accumulates charge, producing its own localized, negatively charged electric field.

An electric field describes the force that a charged particle would experience due to the presence of other charged particles. The structure and pattern of the “floral electric field” is determined by the geometry of the flower. The structure of the electric field at the surface of the flower can be visualized by dusting flower heads with an electrostatically charged coloured powder.  The distribution of coloured powder over the flower structure shows the charge density distribution of the electric field and where there is a higher accumulation of negative charge, there is stronger electric field around this point. We can see charge density accumulates with greater concentration along the edges of the petals, stigma, outlining the geometric shape, stigma, and anthers of the flower. This is due to the effect of charge density at a surface being inversely proportional to the radius of curvature of the surface, meaning a floral electric field paints an electrostatic picture of the flower for its pollinators, from its shape to the location of the stigma.

 

Honeybees are famous for their unique method of communication. Dancing honeybees communicate with their hive by emitting  oscillating electric fields detectable by other honeybees through the joints of their antennae. Bumblebees differ visually form honeybees as they are bigger and covered in fine hair which they use as well as their antennae to detect electrical signals, like a floral electric field as the bumblebee approaches a flower.

A flower may be slightly negatively charged due it being grounded to Earth, but a bee is airborne so how does it become positively charged? When a bee flaps its wings at about 230 times a second, the friction caused by the air, and by the bee’s wings rubbing together, knocks off electrons, allowing the bee to gain a positive charge. This effect of charging due to frictional contact is called the triboelectric effect.

When the positively charged bumblebee approaches a flower, the charge on the bee interacts with the negative charge on the flower, the force generated by the interacting electric fields intensifies. The bee detects this force with its bee hairs and can assess the floral electric signal available from the flower. As the electrostatic forces between the bee and the flower increase with decreasing distance, the potential difference between the bumblebee and flower will induce pollen transfer to the bee from the stigma over a distance of 0.5mm. The electrostatic forces causing the pollen grains to jump through the air also help the pollen to stick to the hairy body of the bumblebee. The electric field force on the pollen grains is more influential than gravity at this close range, and the effects of these forces aid in the bee to stigma or stigma to bee pollen transfer.

Despite these developments in electric ecology, there is a large amount still unknown about the world of insect floral electric interactions and many more interesting aspects to be explored.

 

 

References:

[1] Papiorek, S., Junker, R.R., Alves-dos-Santos, I., Melo, G.A.R., Amaral-Neto, L.P., Sazima, M., Wolowski, M., Freitas, L. and Lunau, K. (2016), Bees, birds and yellow flowers: pollinator-dependent convergent evolution of UV patterns. Plant Biol J, 18: 46-55.

[2] Ivanchin, A. (2017) Electric, Magnetic and Gravitation Field of the Earth. Journal of Geoscience and Environment Protection5, 66-79. doi: 10.4236/gep.2017.512005.

[3] Jacob M. Peters, Nick Gravish, Stacey A. Combes; Wings as impellers: honey bees co-opt flight system to induce nest ventilation and disperse pheromones. J Exp Biol 15 June 2017; 220 (12): 2203–2209. doi: https://doi.org/10.1242/jeb.149476

[4] Greggers et al., “Reception and learning of electric fields in bees,” Proceedings of the Royal Society B: Biological Sciences, vol. 280, no. 1759, May 2013

[5] Clarke D, Morley E, Robert D. The bee, the flower, and the electric field: electric ecology and aerial electroreception. J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2017 Sep;203(9):737-748. doi: 10.1007/s00359-017-1176-6. Epub 2017 Jun 24. PMID: 28647753; PMCID: PMC5599473.

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