Although bees’ brains are incredibly small — just one million neurons compared to humans’ 100 billion — they have remarkable abilities to navigate, learn, communicate, and remember. The next time you hear the low droning sound of a bee in flight, look closer: the bee has navigated to this particular spot for a reason using a fascinating set of tools. She may be using her sensitive olfactory organs, which provide a 3D scent map of her surroundings. She may be following visual landmarks or instructions relayed by a hive-mate. She may even be tracking electrostatic traces left on flowers by other bees. In “What a Bee Knows: Exploring the Thoughts, Memories, and Personalities of Bees,” entomologist Stephen Buchmann explores a bee’s way of seeing the world and introduces the scientists who make the journey possible. In the following excerpt from Chapter 4, “What Bees Sense and Perceive,” learn how bees use electrostatic charges as they forage for nectar. 

Buchmann is a pollination ecologist who specializes in bees and flowers. He is an adjunct professor with the Departments of Entomology and Ecology and Evolutionary Biology at the University of Arizona and a fellow of the Linnean Society of London. He has published nearly 200 peer-reviewed scientific papers and 11 books, including “The Reason for Flowers: Their History, Culture, Biology, and How They Change Our Lives” and “The Forgotten Pollinators,” with Gary Paul Nabhan.

Electrically Charged Bees and Their Flowers

All flying objects, whether they are honey bees, bumblebees, baseballs, or Dreamliner jumbo jets, acquire strong positive electrostatic charges.

This is caused by friction with passing air molecules interacting with their surfaces.The buildup of charge—“static” electricity—on the surface of nonconductors due to friction is called triboelectricity. Think of the time you breezed across a wool carpet barefoot only to be zapped and surprised when you touched (discharged) on a metal doorknob.

Worker honey bees acquire electrostatic charges with a strength of up to several hundred volts during flight. Once they alight, these charges dissipate and may bleed off onto leaves, flowers, or other objects they rest or walk upon. Flowering plants are negatively charged, literally grounded and living in one place for their entire lives. Plants typically bear flowers at or near their growing tips, and these tips develop the strongest negative charges over an entire plant’s surface. Positively charged flying bumblebees and likely other bees can detect the negative charges on flower surfaces.³⁷ Across their petals, stamens, and styles, flowers possess fine patterns of differing electrostatic charges.

These floral electrostatic patterns were first detected in 2014 by researchers using specialized detection and measurement techniques to study bumblebees.³⁸ In these studies, samples of common garden flowers (Lilium, Gerbera, Narcissus, Bergenia, and Petunia) were sprayed with electrostatically charged colored powders. These microscopic powders stuck fast to places that were more highly charged than neighboring areas. This simple visualization technique gave the researchers a unique glimpse into a hitherto unknown realm of flower physics and what bees could perceive. These same authors found that a stem 30 centimeters (11.8 inches) tall with a flower in a normal (100 volt/meter) atmospheric electric field would have a 30-volt difference between the flower and the neighboring air.

Later, Dominic Clarke and her team tested bumblebees to determine if they could detect and respond to these low-voltage electrical patterns. They found that artificially induced electric fields moved the filiform hairs (mechanoreceptors) on the heads and bodies of bees. Their deflections sent signals to nerves and ultimately to the brain, allowing the bees to sense charge differences on and within flowers. When a bumblebee lands on a flower, some of her positive charge bleeds off her hairy body and moves to the flower. This cancels some of the flower’s negative charge. Thus, the bee leaves her electrostatic footprints on the flower’s petals. Bumblebees can detect and learn to discriminate between charged and uncharged artificial flowers in the laboratory.

In one such study, bumblebees were trained to fly into a device called a Faraday pail, which measured their electrostatic charges, to receive a sugar reward. Next, the bees were trained to visit Petunia flowers. Landing bees changed the electrostatic field on the flowers by about twenty-five millivolts, and these effects lasted for roughly one hundred seconds. But while present, they gave the blossom an altered signature that other bees could detect and respond to.³⁹

In effect, the bees are labeling their empties. Later, foraging bees that land on these electrically labeled flowers can tell that they were previously visited by another bee and likely contain little or no nectar.

In effect, the bees are labeling their empties. Later, foraging bees that land on these electrically labeled flowers can tell that they were previously visited by another bee and likely contain little or no nectar. The bees move on. It should be mentioned that many kinds of bees leave mandibular chemical scent marks on flowers as they visit for pollen or nectar. These are also used by subsequent visitors to determine if the flower is worth their attention.

Bees also use the electrostatic charges acquired during flight to help collect pollen grains from flowers. This happens passively, solely as a result of the physics of bee flight and the negative charges on the dust-like pollen. The oppositely charged pollen grains from anthers can jump an air gap of about one millimeter and attach to the bodies of foraging bees. Many years ago, I made a high-speed sixteen-millimeter film documenting thistle pollen grains hopping off the thistle’s anthers and onto a charged rod. Pollen electrostatics also plays a large role in pollen harvesting during floral sonication (buzz pollination) of special flowers, which I’ll discuss in a later chapter.

Bees can be harmed by exposure to strong man-made electromagnetic fields (EMFs).⁴⁰ Honey bees exposed to 765-kilovolt electric fields showed abnormal behavior including queen loss and decreased winter survival. Sometimes beekeepers place their hives at apiary sites along roads directly beneath high-voltage transmission lines. Early studies indicate that these strong EMFs can have a negative effect on the bees’ overall health, navigation, and ability to make honey.

References: 

37. Flying bees become positively electrostatically charged, whereas plants and their flowers are grounded and therefore negatively charged. These charges can become detectable signals and markers for bees: Y. Vaknin et al., “The Role of Electrostatic Forces in Pollination,” in Pollen and Pollination, edited by Amots Dafni, Michael Hesse, and Ettore Pacini, 133–42 (Vienna: Springer-Verlag, 2000); E. H. Erick- son and S. L. Buchmann, “Electrostatics and Pollination,” in Handbook of Experimental Pollination Biology, edited by C. Eugene Jones and R. John Little, 173–84

(New York: Van Nostrand Reinhold, 1983).

38. Electrostatic charges on flowers can be visualized using electrostatically charged

colored powders and mathematically modeled: Dominic Clarke, Erica Morley, and Daniel Robert, “The Bee, the Flower, and the Electric Field: Electric Ecol- ogy and Aerial Electroreception,” Journal of Comparative Physiology A 203 (2017): 737–48, https://doi.org/10.1007/s00359-017-1176-6.

39. Bumblebees may leave electrostatic charges on flowers of about twenty-five millivolts that last for about one hundred seconds: Clarke, Morley, and Robert, “The Bee, the Flower, and the Electric Field.” Carpenter bees are known to leave man- dibular gland chemicals (scent marks) on flowers that repel other bees: Gordon W. Frankie and S. B. Vinson, “Scent Marking of Passion Flowers in Texas by Females of Xylocopa virginica texana (Hymenoptera: Anthophoridae),” Journal of the Kansas Entomological Society 50, no. 4 (1977): 613–25, http://www.jstor.org /stable/25082991.

40. Honey bees’ cognitive and motor abilities can be harmed by electromagnetic fields (EMFs) when the bees are placed by beekeepers under high-voltage lines: S. Shepherd et al., “Extremely Low Frequency Electromagnetic Fields Impair the Cognitive and Motor Abilities of Honey Bees,” Scientific Reports 8, art. no. 7932 (2018), https://doi.org/10.1038/s41598-018-26185-y.

From What a Bee Knows: Exploring the Thoughts, Memories, and Personalities of Bees by Stephen Buchmann. Copyright © 2023 Stephen L. Buchmann. Reproduced by permission of Island Press, Washington, D.C.