Body Painting Provides Remarkable Protection Against Horseflies
An ancient cultural tradition has a useful secondary effect.
Anyone who spends their summer outdoors knows bugs can ruin a good party. Fortunately, indigenous groups in Africa, Australia, Papua New Guinea, and North America have long benefited from a fashionable solution that scientists are only now understanding: body paint. According to a series of experiments in the journal Royal Society Open Science, stripes of paint across the body confuse some bugs because of how they diffuse the light.
For the study, a team of researchers from Hungary and Sweden set a bunch of horseflies loose on three differently colored mannequins in order to spare humans from the bites. One mannequin was light beige, one was dark brown, and one was dark brown painted with white stripes, but they were all coated with a thin layer of sticky glue to trap the hungry bugs. Placing them in a meadow for several weeks, both standing and lying down, and counting up the horseflies all the while, the team found that the striped mannequin attracted very few flies relative to the other two.
The beige mannequin was twice as attractive to horseflies as the striped mannequin, and the dark brown mannequin was 10 times as attractive as the striped one, supporting the team’s hypothesis that horseflies rely on their vision to seek out hosts — and that the Aboriginal Australians’ traditional method of artistic and religious expression also serves as an insect repellant.
Since horseflies are attracted to polarized light, white stripes on a dark mannequin disrupted the way that the insects saw the mannequins.
“This feature of bodypaintings is very useful, because on the one hand, host-seeking female horseflies can intolerably annoy people, and on the other hand, due to their blood-sucking habits, they are vectors of the pathogens of several diseases and/or parasites (e.g. tularemia, anaplasmosis, hog cholera, equine infectious anaemia, filariasis, anthrax, Lyme disease) and thus are dangerous or even lethal to humans,” write the study’s authors, led by Gábor Horváth, Ph.D., a professor of environmental optics at Eötvös University in Hungary.
As a side note, Horváth has also been a part of two different teams that won the notorious Ig Nobel Prize (“For achievements that first make people LAUGH then make them THINK”), once for a 2007 paper on how dragonflies are attracted to black gravestones, and once for a 2010 paper that showed horseflies aren’t attracted to white horses. A video describing the second paper can be found above.
Both of these sets of findings build naturally to what Horváth’s team confirmed in this latest paper. Due to the way that horseflies see polarized light, dark skin is more attractive than light skin. But when the polarized light reflected from the dark mannequins is broken up with white stripes, it becomes the least attractive of them all.
Light-colored bodypaint, while not necessarily used to protect against insect bites, turns out to be highly effective at deterring horseflies.
This research provides scientific evidence that this traditional practice is remarkably effective at making the wearer invisible to a nuisance insect. However, the team makes it a point to note that the primary use of body paint in the societies that use them is “social and cultural.”
“Bodypainting is normally a temporary part of social activities,” they add. “If bodypainting was only intended to repel horseflies, people would be likely to wear the bodypaint permanently. Thus, we find it plausible that deterring horseflies is simply an advantageous byproduct of bodypainting.”
