Striped Bodypaintings Deter Blood-Sucking Flies: Study

Bodypainting is widespread in African, Australian and Papua New Guinean indigenous communities. Many bodypaintings use white or bright stripes on brown skin. A new study published in the journal Royal Society Open Science shows that these stripes protect skin from insect bites.

Reflection-polarization characteristics of the sunlit sticky white-striped brown human model. Image credit: Horvath et al, doi: 10.1098/rsos.181325.

Reflection-polarization characteristics of the sunlit sticky white-striped brown human model. Image credit: Horvath et al, doi: 10.1098/rsos.181325.

Members of different tribes living in Africa, Australia, Papua New Guinea and North America frequently paint their brown naked body surfaces with white or bright stripes. The patterns of these paintings are extremely diverse and are used as body decoration, for emotional expression or as marks to signify personal identity or group affiliation.

In areas where people using bodypaintings presently live, there are usually abundant horsefly populations, and because the main part of the body surface is usually exposed when wearing these paintings, they are vulnerable to attack by blood-sucking horseflies as well as other insect parasites, like tsetse flies and black flies.

Horseflies prefer to attack and suck the blood of dark-coated mammals. The darker the host animal, the more attractive it is to horseflies.

However, the attractiveness to horseflies decreases with increasing heterogeneity of the body pattern, such that host animals with thinner and more numerous stripes on their coats attract fewer horseflies than hosts with wider and fewer stripes. The most striking striped mammals are zebras, in which it has been shown that their striped body pattern reduces their attractiveness to horseflies.

“Body-painting began long before humans started to wear clothes,” said Lund University’s Professor Susanne Åkesson, co-author of the study.

“There are archaeological finds that include markings on the walls of caves where Neanderthals lived. They suggest that they had been body-painted with earth pigments such as ochre.”

Owing to the resemblance between zebra stripes and the bright stripes of traditional bodypainting, Professor Åkesson and colleagues hypothesized that bodypaintings have the advantageous effect and protect humans visually against the attack of blood-sucking insects.

For the experiments, the researchers painted three plastic models of humans: one dark, one dark with pale stripes and one beige.

They then covered the three models with a layer of insect glue.

The dark model attracted 10 times more horseflies than the striped model, and the beige model attracted twice as many as the striped one.

The team also examined whether the attraction of horseflies differed between models that were lying down or standing up.

The results show that only females were attracted to the standing models, whereas both males and females were drawn to the supine models.

“These results are in line with previous experiments in which we showed that males gravitate towards water in order to drink and land on surfaces that reflect horizontal, linear polarized light, such as signals from a water surface,” Professor Åkesson said.

“Females that bite and suck blood from host animals respond to the same signals as the males, but also to light signals from in the vertical plane, such as the standing models.”

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Gábor Horváth et al. 2019. Striped bodypainting protects against horseflies. Royal Society Open Science 6 (1); doi: 10.1098/rsos.181325

 

 

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