Body-painting protects against bloodsucking insects | Hacker News Reader

Body-painting protects against bloodsucking insects

sciencedaily.com

146 pointscurtis56 comments

> For the experiments, which were conducted in Hungary, the researchers painted three plastic models of humans: one dark, one dark with pale stripes and one beige.

Did they also test with actual humans? A living body might be more attractive to the insects, maybe reducing any advantage from the stripes.

No, it doesn't appear so.

So much this. They definitely sense CO2 and thermal/IR.

I think the issue is that they wanted to first identify and test the idea first. If you add in humans, you have to find volunteers and then waivers because no one is really willing to hang around in the nude and get bit by horseflies for a day.

As well for humans, you will have to consider demographical data and other data like gender, height, weight, body fat, in general how healthy the human is etc. which lead to even more questions.

Using just the models can mitigate these concerns

Why do you have to be nude, or hang around? Just go about your day normally and count bites at the end.

Seems like people covered head to toe with body paint would have a different “normal day” then the control group.

I remember reading about some experiment involving mosquitoes and body odor, IIRC they were done behind a mosquito net. I seem to remember the takeaway was: wash your feet well.

Last year, the YouTube channel Veritasium did a video about it: https://youtube.com/watch?v=38gVZgE39K8

> As well for humans, you will have to consider demographical data and other data like gender, height, weight, body fat, in general how healthy the human is etc. which lead to even more questions.

You could control that out to an extent by painting half of each volunteer, and then comparing the number of bites on each side.

Of course you'd want to randomise which side was painted, in case the insects prefer to bite one rather than the other.

It’s unlikely the effect would work at all like that. Insects are certainly able to estimate the full figure, and with the hard break in stripes down the center the results would probably be tainted

> If you add in humans, you have to find volunteers and then waivers because no one is > really willing to hang around in the nude and get bit by horseflies for a day.

You'd be surprised. Naturist love hanging around nude in places where insect bites are a serious possibility.

Not because of the insect bites of course. They just literally come with the territory. But if there was ever a demographic where this research would be very relevant, it's probably naturists.

Yes, a living body will be more attractive to the insects, which is exactly why they will have used plastic ones. If you used real people, you don't know if the attractiveness changes is due to the body paint or differences in the human to the control sample.

It appears that they covered it with glue, so that they could count the insects at the end of the day. While this does definitely raise some questions, it also made the initial test probably quick and easy; no human test subjects needing to sign a waiver that they were willing to hang out covered in glue all day. Kind of like testing things on lab rats first.

Definitely would need to be tested in some other way, though. Lots of things that work on lab rats don't work on humans.

Wasps (and to a lesser extent flies) also remember how they came into a room, and can get back out quickly: imitate a bat with a hand (flickering fingers back and forth) and they usually zoom right back outside the way they came in. In evolutionary terms, they've entered a cave, and caves have bats: so they have an exit strategy ready to hand.

Except if the room has a tilted open window. It comes in through the window, but never discovers how to escape anymore from it since it keeps trying to fly towards the outside light through the glass rather than going up a bit and flying through the actual open gap.

At least that's my experience, and of course that's quite annoying behavior when you'd rather have it go outside the house!

But maybe I should try this "bat signal" next time :)

careful, the bat signal should only be used when Gotham is in danger!

You know, if Batman were keeping tsetse flies and mosquitoes at bay, he would save a lot more lives, really.

Another instance of Wittgenstein's bottle, or a typical aboriginal fish trap.

> imitate a bat with a hand (flickering fingers back and forth)

Could anyone describe this in more detail, or link a video? My web- searching has failed ne.

I, too, wish to know how to make wasps leave the premises with some hand motions

You make it sound like a magic Repel Insects spell.

Sufficiently advanced technology.

This comment applies so profoundly to the original article, doesn't it - the body painting was too advanced for European understanding, so it was taken to be magic in the useless, mere superstition sense of that term. Not quite what Mr. A. C. Clarke meant to point to, but it fills out the meaning behind his point and buttresses it, in my mind.

Wiggle your fingers up and down, as independently (of each other's motion) as possible.

It certainly seems like the heat, sweat, and scent of a living human might affect the results.

But, what do I know? Motionless plastic figures might be treated exactly the same as well.

Exactly. And what might also influence the results is the "scent" of solvents and other chemicals, that might differ from color to color.

There is a swimming spot I love that has a large population of horse flies. They will not land on stripes or go into the shade. They will land on flower prints (I found that one out the painful way)

Could this be a new hint to the reason for a zebra's stripes?

Yes, apparently: https://news.nationalgeographic.com/news/2012/120209-zebra-s...

> or go into the shade.

Maybe they don't want to get bit by mosquitoes? I'm half joking of course, but when I'm out kayaking, it seems that, in my observation, most insects, including mosquitoes, prefer the shade, so I tend to stay out of it.

What amazes me about this is that the body-painting was considered by Europeans to be evidence of the 'primitive nature of lesser cultures', yet it turns out it was actually kind of advanced technology.

I hope to witness more instances where the old imperial, intolerant ways of looking at the cultures we've degraded over the last few centuries get turned upside down. There are so many things we could have learned about the world from the 60,000+ year old culture of the original inhabitants of Australia, which might've pushed us further.

I put this 'stripes as insect repellant' in the same list as 'they had a Hippocratic oath before us', and 'they understood antibiotics and antiseptics while we were still arguing over miasma theory and bloodletting'.

Turns out, their technology was more advanced than our hubris allowed us to admit.

I hadn't heard that about antibiotics. Got a link?

Not 100% sure if this is what GP is referring to, but: https://www.wnycstudios.org/story/best-medicine (podcast episode)

There was this story in Science last year about a 90% success rate in cranial surgery by Pre-Columbian Inca physicians. Their sample sizes are low but an observed scaling up of success rates over a 400 year period speaks to institutional mastery beyond what western medicine was able to accomplish until after the discovery of antibiotics.

http://www.sciencemag.org/news/2018/06/south-america-s-inca-...

Look up the use of emu bush by the Northern Territory tribes, for example ...

> I hope to witness more instances where the old imperial, intolerant ways of looking at the cultures we've degraded over the last few centuries get turned upside down.

Another example is the "utter idiocy" of Berbers wearing black clothing in the desert heat. (https://www.nature.com/articles/283373a0). Actually it's neutral (a far as temperature goes) but has other advantages including making you harder to see and, of course, social/decorative/signalling value.

This was actually the first scientific paper I deliberately went to find and read after reading about it in some other journal. I was 16. Luckily it was something approachable and so encouraged me to spend more time doing it.

And now, with make-ups meant to fool the AIs, the story kind of repeats...

> A brown plastic model of a human attracted ten times as many horseflies as a dark model painted with white stripes. The researchers also found that a beige-coloured plastic figure used as a control model attracted twice as many bloodsuckers as the striped model.

This seems to confirm that light clothes are better than dark ones at protecting against bites. 5x more effective. The stripes add another 2x but wearing mostly black clothes in hot areas has some disadvantages. Maybe I'll stick with my beige cloths.

> wearing mostly black clothes in hot areas has some disadvantages

What are the disadvantages? An advantage is that black clothes are better at radiating your body heat and protecting against sun burn - that's why people often wear black in hot countries.

https://www.nature.com/articles/283373a0

If standing out in the sun, it would be more beneficial to wear white, while black tight clothes in the shade?

I've seen many bedhouin men wearing white.

Funny, I remember some similar tests by scuba divers in the 90s. They dressed in black and white striped suits thinking they would look like sea snakes and everything would stay away. Didn't go so well. Lots of stuff was very interested in them. Don't do this underwater.

I couldn't find any references to what you mentioned ( very quick search ), but this turned up about using stripes to camouflage surfers against sharks.

https://www.theatlantic.com/technology/archive/2015/07/shark...

Same stripes, different concept. That is to prevent big sharks from thinking you are a seal. Deep colder water. The trials i read about went wrong because some smaller sharks (reef sharks) might in fact eat sea snakes.

I remember reading about this a long time ago. At a glance, the earliest research around here goes to 2012. Related to Zebras and Horse Flies.

Summary: http://jeb.biologists.org/content/215/5/iii

research: http://jeb.biologists.org/content/215/5/736?iss=5

Is this why zebras have stripes?

Against colour blind predators, zebra stripes are pretty good camouflage. I suspect it is more to do with avoiding lions than mosquitoes.

we tend to underestimate the evolutionary impact of parasites and disease. Mosquitos are a major vector; could very well be the mosquitos

I can't imagine it would take long for mosquitoes to evolve to specifically gravitate towards stripes...

Well it's hard to know what fitness terrain lay between the present phenotype and that one, so it's necessarily obvious bthat such an adaptation would occur. Nor is it obvious that stripe attraction is more adaptive. Could be hidden costs I'm not cognizant of. In any case, we were speaking of the zevras adaptation, not the mosquito's. If true that mosquitos are not attracted to striped things, it doesn't matter why zebras have stripes. What matters is the cost to mosquitoes presently incurred by missing out on all that zebra. Indeed, one wonders why mosquitos haven't adapted to the zebras stripes already...

It may be hard for their tiny brains to distinguish stripes from other things that are not animals.

Yes.

From The function of zebra stripes[1]:

> Despite over a century of interest, the function of zebra stripes has never been examined systematically. Here we match variation in striping of equid species and subspecies to geographic range overlap of environmental variables in multifactor models controlling for phylogeny to simultaneously test the five major explanations for this infamous colouration. For subspecies, there are significant associations between our proxy for tabanid biting fly annoyance and most striping measures (facial and neck stripe number, flank and rump striping, leg stripe intensity and shadow striping), and between belly stripe number and tsetse fly distribution, several of which are replicated at the species level. Conversely, there is no consistent support for camouflage, predator avoidance, heat management or social interaction hypotheses. Susceptibility to ectoparasite attack is discussed in relation to short coat hair, disease transmission and blood loss.

[1] https://www.nature.com/articles/ncomms4535

I remember my mother telling me that black clothes attract mosquitoes.

So we can wear zebra t-shirts and have less bites, possibly?

I read somewhere about zebra stripes long ago.

I am certain there are a set of FAANG and political jokes lurking in this headline. I hope this meta comment will slake any desire to post them on HN.

The idea of a subreddit just for posting things that you want to post but shouldn't would have some merit. Sort of a safety valve of sorts.

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