Category Archives: Education

Shaving your legs to deter ticks

Colin Purrington Photography: Green steps &emdash; girl-with-shaved-legsPeople shave their legs for a variety of reasons: to look younger (artificial neoteny), to look less like men, to show off tattoos, to show off muscle definition, to improve athletic performance (less drag, plus fools brain into thinking you’re going fast), to facilitate post-accident wound cleaning (cyclists), and because shaved legs induces a pleasurable sensory overload (at least to some). But can shaving also protect you from ticks? I became curious this week after watching a tick crawl up my leg (photograph below). I was really surprised to discover that no experiments on this topic have been done, but did succeed in finding three relevant snippets on the internet (two from mountain bikers, one from cross country runner):

“One thing that helps is shaving your legs. Not a foolproof way but I would say it reduces them critters by 80%, maybe more. I noticed that when my wife and I were out and she had none, I had around 14 that day.” source

“As an experiment I shaved my legs before riding point to point at lbl with KRS and a few others. It was tick season. After 40+ miles of riding I had 1 tick on my sock. Along the way KRS pulled OVER 15 ticks. We rode the same route at the same pace. I’ve kept the hair off ever since.”  source

“I’d say its mostly impractical. Although, I know many trail runners (including myself sometimes in the summer) do it to prevent ticks from attaching.” source

But, hey, maybe the anecdotes are just that, and hairy legs actually deter ticks in some way. 

Colin Purrington Photography: Spiders and ticks &emdash; American dog tick (Dermacentor variabilis)

But it makes sense that shaving would deter ticks. The first is obvious: ticks can grip hair, so if you are hairless (and are wearing shorts, skirt, or kilt), they can’t climb as fast (they are headed for your groin, by the way). The second is that you if you have hairless legs you can most likely better feel them crawling up your legs. I.e., all eight of their legs are touching your skin’s sensory array (or all six of their legs if they are larvae). The third is that when you remove all your leg hair you are removing a lot of sensory distractions caused by wind (experiment on swimmers), and thus you can zero in on things crawling on you. Indeed, all of these mechanisms might touch on why we evolved to be relatively hairless in the first place

So about the experiments that need to be done …

An easy way to assess would be to count numbers of ticks on a group of people out for a walk, some of whom shave. But at least in the United States, that would break down to men versus women, and males smell worse than women and thus might attract more ticks, regardless of hirsuteness. And men are usually larger, so there’s the surface area thing that goes against us, too. So it would be far better to recruit a group of hairy-legged women and ask them to shave just one leg, then march around a field known to have ticks. Participants would tie white bandanas around their upper thighs to arrest the ticks before they got too intimate, then count tick numbers. But finding enough women who don’t shave might make the protocol hard to follow (again, at least in the United States). So perhaps using a group of guys would be more feasible. An ideal group might be a men’s college swim team right before the season begins. Just ask the coach to donate their legs for science. Would be an easy publication for a day’s work, and the experiment would be crazy photogenic. Plus great team-building exercise. Would get the college on the evening news I’m sure. 

A simpler design might be to just have a motivated group of people (perhaps students in a field ecology course?) conduct tick races on shaved, unshaved legs. You just need to start them on the ankles and have participants hold still while the ticks make their ascents. That would be equally photogenic and fun, I think. And to get at the perception part, you could have blindfolded participants that would be asked to identify location of ticks crawling up legs (with controls being placement of non-ticks on ankles, perhaps).

The proposed experiments might seem horrific, but just the for record, I once swam around the edges of a small pond just to see how many leeches would attach to me. I recall that my father challenged me, and that we were going to see who could win. I don’t remember who ended up with more. (Yes, that was a nerd x testosterone interaction effect.)

If somebody does go ahead and conducts this experiment — and if the effect is huge (my guess) — the next step would be to alert the folks at the CDC so they could add a shaving recommendation to their tick page. The reaction to that would be entertaining.

Posted in Biology, Education, Gardening, Photography, Science | Tagged , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

Conference poster full of tips for creating conference posters

In case you need a quick guide to making a conference poster, here are two versions of my poster of poster tips. They have content overlap, so just choose the layout that pleases you. More details below the images.

Poster example (Colin Purrington's)Advice on designing scientific posters

Both posters are descendants of a document I created circa 1997 for my evolution students at Swarthmore College. The bottom one is available as a PDF if you want to print an actual poster of it — which I highly recommend if you are assigning a poster project for your class (students don’t like reading the website, below).

My full tips are at Designing conference posters. I created the website for my students, too, but eventually made it public in case it might help make the world’s poster sessions more enjoyable and their posters easier to understand. Please share with your friends.

Posted in Education, Science | Tagged , , , , , , , , , , , , , , , | 4 Comments

Etymology of garter snake

Colin Purrington Photography: Reptiles &emdash; Eastern garter snake (Thamnophis sirtalis sirtalis)Even though “garter snake” has been the common name for Thamnophis sirtalis for over 200 years, I discovered this week that people who know a lot about garter snakes don’t agree on why. There are two theories: (1) the snakes were named after stocking garters and (2) sirtalis is the Latin word for stocking garters and thus the common name was derived from the Latin binomial. I know, not a burning question for most, but I was curious given that snake fans seem to choose one or the other without further mentioning why. So I looked into it. 

Garter holding up a woman's stocking (from The Practical Costumer)
Photograph of an embroidered garter. Image from the The Pragmatic Costumer (click image to read her article).

(1) Most articles, books, and websites explaining the common name suggest it’s because the snakes resemble garters, pieces of fabric that were fastened right below one’s knee (the garet, in Celtic) to keep stockings from falling down (that used to be a huge problem). The resemblance is lost on most people today, especially guys who don’t know their lingerie history, because garters are now frilly and made of silk or satin and thus not at all snake-like. But back in early Europe they often had lines and patterns that could easily remind somebody of the stripes and scales of a snake. And everyone wore them: women, men, even kings, so they were ubiquitous, visible, and probably conversation starters. So it’s not surprising that somebody eventually referred to a particular type of snake as a “garter” snake. 

In etymology it’s important to establish when a particular word first appears, so I consulted the Online Etymology Dictionary and learned that garter snake first shows up in 1775, in the United States. The Online Etymology Dictionary says the name is related to stocking garter but doesn’t provide proof of this or any links. Curious, I found that “garter snake” shows up even earlier, in 1773, in a description of specimens in somebody’s collection in Lichfield, England. Again, there is no explanation of why the common name was garter. I’m sure the first usage of “garter snake” goes back even further, too, if you had access to a good database of letters and newspaper articles from the time. I don’t.

(2) A potentially related hypothesis for the common name is that sirtalis means “like a garter”. This is exactly the claim thousands scientists and naturalists make. If true, then the common name might have been launched when Linnaeus published his classification in 1758. Alternatively, maybe it just confirms that he knew of the common name and simply applied the Latin cognate for the species. But I was suspicious of this claim because when Latin was a living language there weren’t stockings or the need for garters. Sure enough, when you look up sirtalis in a Latin dictionary, it’s not there. Like many of words Linnaeus used in his binomials, he made it up by combining Latin and Greek roots, leaving us to guess at what the new word might mean. Kraig Adler theorizes that the word might be a combination of siro (Greek for cord, rope, or string) and talis (Latin for such, the like), and thus might mean “ropelike”. So when people claim that sirtalis means “like a garter”, they are incorrect. The first appearance of the “like a garter” claim seems to in 1976, in Robert Parker Hodge’s Amphibians and reptiles in Alaska, the Yukon, and Northwest Territories. I don’t own the book so I’m not sure if he cites somebody, in turn.

Although sirtalis does not mean “like a garter”, I guess it’s possible that Linnaeus had garters in mind when he concocted a rope-like species name for the snake. He probably wore garters, and perhaps called these snakes “garter snakes” before he officially named them. The question, then, is whether the common name predates his scientific name. In looking into this I discovered a second common name that I think was borrowed from German or Dutch: kouse band. The French use serpent jarretier (jarretier means garter), and Swedes use strumpebandssnok. Anyway, it seems that everyone in 1790s Europe, regardless of language, called them snakes-that-look-like-garters. Would be nice to know which language first started to call them by the respective name, but to do that I think I’d need something other than Google’s English-based book search. Note that the 1773 date I mentioned above was found with Google, and thus is probably simply related to my usage of the English-language version. There are likely other databases out there without such language problems.

A deservedly rare explanation for how the garter snake got its name is that it is a misspelling of guarder snake, garden snake, gardener snake, or garten snake. Some of these variants are quite common on the internet, and I think most people can blame their parents. 

Posted in Biology, Education, Photography | Tagged , , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

Small winter stonefly

I was out looking for the elusive snow fly yesterday but found this, instead: an eastern stonefly (Allocapnia recta), a member of the Capniidae (small winter stoneflies). At least that’s what I think it is. Larvae are active during the winter, and adults can fly and mate even when temperature is in the teens. Pretty incredible to see them flitting around on a cold day when other insects cannot even move. At Hildacy Farm in Media, PA. Probably emerged from the nearby Crum Creek. 

Colin Purrington Photography: Insects &emdash; Eastern stonefly (Allocapnia recta) Colin Purrington Photography: Insects &emdash; Eastern stonefly (Allocapnia recta)

Posted in Biology, Education, Photography, Science | Tagged , , , , , , , , , , , , , , , , , | Leave a comment

Trigger warning for creationist visitors to National Zoo

Here’s a photograph I took several years ago at the National Zoo’s “Think Tank” exhibit on primate cognition. Darwin Day is one week so I thought I’d share.

Colin Purrington Photography: Evolution graphics &emdash; Think Tank warning for creationists

The text is a little hard to read so here’s transcription:

“This exhibit is about animal thinking. It contains some things you may agree with, some you may disagree with, and others that may even trouble you. Come explore and see what you think.” 

The warning sign was crafted by Smithsonian staff to cater to snowflake creationists who complained about the “Changes over millions of years have resulted in today’s humans” panel that covered the age of the earth, human evolution, and how natural selection works. 

The “see what you think” part suggests to visitors that the facts presented within are up for debate and thus shouldn’t undermine somebody’s alternative views about human origins or the age of the earth. But, of course, the warning signage undermines the experience for all visitors. I.e., a curious but uninformed visit might assume that the exhibits are just wild guesses about what might have happened. A shameful use of tax dollars, in my opinion.

Posted in Biology, Education, Graphic design, Photography, Science | Tagged , , , , , , , , , , , , , , , , , , , , | 1 Comment