More Entomology (Ants and Chalk)

Why don’t ants like chalk (calcium carbonate)? If you find an ant on a sidewalk, and draw a circle around it (the ant) with a piece of chalk, the ant will not cross the line (at least not immediately).

O.K… let’s get this out of the way… Yes, I do have too much time on my hands.

How about we draw a circle around Steve-o?

      • The book I read this in said that ants don’t seem to like crossing white lines and offered the example of chalk - it just happens to be a common way of making a white line somewhere ants are likely to be found. I haven’t tried it with anything else. - MC

Yeah… but… if you draw a circle around me… how am I supposed to go to work? Hmmm… perhaps I’m starting to like that idea.

As for ants not wanting to cross any white line, I wonder… Surely they cannot actually see that the line is white (or can they). Perhaps it is that the white line’s reflection of light makes the line appear bright, and evolution has taught ants not to walk into bright things (such as fire, or concentrated light from magnifying glasses (pop!)). I have quite a few ants around my house, so I think I will do some experimenting.

Ants find their way by marking their paths with scent trails. Possibly, when you draw a line around the ant, you’re disrupting that trail, and the ant has to look harder to find it.

Lissa -

That had occurred to me during my original experimenting, so I procured an ant trap (piece of paper for it to crawl on), and captured the beast. I then transported it to a remote location (further down the sidewalk), and released the creature into a previously drawn circle of chalk. After about 2 minutes, the ant did cross the line, but up 'till it crossed the line, it turned around each time it came to the line. I thought that what probably happened is that it was marking its trail inside the circle, and finally “realized” (after crossing his own trail several times) that it was trapped. At this point it had no “choice” but to cross the line.

By the way, when that dang ant crossed the line, I had to put my foot down. Bwahhahaha

Isn’t this how Dahmer got started?

My theory is that the chalk particles are abrasive. I know that you can use diatomaceous earth as a pesticide, and the way it works is that its tiny particle invade the bugs’ bodies and abrade them to death. Chalk seems very similar to diatomaceous earth in that it is made up of relatively large particles which could scratch an ant up pretty bad if it got in the wrong place – kinda like sand in the old swimsuit, if you follow my meaning.

President of the Vernon Dent fan club.

Nah, Nick. I, too, used to think humans could not get out of a chalk outline. Then I found out that the chalk lines were drawn around those bodies after they were dead. The police do it. Dahmer must have killed them some other way.

The overwhelming majority of people have more than the average (mean) number of legs. – E. Grebenik

Back when I worked at a student store, we always used talcom powder to stop ants in places where we didn’t want to use poison. Our working theory was that the powder was like small, loose rocks to the ants, and they had trouble crossing without stumbling. Now that I think of it, that sounds like a pretty stupid theory.

It’s probably a combination of things. Ants can see the lines, but I’d bet they would behave the same even in pitch darkness. Also, there are any number of substances that would cause the same basic response - that is, hesitancy to continue moving in that direction. That sort of hesitation does not necessarily mean that they are repelled by chalk, though the idea that chalk works like diatomaceous earth is probably a pretty good theory, since that is pretty much what chalk is, except just the marine equivalent (full of shells of foraminifera, radiolarians, etc.). Gets into the breathing passages and wreaks havoc.

I think Doug Yanega is on the right track when he suggests that chalk gets into the breathing passages and wreaks havoc.

As I understand it, rather than a thick bark for protection, aspen trees instead developed a coating of fine white powder. The powder protects the tree from invading bugs by clogging the little critters’ air passages, which in many species are located on their undersides. Rather than a tasty aspen treat, the insects get death by asphyxiation.

Perhaps chalk does the same thing.

~ Complacency is far more dangerous than outrage ~