Ordinary chalk can be used to keep ants at bay; drawing a line or circle around the protected area may prevent them from entering.[citation needed]
-http://en.wikipedia.org/wiki/Ant

What the hell is this? The Wicca school of insect control? Does an upside-down pentegram summon a giant demonic ant? Any counter-spells I should know?

(In all fairness, the extreme bitterness and lack of nutritional content of chalk may keep ants out, it just struck me as funny.)