This is weird ...
We were visiting with a neighbour this afternoon in his back garden, when I saw, on a toolbox, an ant. Nothing unusual about that; there were ants all over his place. But this one was behaving oddly, running around and around in a circle a couple of inches in diameter, always clockwise. I took a few photos, blurry ones because it was running fast.
We came home and I made tea. While we were drinking it, Laurie suggested that I could videotape the ant. Good idea: I finished my tea and walked back to the neighbour's place. (All that rigamarole to define the time span; 15 minutes to half an hour.)
The ant was not on the toolbox any more, but my neighbour thought it had gone down the crack. I moved the toolbox a few inches, and sure enough, there it was, going around in circles.
Here's the video (27 seconds).
Note how the ant responds to the fuschia petal when it blows into its pathway; it deals with the obstacle, then returns to the circling behaviour.
I checked out some of the other ants in the vicinity; they were all behaving normally.
What is going on? Some sort of parasite in its brain? Poisoning?