Wet Grapes
My ants often enjoy a grape. I slit the grape skin open, and they burrow into the juicy flesh for days, hollowing it out.
Or, I might offer them a slice of grape, as above.
I've noticed that as the grape dries out, the ants pay less attention to it. By re-hydrating the grape with a dash of water, it becomes much more appealing to the ants - they go crazy for it!
A video accompanies this photograph within my Video page, at the bottom right.