The vital question: how do ants measure distance, for example from a food source back to their colonies?
Well, Messrs Wittlinger, Wolf and Wehner hypothesized that they do so by counting paces. To test this, they "altered the legs on a group of ants." Some were placed on pig-bristle stilts, others had their legs amputated (ouch).
The fellows on stilts went too far. The amputees didn't go far enough. QED, or as near as you can get with ants. (One report here).
You feel for those amputees, but nevertheless, isn't that just delightful? Gotta love science.
Postscript: A reader points to this fine explanation of ant movements, including orientation and distance.
I also thought I'd point you once more to this prize-winning photograph, though for the time being, the ants involved don't appear to be in need of distance measuring mechanisms.