Pascal Costanza (the OP) is a smart guy. He's behind the ContextL and AspectL frameworks, and he just published an interesting paper on implementing hygienic macros within an unhygienic macro system [1]. But in this instance, it seems he clearly missed the point of the Ants exercise.
Had he watched the Clojure concurrency video in which Rich extensively discusses the ant colony simulation and its purpose, he might not have made that mistake:
http://blip.tv/file/812787