The Myrmicine ants studied by Cornell researchers sometimes recruited seven or eight helpers. But army ants, generally regarded as being more advanced in an evolutionary sense, can summon thousands of compatriots with a single chemical signal. And more primitive ants, lacking a recruitment pheromone, leave no detectable trail. Pheromone receptors and the biological signaling apparatus that go with them are as sensitive as the finest analytical-chemistry instruments. Cornell researchers test this super-sensing ability by measuring the electrical current passing through an ant's antenna as different chemicals, separated from a complex mixture by a gas chromatograph, are presented to the receptor at the tip of the antenna.
Ants can detect just a few parts of their pheromone in a billion parts of air.
No wonder their batteries never seem to run down.