h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In ancient times, Indra had gotten a little carried away with a building spree, with the consequence that at one point Krishna marched a column of ants through Indras' palace in ranks and files.

When Indra protested, Krishna responded that these were "... all the other Indras.".

Leaving aside interpretative material like the classical Greek appellation for soldiers, 'Myrmidons', or ants, possibly because the straggling column of an army on the march viewed from a high place reminded people of ants on the march, lets say one is talking about real ants.

Its simplicity itself to get common ants to march in a column, one merely needs to paint the course the ants are to march with a thin solution of formic acid, just barely enough one can smell it, run the trail back to an active ant hill, and the ants will set out on a march since they use formic acid to mark their scent trails, making it easy in turn to set the ants up so that they march in discrete files. At that point I mentioned this and remarked that I couldn't quite see how someone would be able to get the ants to march in 'ranks' as well as files.

Then someone pointed out that some tropical ants use a system of two scent markers rather than just one like most temperate ants.