No spectacle of the tropical world is more exciting and mystifying than that of a colony of army ants on the march. In his book, Ants, Their Structure, Development and Behavior, Wheeler expressed its poetry in the following way: "The driver and legionary ants are the Huns and Tartars of the insect world. Their vast armies of blind but exquisitely coöperating and highly polymorphic workers filled with an insatiable carnivorous appetite and a longing for perennial migrations, accompanied by a motley host of weird myrmecophilous camp-followers and concealing the nuptials of their strange, fertile castes, and the rearing of their young, in the inaccessible penetralia of the soil--all suggest to the observer who first comes upon these insects in some tropical thicket, the existence of a subtle, relentless and uncanny agency, directing and permeating all their activities." (Holldobler and Wilson 1990).
Read an account of the biology of one of the best known army ant species Eciton burchelli.