Nomadism either develops concurrently with group raiding behavior or is added shortly afterward. Emigrations to new nest sites allow a colony to shift to new trophophoric fields with more abundant prey. This combination exemplifies army ant behavior. As group perdition becomes more efficient, large colony size is possible. Diet may expand to include other smaller and non-social anthropods, some small vertebrates, and vegetable matter.
Colonies become quite large.
Early Tertiary origin for the Dorylinae. Schneirla postulated a similar origin and explanation for the distribution of the ants. The end of the Cretaceous already separated the three tropical areas in which the true army ants are the army ants as figure 2 shows have a worldwide distribution, with representatives in each hemisphere roughly between 45 degrees north and 45 degrees south. They are found in most tropical and subtropical parts of the world with some notable exceptions. In the New World Chile, the volcanic islands of the Caribbean, mountain heights, and certain extensive desert and swampy areas.