Army ants have a decidedly tropical reputation. The term conjures spectacular images of swarms sweeping across remote Amazonian villages, devouring chickens, cows, and small children unlucky enough to find themselves in the path of the ants. Of course, the habits of real army ants are not nearly so sensational, but they are at least as interesting.
Few people are aware that more than a dozen army ant species are found in the United States. Most belong to the genus Neivamyrmex, a diverse group that extends from Argentina to as far north as Iowa. Their colonies are populous, comprising tens of thousands of individuals, and like all ants, theirs are composed largely of sterile female workers, a single reproductive queen, and on occasion winged males for dispersing the colony’s genes.
As Neivamyrmex is a true army ant, colonies do not make permanent nests. Instead, the ants rove across- and under- the landscape, making temporary bivouacs out of their own bodies but never lingering for more than a few weeks.
Their prey is other ants. Neivamyrmex is highly specialized for finding and exploiting nests of other ant species. Unlike some of their famous tropical cousins, they do not form diffuse swarms but instead organize their foragers into tight columns. This way they concentrate their forces into a single point, ideal for overwhelming the guards of their target nests.
The photo essay below documents some of the drama, and some of the biology, of the most northerly of the army ants.