High rates of army ant raids in the Neotropics and implications for ant colony and community structure

Army ants form nomadic insect colonies whose chief food is other social insects. Here we compare the rate of army ant raids with the average density of their potential prey from 28 New World subtropical and tropical localities. We estimate that army ant raids occur at the rate of 1.22 m per day in tropical forests. Army ant raid rates increased with primary productivity, and with the density of potential prey (litter-nesting ant colonies), across sites. Our estimates of raid rates for army ant guilds are much higher than previously published estimates based solely on surface-raiding Eciton. Life-history theory predicts that high rates of predation on insect societies will select for both smaller average colony sizes and indeterminate colony growth, and these traits have been documented for tropical ant litter-nesting ants. Our results suggest that army ant predation can affect both patterns.