Patterns of Foraging of the Forest Ant Formica neogagates Emery (Hymenoptera: Formicidae) on Tree Branches

Numbers of ants moving on trunks of oak trees and successive visits of workers of the forest ant Formica neogagates Emery to leaves of black birch trees were recorded in the forest. Ants were found to search systematically because they tended to move in the same direction on a twig before and after visiting a leaf. However, many leaves were skipped, and the probability of visiting an encountered leaf was about 0.5. Data were used to develop a computer model of ant foraging on leaves and twigs of trees. It was found that reasonable model outputs of numbers of leaves skipped between visits and the number of new leaves visited, as the total number of visits increased, could be obtained only if ants were assumed to partially avoid leaves that they had previously visited. Model results implied that 100 ants in a tree foraging for about 3 h should be able to visit about one quarter of the leaves in a tree.