Foraging trails of the ant Formica neogagates Emery on leaves of trees and shrubs in the forest or on artificial leaves in a laboratory arena were recorded and digitized. About the same proportion of a leaf was explored by ants whatever the plant species or size of leaf. The portions and numbers of leaves revisited by ants were consistent with the hypothesis that ants do not recognize areas they have recently explored. Trail characteristics of ants foraging on artificial laboratory leaves were similar whether or not leaves had a drop of honey at their base, except that on leaves with honey, more trails occurred and large turning angles were more frequent. By continually watching ants as they climbed up and down tree trunks in the forest, I was able to deduce that up to 150 individuals of F. neogagates may be in a tree at any one time, and that some ants forage in trees for at least 4 h at a time. At this foraging intensity, a significant fraction of the leaves on a tree could be explored by these ants in a day.