A red wood ant Formica aquilonia (Hymenoptera: Formicidae) foraging for any insects it can capture, or any dead ones it can find. The forest floor under the canopy of a Norway spruce forest is dense with sphagnum mosses and lichens, making is laborious for ants to walk and drag dead insects back to the nest, this is probably the selection force that has enabled evolution of trail making and use by this species. Each nest of spruce needles (which may be a meter in height) typically has from 3 to 6 trails radiating out from the nest in various directions, often to a group of trees with Cinara aphids where the ants collect honeydew.

Images © 1996 by John A. Byers, Chemical Ecology.