“Trail Communication and Directional Recruitment to Food in Red Wood Ants (Formica)”, 1987 (; similar):
Laboratory experiments confirm that protein-starved red wood ants of the Formica rufa [red wood] group and Formica truncorum Fabr. react to the presence of protein baits in the foraging area with alerting and orienting signals resulting in directional recruitment. Evidence is presented that the cause of directional recruitment in F. rufa group ants is a scent trail laid from the bait toward the nest, while “centripetal” recruitment, due to orienting signals provided by scouts returning to the bait from the nest, is of negligible importance.
An interesting complication was detected in F. truncorum, which showed adequate communication of direction to a food source in the light, but not in the dark. Alternative explanations for the latter phenomenon are discussed.
The laboratory results are related to field observations of red wood ant colonies, which indicate a rather limited use of directional recruitment, because of the stable distribution of resources.
It is pointed out, however, that temporary shortages of resources, especially in spring, may have favored evolution of mechanisms for directional recruitment.
“A red wood ant colony remembers its trail system leading to the same trees, year after year, although no single ant does. In the forests of Europe, they forage in high trees to feed on the excretions of aphids that in turn feed on the tree. Their nests are enormous mounds of pine needles situated in the same place for decades, occupied by many generations of colonies. Each ant tends to take the same trail day after day to the same tree. During the long winter, the ants huddle together under the snow.
The Finnish myrmecologist Rainer Rosengren showed that when the ants emerge in the spring, an older ant goes out with a young one along the older ant’s habitual trail. The older ant dies and the younger ant adopts that trail as its own, thus leading the colony to remember, or reproduce, the previous year’s trails.”]