Relations between nests of Messor wasmanni in Greece

Foraging behaviour of Messor wasmanni, a seed collecting ant, foraging along trails up to 15m long in open flat ground in Greece, is described. These ants foraged in daytime on about one day in three, the nest entrance being otherwise closed with discarded remains of the plant material. They started approximately at dawn and material. They started approximately at dawn and continued until the ground surface temperature reached 40–43°C. Of the order of 20–30,000 individual foraging expeditions were made from the nest per day involving about 5,000 individual ants. They dispersed from the end of the trail and searched individually in limited areas of a few square feet (say half m²). Nests at a density of about 70 to the hectare were spaced in a pattern which was not random. Trails go out radially from each nest, usually a single trail in any day. Foraging areas for different nests overlapped but the chance of trails intersecting was low. An intersection was seen only once in approximately 500 trails from about a dozen nests examined in detail. The two trails met at right angles and the shorter one broke up at the junction, the ants from it going on across the other trail in the same general direction but more dispersed than before. All nests tended to forage after rain but the net synchronizing effect of this tendency was small, the nests in general foraging independently of one another in time. Calculation of the probability of trail intersection, allowing for the chance of adjacent nests having trails on the same day, and assuming a random trail direction together with the observed distribution of trail length gave a low value (7) for the expected number of intersections. No evidence of aggressive behaviour between different nests was found. Individuals, marked with paint and transferred artificially to a new nest, survived and foraged among those of their new nest. On three ocasions small subsidiary nests were found from which ants went to and fro along a trail to the main nest and on one occasion eggs and larval stages were transferred. On many occasions groups of ants dug small holes in the ground adjacent to a trail, which are most easily explained as incipient subsidiary nests.