Higher soil temperatures cause faster running and more efficient homing in the temperate thermophilous ant Formica cinerea (Hymenoptera: Formicidae)

Thermophilous ants, which live in many places at very different latitudes, can on occasion face similar thermal conditions. The temperature of the sand in a Euro-Siberian forest clearing can reach 61 degrees C, a temperature that is above the thermal maximum of most foraging ants. Therefore, we expect that temperature may have a similar effect on the foraging strategy of species living there, for example, Formica cinerea, as it has on the foraging strategy of typical thermal specialists. We experimentally tested in the field whether workers with higher mean speed are more efficient than slower individuals by comparing their path shapes as they return to the nest. More specifically, we asked whether workers' time taken to return to the nest and the straightness of their paths from the feeder to the nest are affected by workers' speed and surface temperature. As temperature increases, workers walk faster and take less time to return to the nest. The speed of workers influences the straightness of their path from the feeder to the nest - the workers with the higher mean speed take a less sinuous return path to the nest. We conclude that workers with higher mean speed are more efficient than slower individuals.