Pinpointing food sources: Olfactory and anemotactic orientation in desert ants, Cataglyphis fortis

Desert ants, Cataglyphis fortis, search for a repeatedly visited food sourc e by employing a combined olfactory and anemotactic orientation strategy ti n addition to their visually based path-intel:ration scheme). This behaviou r was investigated by video-trackimg consecutive foraging trips of individu ally marked ants under a variety of experimental conditions, including mani pulations of the olfactory and wind-detecting systems of the ants, If the w ind blows from a constant direction, ants familiar with the feeding site fo llow outbound paths that lead them into an area 0.5-2.5 m downwind of the f eeding station. Here, the ants apparently pick up odour plumes emanating fr om the food source and follow these by steering an upwind course until they reach the feeder. If the food is removed, foragers usually concentrate the ir search movements within the area downwind of the feeding site. Only when the wind happens to subside or when tail-wind conditions prevail do the an ts steer direct courses towards the food. Elimination of olfactory input by clipping the antennal flagella, or of win d perception by immobilising the bases of the antennae, altered the foragin g behaviour of the ants in ways that supported these interpretations. Ants with clipped flagella were never observed to collect food items.