Plant design and non-random foraging by ants on Croton bonplandianum Baill. (Euphorbiaceae)

Abstract

Croton bonplandianum bears female flowers in inflorescences which are arranged in a regular pattern. Foraging individuals of the ant Camponotus sericius feed on the nectar in the nectary glands of female flowers. The pattern of movement of ants while foraging between these regularly placed inflorescences was highly systematic and distinctly exploratory. The ants tended to visit new inflorescences at each move and avoided revisiting inflorescences. They followed this foraging pattern by adopting circular movements either to the left or to the right and avoiding other complex but equally effective moves. This was probably due to memory constraints. The ants predicted the resource quality of the subset of a patch by sampling a part of it. The inflorescences within a cluster were similar in quality. Using this relation ants could make decisions about continuing to forage in a cluster after sampling any one inflorescence. If the first inflorescence visited was of poor quality they abandoned the cluster. This ensured efficient foraging with minimal expenditure of time and energy.