Foraging activity of the attine ant Acromyrmex octospinosus (Reich) (Hymenoptera: Formicidae) on resistant and susceptible yam varieties

Abstract

AbstractA quantitative analysis of the foraging behaviour of Acromyrmex octospinosus (Reich) from three nests on 27 yam varieties of nine species was undertaken in Guadeloupe using a video-microcomputer device. In ants with no previous experience of the variety, foraging inhibition appeared only after at least a whole day of contact with resistant yam leaves. There was a negative correlation between leaf saponin content of the yam species and foraging intensity; however, the main yam sapogenin, the steroid diosgenin, had no effect on foraging behaviour, and tomatin, a steroid-alkaloidal saponin, induced only long-term deterioration of the fungus garden when incorporated in the nest. The saponins tested are thus not detected by the ants and are therefore unable to initiate the strong and rapid foraging inhibition observed with resistant yams.