Interaction of visual and olfactory stimuli determining orientation of Papilio demoleus larvae

Abstract

An attractant visual source (foliage green paper) and an attractant odour source (citral) were presented in different combinations to Papilio demoleus larvae. The larval orientation to these sources of stimuli was determined by their interaction which varied with their combination pattern. The orientational preference of the larvae, offered a choice between the visual and the odour sources in two opposite directions, depended upon their stimulating capacities which were represented by the percentages of individuals responding to the sources of stimuli presented singly. When the stimulating capacities of the two sources were equivalents of 50% or greater larval turning, the larvae always showed a preference for the visual source irrespective of the stimulating capacity of the odour source. However, when the stimulating capacity of the visual source was the equivalent of below 50% larval turning, the larvae would exhibit a preference for the odour source if its stimulating capacity was substantially higher than that of the visual source. Thus, the visual attractant was much more dominant than the odourous attractant when the two competed with each other. On combining the visual and the odour sources together on the same side, the two had a synergistic action in attracting the larvae. The visual-cum-odour source was preferred to a visual source when the two were presented together from opposite directions. On presenting the visual, odour, or visual-cum-odour sources on one side of the larvae released on the host plant leaf-sheet, the insects were drawn away from it by the sources of stimuli after feeding to satiety. The visual-cum-odour source was most effective in drawing away otherwise resting larvae from their host plant leaves.