Behavioral foraging responses by the butterfly Heliconius melpomene to Lantana camara floral scent

Floral color has been shown to influence flower selection by butterflies, but few studies have investigated the role of floral scent. In this study, adults of Heliconius melpomene L. ( Lepidoptera: Nymphalidae: Heliconiinae) were tested in two-choice bioassays to investigate their ability to distinguish floral scent of the butterfly pollinated plant Lantana camara L. ( Verbenaceae) from other plant scents. The relative importance of floral scent vs. color was also studied. Butterfly foraging behavior was measured as probing with proboscis. This probing, on floral models varying in scent and color, was timed. When given a choice of floral and vegetative scents of L. camara, newly emerged butterflies preferred floral scent, indicating an innate response to floral scents. When butterflies were conditioned to L. camara floral scent by offering the scent with yellow color and sugar water, yellow color elicited stronger feeding responses than did the floral scent. However, the floral scent of L. camara was preferred to that of the novel species Philadelphus coronarius L. (Hydrangiaceae). The floral scent of L. camara was dominated by tepenoid compounds, while that of P. coronarius by fatty acid derivatives, thus demonstrating totally different compositions. It is concluded that, while H. melpomene butterflies often use visual floral traits when selecting which flowers to visit, floral scents elicit behavioral responses that initiate and maintain foraging on flowers.