Butterfly pollination of Caesalpinia pulcherrima, with observations on a psychophilous syndrome

(1) Butterflies are the primary pollinators of Caesalpinia pulcherrima and the pollen is carried primarily on their wings. Of the numerous species that visit the flowers, members of Papilionidae are the most important pollinators. (2) The Papilionidae approach the flowers from above and in front, thus maximizing anther- and/or stigma-wing contact, and they are effective pollinators because they flutter their wings continuously while visiting a flower. (3) The behaviour of species in other families results in smaller pollen loads and fewer anther- and/or stigma-pollinator interactions. (4) Foraging visits of all butterflies are proportional to the volume of accumulated nectar. Where visits are numerous, they are brief; where visits are few, they are longer. (5) The pollen grains are held together by viscin threads, which results in the pollen having a clumped dispersion-pattern on the butterfly wing. (6) Cross-pollination is facilitated by the stigmas being exserted further than the anthers and by the butterflies visiting only four to six flowers per tree on any foraging trip. (7) The flowers of C. pulcherrima are similar to other species pollinated by butterflies, in that access to the nectar is indicated by a yellow `target' in a red background.