Insect visitors to extrafloral nectaries of Byttneria aculeata (Sterculiaceae): relative importance and roles

Abstract. 1. Ants, parasitoids and flies are about equally frequent at foliar nectaries of Byttneria aculeata (Sterculiaceae) in lowland Costa Rica during the dry season, a pattern previously unreported but also observed at other plants in the area.
2. Species of Ectatomma, Crematogaster and Camponotus were the most frequent of twenty-four ant species on Byttneria, eight of which nested in the hollow stems. Ants spent most time at nectaries and little in patrolling.
3. Collections at nectaries yielded large numbers of species of parasitoid Hymenoptera with few individuals of each. Rearing studies of leaf-feeding herbivores yielded several species of parasitoids, including one species taken at a nectary and two others congeneric or closely related.
4. Flies appear to be nectar thieves, in the same sense as non-pollinating floral visitors, despite close association with Byttneria.
5. Ant-plants may be poor models for the larger number of species of less specialized plants with extrafloral nectaries. Plants which have only extrafloral nectaries may better suit the needs of parasitoids than ants, and plants such as Byttneria may benefit as much from parasitoids as from ants.