Most butterfly species forage for nectar, which provides them with carbohydrates and to some degree other nutrients, such as lipids and amino acids (Boggs 1987). A small number of genera feed exclusively on rotting fruits and plant sap (DeVries et al. 1999). Some 40 passion vine butterfly species, belonging to the genus Heliconius Kluk and a closely related monospecific genus Laparus Billberg gather nutrients from pollen feeding (Brown 1981, Gilbert 1972). Although common in bees, wasps, flies and beetles (Roulston & Cane 2000, Thorpe 2000), pollen feeding is rare among lepidopterans. In order to collect pollen, adults scrape anthers with the proboscis and gather the grains. The pollen is then incubated in solution and the amino acid-rich solution is ingested. The empty pollen grains are eventually discarded (Gilbert 1972, Krenn & Penz 1998). Pollen feeding provides amino acids that are used for egg production and somatic maintenance in adult Heliconius (Dunlap-Pianka 1979, Gilbert 1972, 1991). The most common sources of pollen are flowers of species in the genera Psiguria Neck. ex Arn. and Gurania (Schltdl.) Cogn. (Cucurbitaceae). The home range of an individual Heliconius will encompass one to many pollen plants (Murawski & Gilbert 1986).