Tropical pitcher plants, Nepenthes, have been the subject of substantial scientific scrutiny for their prey digestion, but other aspects of their biology, particularly their reproductive ecology have garnered much less attention. I studied the three species of Nepenthes present in Johore, Malaysia and Singapore, N. gracilis, N. ampullaria and N. rafflesiana , to determine if there are significant differences among species in phenology, floral and nectar characteristics and pollinators. Differences in flowering period represents at best a partial barrier to cross-pollination among species. Each species has three flowering periods between January and July, but the timing of these episodes is offset among species such that at any given time one, two or all three species are in flower. Floral presentation differs among species in such characters as the number of flowers per inflorescence, flower size and color and sepal shape. N. ampullaria flowers present pollen during the day, while the other two species open their flowers in the evening. Nectar is produced nocturnally in all three species, but they differ in sugar composition and quantity of nectar produced. These differences suggest the species are adapted to attract different suites of pollinators. All species are pollinated by moths and small Diptera, but to differing degrees. N. rafflesiana is pollinated almost entirely by moths and all of its pollination is nocturnal. N. gracilis is pollinated almost equally by moths and small Diptera at night and also by wasps during the night and day. By day, N. ampullaria flowers have a foul odor and are pollinated by large flies, wasps and butterflies. The flowers produce a sweet odor at night and are then visited by moths. These differences are significant between species, but are still not sufficient to constitute a complete barrier to cross-pollination.

Key words: carnivorous plants, dioecy, entomophily, Nepenthes, phenology, pollination, vines