For the first time the pollination of a poorly known, terrestrial orchid, Habenaria pleiophylla Hoehne & Schlechter, 1921 (Orchidaceae) by a passion vine butterfly, Heliconius erato phyllis (Fabricius, 1775) (Lepidoptera, Nymphalidae) is reported. Number of pollinia-carrying individuals was determined on a population of H. erato phyllis in Horto Florestal Barba Negra, Barra do Ribeiro County, Rio Grande do Sul State. The pollination mechanism was described under laboratory conditions, in association with the butterfly feeding habit and the orchid flower morphology. Habenaria pleiophylla pollinia are cemented during nectar feeding on the ventral portion of the compound eyes near H. erato phyllis proboscis base. The pollinia are transferred to the stigma of other flowers during subsequent visits. Both males and females of H. eralo phyllis frequently visit H. pleiophylla flowers in the Barba Negra Forest. About forty percent of field collected adults had attached pollinia, ranging in number from one to 19 per individual. Thus, H. eralo phyllis may play an important role in the reproductive biology of this H. pleiophylla population.
Nymphalidae; Heliconius; Orchidaceae; Habenaria; pollination