The pollination biology of Aspidogyne argentea, Aspidogyne longicornu and Erythrodes arietina was studied in southeastern Brazil. The three species are self-compatible but are pollinator-dependent, These three orchid species offer nectar as a reward to pollinators and flower visitors. The two Aspidogyne spp. have a dorsally-adhesive viscidium, a feature which precludes pollinators other than bees. Erythrodes arietina flowers are protandrous and show a ventrally-adhesive viscidium. Aspidogyne argentea is visited by halictid bees (here ranked as probable pollinators) and Hesperiidae butterflies. Aspidogyne longicornu is pollinated by females of Euglossa (Euglossini) and visited by the hummingbird Phaethornis ruber and by the euglossine bees Eulaema seabrai (females) and Eulaema cingulata (males). The pollinarium adheres to the ventral surface of the bee labrum, a very difficult place for bees to clean. The dorsally adhesive viscidium in Aspidogyne parallels that of the Spiranthinae genera of the so-called 'Pelexia alliance'. This condition seems to be particularly adaptative under conditions of low-frequency pollinator visits. Erythrodes arietina is pollinated by bees of the genera Puratetrapedia and Osiris which carry the pollinarium on the dorsal surface of their proboscis. Occasionally. these bees remove pollinaria from their mouthparts using their forelegs. In general, in the species studied, a combination of both pollinator behaviour and morphological peculiarities promotes cross-pollination, (C) 2001 Annals of Botany Company.886989997