Abstract
A field study of the floral biology of Victoria amazonica (Poepp.) Sowerby (Nymphaeaceae) was made for comparison with the many studies made in cultivated plants, of Victoria in the past. In the study areas in the vicinity of Manaus, four species of Dynastid beetles were found in flowers of V. amazonica, three of the genus Cyclocephala and one of Ligyrus. The commonest species of beetle proved to be a new species of Cyclocephala and was found in over 90 percent of the flowers studied. The flowers of V. amazonica attract beetles by their odour and their white colour on the first day that they open. The beetles are trapped in the flower for twenty-four hours and feed on the starchy carpellary appendages. Observations were made of flower temperature, which is elevated up to 11°C above ambient temperature, when the flower emits the odour to attract the beetles. Observations on beetle frequency, the number of floral parts, seed dispersal and the evolutionary development of cantharophily are also presented.