Res. Popul. Ecol.(1985) 27, 373-392. 9 by the Society of PopulationEcology FORAGING BEHAVIOR OF INDIVIDUAL WORKERS AND FORAGING DYNAMICS OF COLONIES OF THREE SUMATRAN STINGLESS BEES t,2) Tamiji INOUE*, Siti SALMAH**, Idrus ABBAS** and Erniwati YusuF*** * Entomological Laboratory, College of Agriculture, Kyoto University, Kyoto 606,Japan ** Department of Biology,Faculty of Science, Andalas University, Padang, Sumatera Barat, Indonesia *** Bogor ZoologicalMuseum, P.O. Box 110, Bogor, Indonesia INTRODUCTION The two groups of highly eusocial bees, honeybees (Apis) and stingless bees (Meliponini) are both rich in pollinator assemblages of Southeast Asia. About 50 species of stingless bees are recorded (SAKAGAMI, 1982) and 6 species of honeybees (MAA, 1953; SAKAOAiI et al., 1982). Twenty two stingless bee and three honeybee species have been found in Sumatera Barat, at the site of this study. Here, 5 stingless bee species and all the honeybee species inhabit continuously-disturbed areas such as orchards and villages and the remaining stingless bees are found mainly in primary rain forests. In both areas stingless bees are major visitors of various flowering plants. Foraging behavior of stingless bees has been mainly studied in Central and South America: LINDAUER and KERR (1958, 1960), KERR and ESCH (1965) and the other works which are reviewed by MICHENER (1974) studied their resource communication behavior, and JOHNSON and HUBBELL (1974, 1975), HUBBELL and JOHNSON (1977, 1978), ROUmK (1978, 1979, 1980, 1981, 1982), ROUBIK and ALUJA (1983) and ROUBIK and BUCHMANN (1984) observed patterns ofinterspecific resource partitioning. However, no observation of stingless bees' foraging behavior has been made in Southeast Asia (but see KOENIGER and VORWOHL, 1979 in Sri Lanka). In most of the above studies, the patterns of foragers' visits and changes in standing crops of floral resources were observed mainly on flowers or feeders. These approaches are convenient to observe direct interactions on floral resources. In this study, however, observations are made mainly at nest entrances, by counting the number of foragers which go out from and come back to a nest, and measuring the amount of resources brought back per foraging flight and the foraging durations of individual foragers. By these observations, the foraging behavior of individual workers and foraging dynamics of entire colonies is clarified in three Sumatran stingless bees which live in disturbed areas. At the same time, the intensity of competition against floral resources is indirectly assessed. 1) Contribution to the ecological and bioeconomicalstudies of the sfingless bees. 4. 2) Contribution No. 17 of Sumatra Nature Study (Entomology).