The sources consumed byNannotrigona testaceicornis(Na),Trigona (Tetragonisca) angustula(Te),Scaptotrigona mexicana(Sc) andPlebeiasp. (Pl) were studied at two localities in southeast Mexico: Unión Juárez (U.J.) and Santa Teresita (S.T.), by means of melissopalynological analyse of pollen, honey and larval food. A total of 246 samples were collected in an annual cycle from April (1987) to March (1988). The analyse showed that these native bees are polylectic. At U.J., 54 species of plants were important and there was an overlap of trophic niches in the four bee species when they collected nectar and pollen fromAgeratum houstonianun, Alchornea latifolia, Tremna micrantha, Coffea arabicaandCitrus limon. Two bee species foraged at 12 plant taxa, includingIresine celosia(Sc, Te),Vernonia canescens(Sc, Pl),Cercidium praecox(Na, Sc). At S.T. 65 taxa were important with an overlap in (Na, Te, Sc and Pl) at one nectaropolliniferous species:Sapindus saponaria. Three native bees collected atSpondias purpurea(Na, Pl, Sc) andPetiveria alliaceae(Na, Pl, Te). An overlap between two bee species occurred in 8 plant species. These includedMimosa orthocarpa(Na, Sc),Celtis iguanaea(Te, Na),Crossopetalum parvifolium(Sc, Te) andHeliocarpus donnell-smithii(Na, Pl). At both localities each bee species showed a preference for certain plants. In the larval food nectaropolliniferous and polliniferous species were important and three principal nourishment mechanisms were observed. Finally, swarming was only detected in Na at both localities from September (1987) to February (1988).