ABSTRACTThe recently described solitary bee Monoeca catarina Aguiar (Apidae, Tapinotaspidini) is only known from two nest aggregations on Santa Catarina Island, state of Santa Catarina, southern Brazil. Nests are excavated in sandy soils along trails near dunes and beaches. Up to 287 nests were counted in one aggregation. Bees were active for about seven weeks from late November to mid-January suggesting a univoltine life cycle. Males perform patrolling flights over the nest area and mate with females sitting on low vegetation. Males and females visited Stachytarpheta cayennensis (Verbenaceae) for nectar, and females were observed foraging on Tetrapterys sp. or Heteropterys sp. flowers (Malpighiaceae). Pollen loads consisted almost exclusively of Malpighiaceae pollen. Potential natural enemies are the cleptoparasitic bee Protosiris Roig-Alsina sp. (Apidae, Osirini) recorded within the aggregations, and the mutillid wasp Hoplocrates specularis (Gerstaecker) (Mutillidae, Sphaeropthalmini) seen entering the Monoeca nests and mating within the aggregations. Except for the soil characteristics, our observations on nesting and foraging behavior and associated potential enemies fit well into the facts reported from other Monoeca species.