Sleep aggregations have been registered for some species of solitary bees and wasps. In this note we describe the aggregation behaviour of Centris xanthomelaena Moure & Castro bees in their inactive periods. The dormitories were discovered close to the bee nesting sites, in a Caatinga area. We monitored the males and females at the sleeping site for 16 consecutive days in July 2017. We observed that females of C. xanthomelaena spent the night outside their nests, indry branches of Mimosa tenuifl ora (Fabaceae). Furthermore, males and females have shared the dormitories, and sometimes they formed mixed ones. Both males and females fl ew around the nearest dormitories during all observation days. The data about the sleep behaviour of C. xanthomelaena will contribute to the understanding of these aspects within the Centris genus.