Records are presented on twenty nests of Megachile pugnata Say obtained from sumac stick trap-nests. These nests were distinctive as, unlike most Megachile nests, the cells were not constructed from pieces of cut leaf. Instead, the cells were made with basal and apical partitions consisting of leaf discs, chewed leaf materials and soil. Each finished nest contained an empty vestibule and had an orifice plug. The sequences of males and females, and the natural enemies of this species were determined by rearings. Females normally preceded males in the sequence of cells. The species was parasitized by Coelioxys alternata Say and Leucospis affinis Say. The mean number of cells in the nests was 3.5. There is one generation a year in Wisconsin.