Contribution toward a monograph of the genus Ascosphaera
Cultures and herbarium collections of the previously described species of Ascosphaera were studied. Additional observations are reported on Ascosphaera strains associated with the alfalfa leaf-cutting bee, Megachile rotundata (Fab.). Three new species of Ascosphaera are described, all occurring in brood cells of the alfalfa leaf-cutting bee. Ascosphaera larvis sp.nov., with short, ellipsoidal ascospores, was frequently associated with a chalkbrood-like disease in early-instar larvae. Ascosphaera pollenicola sp.nov., a homothallic species with subcylindric ascospores, most often occurred on pollen provisions in brood cells. Ascosphaera variegata sp.nov., with conspicuously mottled ascomatal walls, was isolated from pollen and also from larvae that had died from undetermined causes. Descriptions and an identification key are provided for the 11 species of Ascosphaera currently recognized.