ABSTRACTA black yeast-like fungus was found to be commonly associated with provisions, larval gut contents and frass of alfalfa leafcutter bees (Megachile rotundata). The formation of dark colonies composed of hyphae developing chains of blastoconidia and cylindrical to barrel-shaped arthroconidia suggested an affinity toTrichosporonoidesorMoniliella.Although lacking the synchronously produced blastoconidial state demonstrated by the type speciesTrichosporonoides oedocephalis, the leafcutter bee fungus has been namedT. megachiliensisbecause of its morphological and physiological similarities withT. madida, T. nigrescensandT. spathulata.These species also lack the synchronously produced blastoconidia and are redescribed here. The recently describedT. australiensewas found to differ substantially from existing species in both morphology and physiology and is considered to be synonymous withBrettanomyces anomalus(anamorph ofDekkera anomala). A key to the species ofTrichosporonoidesandMoniliellais provided.