We report on the feeding by black bears on harvestmen (Opiliones). Two scats of black bears from Sonora, Mexico each had over 50 bodies of a species of Leiobunum C.L. Koch, 1839 collected in localities separated by 5 km. Microsatellite analysis indicated that the scats were from different individuals. That all harvestmen were found in only two of the 180 scats sampled suggested that the two bears fed on harvestmen while in aggregations. Because black bears are probably minimally affected by defensive compounds and would presumably not actively search for individual harvestmen, black bear predation on harvestmen, if frequent enough, would be a factor selecting against aggregative behavior in these arachnids in the study area. Further research is needed on the aggregation behavior and other natural enemies of harvestmen in northwestern Mexico.