Bumble Bees of North AmericaPaul H. Williams, Robbin W. Thorp, Leif L. Richardson, Sheila R. Colla · First published 2014Open the Tome
Bumble Bees Of North America An Identification GuideRobbin W. Thorp · First published 2014Open the Tome
Bumble bees and cuckoo bumble bees of California (Hymenoptera, Apidae)Robbin W. Thorp · First published 1983Open the Tome
Systematics and ecology of bees of the subgenus Diandrena (Hymenoptera: Andrenidae)Robbin W. Thorp · First published 1969Open the Tome
