Bumble Bees of North America: An Identification Guide. 2014. Williams, P; Thorp, R; Richardson L & Colla, S. Princeton University Press.
Bumble Bees of the Eastern United States. 2011. Colla, S; Richardson, L & Williams, P. USDA Forest Service and the Pollinator Partnership.
Minnesota Bee Atlas - online bumble bee tutorial, flashcards, and species identification slides. University of Minnesota Extension.
Bee Spotter Keys to Bumble Bees of Illinois, Missouri, Ohio, and Indiana.
Bumble Bee Watch - species identification key and anatomy resources.
Wisconsin Wild Bee Guide. University of Wisconsin Great Lakes Bioenergy Research Center.
Bumble Bee Identification Guide. Discover Life.
Bumble Bees of Wisconsin. University of Wisconsin-Madison