Owen, Robin E., and Troy L. Whidden. “Discrimination of the Bumble Bee Species Bombus occidentalis Greene and B. terricola Kirby by Morphometric, Colour and RAPD Variation”. Zootaxa 3608, no. 5 (January 22, 2013): 328–344. Accessed July 5, 2025. https://www.mapress.com/zt/article/view/zootaxa.3608.5.2.