Figure 7 in The bibliography of and taxa proposed by Charles D. Michener

Figure 7. Cover of Michener's 1944 publication resulting from his doctoral dissertation at the University of California, Berkeley [dissertation, The External Morphology and the Phylogeny of Bees ([i]+190 pp., +15 pls.), awarded December 1941, and undertaken under the supervision of the preëminent Edward O. Essig (1884–1964)]. This work marked a dramatic turning point in the study of bee systematics, standardizing the morphological terminology employed and providing a revised classification, albeit largely structured around the North American fauna.