Wings of Osmiini. a, Ashmeadiella bucconis (Say); b, Atoposmia (Hexosmia) copelandica (Cockerell); c, d, Portions of forewings of Chelostoma (Prochelostoma) philadelphi (Robertson) and Osmia (Osmia) lignaria Say, showing diversity in stigma size (source: Michener, 2007)