Diagrams of proboscides of bees. a, Spread proboscis of a long-tongued bee; b, Maxilla of the same; c, Labium of a short-tongued, in this case colletid, bee, showing portions of maxillary cardines at the base; d, Maxilla of the same. From Michener, McGinley, and Danforth, 1994. (source: Michener, 2007)