Fig. 1.

Stereotyped floral morphology of the ∼1,300 species of New World Malpighiaceae showing the prominent dorsal banner petal that is highly differentiated from the other four petals (A). All petals are conspicuously clawed at the base (A), which allows their primary oil-bee pollinators access to the large paired, multicellular abaxial oil glands, borne on four or all five of the sepals (B) (15, 25). A female oil bee orients toward the banner petal (C) and lands at the center of the flower and grasps the thickened claw of that petal with her mandibles (D). She then reaches between the claws of the lateral petals and scrapes the oil from the glands with her modified front and mid legs. She then transfers the oil and pollen to her hairy hind legs and takes the mixture to her nest, where it serves in nest construction and as food for her larvae. A and B are of Mezia angelica W. R. Anderson, courtesy of C. Gracie (New York Botanical Garden). C and D are of a Centridini oil bee visiting Malpighia emarginata DC, courtesy of G. Gerlach (Munich Botanical Garden, Munich).