Here we focus on Cypripedium fargesii, a critically endangered species endemic to southwestern China (18), to elucidate its mechanism of floral mimesis and to interpret the function of black spots on its leaves. In this species, each short flowering stem bears two leaves with rows of black spots on the upper surfaces (Fig. 1 A and B). The stem terminates in a small, solitary, dark-red to dull-yellow flower that produces a faint but unpleasant odor reminiscent of rotting leaves. We examined flower and leaf traits and conducted hand-pollination experiments to identify the breeding system. We tested embryo viability using a modified tetrazolium method (19). Pollinators were observed, captured by clogging floral apertures, and identified (20). Floral scent was collected outdoors by dynamic headspace adsorption methods and analyzed by GC-MS.