The mesmerizing wart: the pollination strategy of epiphytic lady slipper orchid Paphiopedilum villosum (Lindl.) Stein (Orchidaceae)

Paphiopedilum uillosum was studied in hill evergreen forests (at up to 35 m above ground level) in North Thailand between 1990 and 1994. Flowering lasted 4.5 months: flower longevity 2–3 months. During 224 hours of flower‐watching, less than 100 specimens of Syrphidae (Diptera) were seen in the vicinity of the flowers; 15 cases of pollen acquisition were mainly by female Eplsyrphus alternans, Syrphus fulvifacies, Betasyrphus serarius among 6 spp. of pollinators. Populations peaked during the main flower opening period, one month before the maximum number of open flowers was reached in early February. The flowers are ‘kettle‐traps’ without known reward, luring mainly by food deception. Long distance attraction is probably by a urine‐like odour (attraction to mammalian excretions had hitherto been little reported) and colour contrast. Close range lure is by the glittering staminode (probably mimicking droplets of honeydew/moisture) centred by a slippery wart (faking a perch) at which pollinators fly, immediately losing their grip and tumbling into the pouch, preventing wing action and falling being disrupted by a trough‐shaped frame. Escape is up the tunnel, past the stigma, to the exit where, pressed by several mechanisms against the anther, the hoverfly scoops off very sticky pollen which has a viability of at least 8 weeks. Capsule formation averaged 8%.