Pollination of the Small White Lady's-slipper (Cypripedium candidum) in Lambton County, southern Ontario

Abstract

Andrenid and halictine bees 6-7 mm in length appear to be the most important pollinators of Cypripedium candidum in a native prairie. Experiments indicate that effective pollinator size is restricted by the dimensions of the entrance and exit passages of the semi-trap blossom. On the path of escape the dorsal surface of the thorax of the appropriate bee-pollinator will come into contact first with the stigmatic surface and subsequently with the anther. Three Andrena ziziae females, one female of a Sphecodes sp., one female of a Nomada sp., a small hymenopterous parasite (Chalcidadae), and a beetle (Elateridae) were found inside flowers. Females of Augochlorella striata, Halictus confusus, Dialictus rohweri, D. atlanticus, and D. pilosus were observed carrying C. candidum pollen on the dorsal surface of the thorax. A local diversity of wildflowers may influence the fecundity of C. candidum through its effect on abundance and diversity of pollinators.