THE POLLINATION ECOLOGY OF DICENTRA CUCULLARIA

Abstract

In northeastern Iowa and southwestern Wisconsin the flowers of Dicentra cucullaria were fotund to be pollinated almost exclusively by Bombus bimaculatus nectar-foraging queens, which were phenologically synchronized in their emergence from hibernation with the flower's anthesis. Cinematographic and stereophotographic evidence indicated that pollen transfer was effected by the ventral side of the insect's head and anterior thorax contacting essential flower parts and to a lesser degree by the front and middle legs contacting pollen-laden edges of the inner petals. Lepidoptera, Diptera, and small Hymenoptera occasionally encountered on the flowers were ineffective in pollination. Abundant Apis mellifera pollen-foraging workers regularly effected pollination, but being an introduced species it exhibits no naturally developed pollination adaptatioin to the flower. Nectar spur perforation by B. affinis nectar-foraging queens did not affect plant fertility, and this behavior was related only in part to forager tongue length. Nectar-foraging behavior of B. bimaculatus queens on the flowers was correlated with the phenological development of the annual insect colonies. DICENTRA CUCULLARIA (L.) Bernh. is a spring ephnm-ral h-rb growing in the rich moist soil of deciduous forests of northeastern temperate North America with a disjunct distribution