A four-year field study conducted in southwest Oregon field sites examined the relationships between blooming Cypripedium fasciculatum and associated insect visitors. C. fasciculatum has a one-way pollinator path that will accommodate insects of 5 mm or less, offers no nectar reward, and dispenses a bilobed pollen mass from each of two anthers. Insect visitors in the field sites were monitored primarily with sticky cards. Diapriid wasps (sub-family Belytinae) in the genus Cinetus were the only insects found vectoring C. fasciculatum pollen. Intact pollen masses were examined using scanning electron microscopy (SEM). C. fasciculatum pollen was always situated as a single or double mass on the sculpted mesonotum of female Cinetus wasps.
Belytines are documented parasites of fungus gnat larvae and pupae, and Sciarids have consistently been the most abundant insects captured in Oregon orchid sites. Diapriids were captured in orchid field sites prior to orchid emergence, but peak diapriid activity corresponded to peak orchid bloom in May. Diapriid activity declined abruptly by mid-June. Numbers of captured fungus gnats were steady throughout the cool and damp spring.
Diapriids are presumably attracted to C. fasciculatum by deceit, probably by scent. C. fasciculatum odor is inconsistently noticeable during the blooming season and the chemical composition of the odor has yet to be analyzed. Possible sources of the odor on the orchid were examined using SEM.
Species 1: Hymenoptera Diapriidae Cinetus sp
Species 2: Orchidaceae Cypripedium fasciculatum (Clustered lady-slipper)
Species 3: Diptera Sciaridae (dark-winged fungus gnats)
Keywords: orchid pollination, orchid pollen
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