POLLINATION BIOLOGY OF PLATANTHERA STRICTA (ORCHIDACEAE) IN OLYMPIC NATIONAL PARK,WASHINGTON

Platanthera striata Lindley is entomophilous and can produce seed via facultative self-pollination and intraracemic and interracemic pollination. Capsule production is pollinator-limited and seed set may be pollen-limited. In experimental plants capsules produced via self- and intraracemic pollination contained fewer seeds with normally developed embryos than did capsules produced via interracemic pollination. The inflorescence of Platanthera stricta is fragrant and is attractive to a wide array of anthophilous insects. It is pollinated by a diverse assemblage of short-tongued insects. The primary pollinators are Eustroma fasciata B. and McD. (Lepidoptera: Geometridae), Bombus flavifrons Cresson and B. melanopygus Nylander (Hymenoptera: Apidae), an undescribed species of Greya (Lepidoptera: Prodixidae), and several species of Empis, Rhamphomyia, and Anthepiscopus longipalpis Melander (Diptera: Empididae). Small amounts of glucose are present on the raceme. The extrafloral glucose may retain small pollinators on the inflorescence until they locate the floral spur aperture.