THE POLLINATION ECOLOGY OF BLETILLA-STRIATA (ORCHIDACEAE)

Anthecological observations of an orchid Bletilla striata were carried out in Kobe, Japan. The purplish pink flowers were visited by 26 species of insects belonging to Hymenoptera, Diptera and Lepidoptera, although the flower did nor offer food rewards of any kind. Candidates for pollination were seven species of aculeate Hymenoptera with a body size that: well fitted the space in between the column and labellum. The most effective candidate was the male of the longhorn bee Tetralonia nipponensis, judging from its abundance and legitimate intrafloral behavior. The female of T. nipponensis and the other six species also contributed to promote out-crossing, but to a lesser extent than the male T. nipponensis, since they occasionally exhibited illegitimate intrafloral behaviors for pollination and also, their flower visitation rate was lower.