Report Orchid Mimics Honey Bee Alarm Pheromone in Order to Attract Hornets for Pollination

Abstract

Summary Approximately one-third of the world's estimated 30,000 orchid species are deceptive and do not reward their pollinators with nectar or pollen Results and Discussion The Orchid and Its Pollinator In this study, we investigated the floral scent involved in pollinator attraction of the rewardless orchid Dendrobium sinense, a species endemic to the Chinese island Hainan During the flowering time of D. sinense, there are two other sympatrically occurring orchids in bloom, Epigeneium fargesii and Coelogyne fimbriata. Hornets are not interested in the flowers of C. fimbriata but occasionally visit the flowers of E. fargesii. However, we never observed them to remove pollinia (S.X.-q., unpublished data). Therefore, the pollinia that the hornets carry are definitely from D. sinense. This result supports that V. bicolor is the pollinator of D. sinense. Our observations led us to hypothesize that V. bicolor is the sole pollinator of the orchid D. sinense. This hypothesis is supported by a comparison of the pollinator and orchid flower size Hornets belong to the group of social wasps that feed their brood with meat nutriments, mainly insects In a recent study, flowers of Epipactis helleborine, another wasp-pollinated orchid, were shown to emit green-leaf volatiles (GLVs), which are attractive to the foraging social wasps Vespula germanica and V. vulgaris Is the Floral Scent of the Orchid Attractive to Hornets? To investigate the relative importance of floral signals to foraging hornets, we compared the attractiveness of singl