An entry written by Taisha:
Today's photo is of Coryanthes thivii, sometimes known as Thiv's coryanthes. It was photographed by douneika@Flickr at Viridalia 2013 (a horticultural event at Castello di Thiene in Italy). The image was contributed via the Botany Photo of the Day Flickr Pool. Thank you douneika!
Thiv's coryanthes is an epiphytic orchid species native to Bolivia, where it grows in humid lowland forests. Coryanthes as a group are known more commonly as the bucket orchids. Species from this genus are known to grow in what are called ant-gardens, which is an example of a mutualistic relationship. The orchids provide both nectar for the ants from extrafloral nectaries and a framework for ant-nest construction within the matrix of their root system, while the ants defend the orchid against herbivory and disperse the seeds of the orchid.
The pollination mechanism for this genus is also notable. Pollination in Coryanthes is carried out exclusively by male euglossine bees. The male bees are perfume-collectors who gather fragrant oils to attract females. In this orchid genus, the anthers and stigma are spatially separated. When the male bees are collecting the fragrance compounds, they fall into the liquid-filled bucket (hence, bucket orchids). The now-wet wings prevent the bees from flying to escape, while the slippery sides of the bucket force a single mode of exit. The bee must climb a column and out a passage formed by the column apex and the labellum. When exiting, pollinia from previous flower visits that were attached to the back of the bee may transfer to the stigma of the flower by the bee's forward movement. After the bee moves through the area of pollinia transfer, it still needs to struggle a bit to exit the flower and consequently may have pollinaia from this flower attach to its back. After drying off, the bee will often then visit another flower and repeat the process (see: Gerlach, G. 2011. The genus Coryanthes: A paradigm in ecology. (PDF) Lankesteriana. 11(3):253-264.).