Moldy Choice

Orchids are freewheeling members of plant society. Some hang about in trees, accepting any handout that comes their way. Others are more down to earth, and put down roots. Even these are not trustworthy.

When plants require insects for pollination work, they offer a reward in the form of nectar for a job well done. Orchids are more slippery than that, as they make promises of food or sex to naïve insects with no intention of honoring the deal.

The latest con trick to be studied is with the slipper orchid Cypripedium fargesii found in China. The study by Ren et al is published in The Proceedings of the National Academy of Sciences (1). The chosen mark for the con trick in this case is the flat-footed fly which spends its lowly life munching on mold spores found in rotting vegetation.

The business end of the orchid has lots of little black spots that to you, me or a flat-footed fly look like black mold spores, laid out in a trail promising greater delights to those following it to the source deep within the flower. Exuding from the depths of the slipper comes the tantalizing odor of rotting vegetation with the promise of an abundance of tasty spores. The entrance is low so to get to the feast the fly has to brush against the orchid’s anthers and collects a pollen load but there is no lunch to be found. The hungry fly now rushes to the next promise offered by a nearby slipper. The only ones to get any benefits are the Cypripediums who are now sexually replete while the flatfoots are stomping around in a ravenous state.

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