Ophrys speculum is a species of orchid found in the Mediterranean which mimics the virgin female of a scoliid wasp - Campsocolia ciliata. The mirror orchid produces many volatiles organic compounds that together, are exceptionally similar to the pheromones produced by female wasps prior to copulation. In addition, the colours and shape of the labellum (the landing platform for the wasp) also show great similarity to the wasps in order to attract them for pollination. Studies have found that when both the orchid and the virgin female wasps are present in one area, the orchid is more successful in attracting the males. This is possibly due to the greater range of pheromones that they possess of which some may have a different means of attracting the males. This is a phenomenon which I think is incredibly interesting and I was lucky enough to see it in action in Mallorca. I always wonder how the orchids evolved this mimicry and why the wasps are still attracted to the orchids, despite there being no benefit to themselves - known as 'pseudocopulation'. This process also occurs in other mimicry orchids, including Ophrys apifera (bee orchid) which can be seen in the UK, as well as spider and fly orchids. It was suggested by Schiestl and Cozzolino that the pheromones produced did not initially have a role in sexually deceiving the male wasps but this later became it's main function. The initial role of a high range of volatiles likely evolved as they were scents preferred by pollinators. The higher production of the volatiles that mimic the female of the pollinator would have then later evolved. Ophrys speculum mimic the female wasps, rather than the males as males invest more time in mating (as females care for the brood) so the likelihood of a successful pollination event is increased.
In other studies, when male Campsocolia ciliata have been tracked, they do eventually seem to learn to avoid specific flowers that they have attempted to copulate with, after they've realised nothing was gained. So, if they learn to avoid, how does it persist? New males. These young and naïve wasps do not yet realise that the so-called 'female' is actually an orchid. These wasps are therefore the main pollinators of Ophrys speculum. As I saw in Mallorca, within the group of wasps present where the orchid was, only some of the males would attempt copulation but others would fly up to the flower and then fly off - as if they knew that it was a hoax. Also, they may not teach their young how to distinguish because that would take a lot more energy than the new males would spend learning themselves. Hopefully you have found this as amazing as I did - that a massive range of orchid species are able to mimic an insect so that they are pollinated, and without giving a reward to the pollinator too! If you get chance, you could try spotting some of the Ophrys apifera which are present in the UK, or the other mimicry species elsewhere and observe if the males are yet to overcome their innocence. ©
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