Beyond the razzmatazz of the pier and amusement arcades lies a quieter seaside attraction that escaped the attention of most visitors who flocked to this north Lincolnshire resort during the recent heatwave. The sand dunes in the local nature reserve host a fine display of marsh orchids. We counted over 200 of their conical magenta inflorescences in one flowery dune slack that was no larger than a tennis court. Peacock, small tortoiseshell and common blue butterflies, shimmering in a mirage of midday heat, flitted among them but their attention seemed mainly drawn to vetches, hawkweeds and hay rattle blooms, rather than the orchids' densely packed floral temptations.
A check inside the flowers revealed that in most the pollinia – the paired stamens that are inadvertently collected by butterflies and moths, and carried in their entirety between flowers – were intact. Charles Darwin, in his study of orchid pollination, called these "beautiful contrivances" and described how to mimic the action of a butterfly's proboscis by poking a sharp pencil into the flower's nectar spur, then withdrawing it with a sticky pollinium attached.
I followed his instructions, but with a fine twig, and extracted a pollinium, a tiny club-shaped package of pollen that the orchid had advertised with so much floral extravagance and offered with a nectar reward for any visitor that could be conned into carrying it away. I watched this "beautiful contrivance" until the extracted pollinium, first vertical, slowly bent forward in the sun's heat, just as Darwin said, until it was perfectly positioned to contact a receptive stigma when carried to another flower. So why had the butterflies collected so few pollinia? Darwin had an answer. He counted the individual pollen grains in a single pollinium and found each contained enough to sire over 120,000 seeds. A few successful collections among this dense orchid floral display would be enough. Such is the profligacy of natural selection.
