Of bog orchids and bloodsuckers

July 30th 2018

Earlier this summer, Iain Macdonald paid me an unexpected visit at Nedd.  Raised at Culkein Drumbeg, but now living over on the east coast, he is an experienced botanist. He reminded me that, over twenty years ago, he had found bog orchid Hammarbya paludosain a mire just off the road between Nedd and Drumbeg (NC132325).  This area is dominated in places by tussocks of black bog-rush Schoenus nigricans.  It is not named on the 1:25,000 O.S. map, but the late Colleen MacCrimmon of Nedd called it Poll Buidhe (yellow hollow or mire), a reference perhaps to the silvery-yellow hue assumed by black bog-rush in the autumn.

Bog orchid is the least conspicuous of our local orchids, with tiny green flowers in a spike that rarely exceeds 10cm in height.  This is one of only five places in Assynt where it has been found, although not at any of them this century.  I must have walked or driven past the area many hundreds of times, but had not paid it any recent attention.

On 11thJune, Gwen Richards and I thought we might have a look for the orchid, and spent over an hour combing the margins of its pools and hollows.  Unfortunately, the recent hot weather had dried out much of the mire.  This did not prevent me getting a boot-full of very smelly water, but it was difficult to find suitable sites for the orchid, which, in my limited experience, likes really damp, base-flushed, open areas. So the primary aim of our visit was frustrated.

However, the expedition was not without interest.  Gwen noticed a horse leech Haemopsis sanguisuga attacking a large black slug Arion ater on the well-vegetated surface of one of the pools. Horse leeches are by far the largest of those found locally, reaching up to 60mm at rest, and perhaps twice as much extended. They have strong jaws but, despite their name, prey exclusively on ‘almost any invertebrate, swallowing whole those that are small enough, and sucking the blood of larger ones’, such as the hapless slug.  They do not attack horses or any other mammals.

On the marshy fringes of the site we found early marsh and lesser butterfly orchids.  Beside the remaining pools there were large red damselflies Pyrrhosoma nymphula, emerging froglets and, over one of the largest, patrolling adult four-spotted chasers Libellula quadrimaculata, with an exuvium nearby. And, just as we got back to the car, an early dark-green fritillary flew at speed across the road.

Ian M. Evans

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