On a sunny day on 22nd March 2025, Roz and Andy Summers saw a mating mall of stone flies on a fencepost beside the Clashnessie burn NC055303. Closer examination showed up to five flightless males surrounding a solitary female.
The species was identified by Craig Macadam as Perlodes mortoni, an endemic species with a widespread distribution. There are no records of this species from Assynt so far, although there are some from Laxford to the north and near Lairg.
The photo shows males, with their macropterous wings. The females are fully winged. Criag described this as interesting behaviour – these stoneflies live as larvae in running water and when they emerge they tend to run up trees and bridges, etc., where they hide under the bark or in crevices. There’s not much of that around Clashnessie so it looks like they are using the fencepost as a surrogate habitat. Stoneflies are often found on fence posts, in fact, it’s one of the best ways to find them at this time of year.
Andy Summers