A slim fast moving centipede or rocks high on the shore in Wales.
No interactions present.
This is probably Strigamia maritima. However the rare Hydroschendyla submarina (which I confess to never having seen) has similar number of leg pairs (high 40s in male, which this is - note swollen back legs)and has same general appearence. H submarina often inhabits in rock crevices on the coast, whereas Strigamia maritima typical associated with strandline on shingle (but not always!). If the forciples (poison claws) under the head and coxal pores on last legs are examined the two species are very different.
BMIG website: www.bmig.org.uk (centipedes, millipedes & woodlice)
BMIG Newsletters ~ www.bmig.org.uk/view/resource/bmig-newsletter
BMIG Bulletins ~ www.bmig.org.uk/view/resource/bmig-bulletin
Many thanks for your input on this Steve. There are no more/closer images to help with a certain ID so I guess it will remain a "probable" S. maritima, especially as it's the far commoner species - although the habitat - crawling over a massive limestone outcrop above a sandy shore (below the coastguard station at Rhossili) fits Hydroschendyla well from your description.
Nick Upton, naturalist and photographer.
This is almost certainly a Strigamia maritima male although, as Steve says, Hydroschendyla also has swollen last legs. Hydroschendyla is almost always found in crevices, often quite low down on the shore and the L.neritoides zone seems far more typical for Strigamia which can occur in a wide variety of littoral sites, usually around high water level.
There is no reason why H.submarina should not be found in the Rhossili area but the habitat for this one does not really fit and I have never seen it "in the open" like this.
Many thanks Geophilus. Yes, it was trundling around above the tide line in the neritoides zone, quite late in the day on west facing rocks - the lower part of the cliff face below the lighthouse at Rhossili - which only catch the sun at that time, with many Petrobius around. Good to know my initial ID is even more likely based on the habitat and behaviour.
Lat/Lng: 51.5672, -4.3004
OS grid ref: SS406878