Stony river bank.
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In southern Europe Small Pincertails also have blue eyes, and the appendages of the two species look similar without close examination.
I find that one of the easiest features to see is the pale 'collar' over the top of the thorax, behind the head. On Small Pincertail this is unbroken, while on Large Pincertail it is interrupted with a narrow dark bar that joins the dark markings in the central part of the thorax with the black front of the thorax.
This feature can be seen in the photos in this link (but isn't highlighted), with a couple of other features marked as well:
Many thanks indeed Roy. This is really helpful. I have looked at the Guillaume Doucet website, which has lots of good photos - but where did you find the comparison you sent me? Are there other pages as helpful?
From this there is absolutely no doubt that the ID you make is correct.
Lat/Lng: 42.5353, 2.8574