I was going through my Heteroptera photo folder earlier today and realized that majority of what I've photographed this year are from families Lygaeidae and Miridae, and this T. arenarius was no different, until I noticed that it has been moved from the family Lygaeidae to family Rhyparochromidae, commonly known as the Dirt-colored Seed Bugs.
Of the three species in genus Trapezonotus, this one is really easy to confuse to one of them, T. desertus. And that's where the last photo in the album comes in. From what I managed to find out, almost always, this T. arenarius has the inner dotted line broken, that I pointed in the last photo, on either or both sides of the scutellum (=the black upside-down triangle).
Although that dotted line is not always broken with T. arenarius, it is never broken with T. desertus. Other than that, it requires an examination of the male parameres (=part if the external reproductive organs of the male insects) to tell the difference between the two species if you find one of these insects and it has an unbroken dotted line and you want to be sure of the species, if both are known to be found in same area.
Although trying to see the dotted line while outside photographing these tiny bugs, can be quite hard, as they are really mobile, fast and quite small. This species being only 4-4.5 mm (0.15-0.17 in) in body length.
I got bit lucky with this individual for finding it posing on that piece of lichen on a rock and it didn't seem to mind me moving around it, until my 4th shot when I lost my balance in awkward angle and almost fell on it 😬😁. I had been trying to photograph these fast buggers previously for few different days, so was happy to at least get these decent shots of it.
Found from the northern parts of Europe, North America, Asia, Russia, from open, dry, sandy soil (coastal and land dunes) and rocky areas.
Oh and this is not a nymph, this and the other Trapezonotus adults have either long or short wings, like this one.