Elaphrus sp. marsh ground beetle (Carabidae)

What were yesterday’s psychedelic speckles?

They were elytral ornaments of the magical mystery Elaphrus, a ground beetle that spends its time lurking about the edges of waterways looking suspiciously like a miniature tiger beetle even though it isn’t.

So:

Eight points to Ben Coulter who guessed the genus almost before I posted the challenge. Two points to B. Boudinot for not overthinking the question and stating that the underlying structure was the elytron.  Plus, one point to Ainsley- who incidentally is the world’s premiere expert on beetle refractive coloration- for providing the mechanical explanation.

There’s been some chatter that I ought to keep the comments hidden until the answer is revealed. I don’t feel strongly one way or the other. Concealed comments would certainly foster greater participation. But I also enjoy the conditional strategies that emerge as people hedge that the earlier guesses might be incorrect.

If we adopt a new Mystery policy, it won’t go into effect until next month. What do you think?