Spotting

If it really belongs to the genus Phthiacnemia, than it should be Phthiacnemia picta - because that's the only species within this genus. Its distribution area covers Costa Rica.

Yes, actually I got to Phthiacnemia because it was the only genus without metallic iridescense on the surface of the body and the humeral angle. But I agree with you, it is better to leave it at the complex.

Sorry, I didn't want to type a question mark, but an exclamation mark.

Hi Ignacio,
a full pronotum is needed to try an ID? I guess - at the moment - it's better to stay with the complex...

Hi,Torsten
What do you think about Phthiacnemia?
It seems to fit using the Brailovsky key (2009) but you're right, more angles are needed. Pronotum and abdomen would be useful, but this is the only photo I have. If I found one again, I'll be sure to get those angles, too.

Hi Ignacio,
the bug belongs to the Phthia complex. Unfortunately, a more specific ID isn't possible having just that photo :-(.