Hi Vasiliy and Bernd
I compared all my Samos pictures of Polyploca korbi and those in ESPERIANA 13 with Bernds Polyploca: for me it is definitely not Polyploca korbi. Hard to explain why, of course. The lines on Bernds photos are much too "wild", korbi has a quite simple and clear structure of lines and coloring. And, of course the distribution of korbi does not fit at all to the place where Bernd has found it (next place for korbi in Europe is Samos Island GR). ok. this is a very weak argument.
So: my opinion is: this is Polypolca ridens. korbi should be accepted only if the specimen can be dissected and korbi can be confirmed (genitals in ESPERIANA 13).