Ilybius wasastjernae (SAHLBERG, 1824) in Poland – a relict species of Dytiscidae (Coleoptera) with unique habitat preferences. / Ilybius wasastjernae (SAHLBERG, 1824) w Polsce – reliktowy gatunek Dytiscidae (Coleoptera) o unikalnych wymaganiach środowiskowych.

Ilybius wasastjernae is a rarely collected member of a genus displaying unique habitat preferences. To date, there have been four records in Poland, always of single or just a very few individuals. Here, we are report four additional localities where this species was found in recent years; at one of them, more than ten individuals were seen. The southernmost of these localities was in the Świętokrzyskie Mts., far beyond the geographical range of this species in Poland, hitherto assumed to be restricted to the Baltic Coast and the Pomeranian Lake District regions in the northern part of the country. The majority of records come from pools formed in pits where root masses of uprooted trees used to be. Our observations show that the species occurs in small numbers (only a single individual was collected in one pool), and prefers cold, shaded water.