Cladotanytarsus molestus Hirvenoja, 1962 in Poland: toward the identification of bioindicative Tanytarsini (Diptera: Chironomidae)

A rare chironomid species, Cladotanytarsus molestus Hirvenoja, 1962, collected at Lake Straszyńskie (the drinking water reservoir for the city of Gdańsk), was recorded from Poland for the first time. The adult male of the species is redescribed, and intraspecific morphological variations of diagnostic structures are presented in detail. Data on the species’ biology are also provided.