This article presents a species new to science called Phthiracarus paraferrugineus sp. nov., which was recorded in the nature reserve Cisy Staropolskie im. Leona Wyczółkowskiego in Wierzchlas. The authors also give information about new sites of occurrence and comments about the morphology of some species rarely found in Poland—Paratritia baloghi Moritz, 1966 (second record in Poland) and Euphthiracarus reticulatus (Berlese, 1913)—as well as several more common species (Phthiracarus bryobius Jacot, 1930, Phthiracarus clavatus Parry, 1979, Phthiracarus compressus Jacot, 1930, Phthiracarus longulus C.L. Koch, 1841, Phthiracarus nitens Nicolet, 1855). The article also contains a description of a previously unknown developmental stage—the tritonymph of Acrotritia duplicata (Grandjejan, 1953).