Aquatic hemipterans of the family Pleidae (Hemiptera: Heteroptera: Nepomorpha) represent a not very well explored group of water insect. Pleidae (Pygmy backswimmers) are tiny (1 ? 3 mm) hemipterans living mostly on the submerged vegetation of lentic water systems. The family is cosmopolitan, but the only species we can find in the Czech Republic is Plea minutissima, which is the most researched one(together with Neoplea striola). This family consists of 33 valid species divided into four generas ? Plea Leach, 1817, Neoplea Esaki a China, 1928, Paraplea Esaki a China, 1928 and Heteroplea Cook, 2011 according to the recent status of knowledge. This thesis is the very first attempt to create a complete catalogue of species in this family. It deals with a list of species, species distribution and key to the genera and species of Pleidae. The list of literature represents bibliography of family.