Potamophilus kelabitensis sp. nov., a new riffle beetle (Coleoptera, Elmidae) discovered in the Kelabit Highlands (northern Sarawak) and Sapulut environment (southern Sabah), is described. Illustrations of the habitus and diagnostic characters of the new species are presented. Differences from the type species P. acuminatus (Fabricius, 1792) from the Palaearctic region, based on DNA barcodes and morphological characters, are discussed. Selected morphological characters of all known species of Potamophilus from Vietnam, Myanmar, and Papua New Guinea are also compared with the new species. The systematic position of the genus relative to other sympatric genera of the subfamilies Larainae LeConte, 1861 and selected Elminae Curtis, 1830 belonging to three tribes is discussed based on phylogenetic trees inferred from the mitochondrial COI and nuclear ArgK as well as 18S rRNA gene sequences.

We recorded three mite species, Pergamasus (Thenargamasus) instatutus Athias-Henriot, 1967, Pergamasus (Pergamasus) laminarius Witaliński, 1971 and Holoparasitus ampullaris Witaliński, 1994, from Slovakia for the first time. Mites of the genera Pergamasus Berlese, 1903 and Holoparasitus Oudemans, 1936 are predatory mites living mainly in a soil and a rotting organic matter of the Holarctic region with a centre of distribution in Europe. Till now, P. instatutus was recorded in Austria and Hungary, while P. laminarius and H. ampullaris were known only from Poland.

Poecilochirus necrophori Vitzthum, 1930 is a Palearctic distributed species, which deutonymphs are phoretic on some burying beetles (Coleoptera: Silphidae). The mites use adult beetles for transport to carcasses where the deutonymphs moult into adults and both mites and beetles feed and reproduce. A life cycle of Poecilochirus species is synchronized with their phoronts and they can be used in a forensic acarology as indicators of post mortem interval. We present the first record of P. necrophori from Turkey. Phoretic deutonymphs of P. necrophori were found on the beetle Nicrophorus vespillo (L.) (Coleoptera: Silphidae) in Sakarya province. The deutonymphs were also found on carcasses of marten (Marten sp.) and mole (Talpa sp.) from Sakarya, Turkey. Moreover, a significance of Poecilochirus species in forensic acarology is briefly discussed.

Hydraena schuleri Ganglbauer, 1901 was rediscovered after 18 years in Starý Potok, a small stream in eastern Slovakia, and we recorded it, for the first time, from the small rivers Stará Rieka and Udava in southern and eastern Slovakia. Adults were collected mainly from submerged moss growing on rocks in shallow water, where they were found together with Hydraena minutissima Stephens, 1929, H. pulchella Germar, 1824, H. pygmaea Waterhouse, 1833; Ochthebius colveranus Ferro, 1979, O. melanescens Dalla Torre, 1877, and O. metallescens Rosenhauer, 1847. We provide illustrations of the habitus and aedeagus, and a distribution map.