Notes on the identification of the pseudoscorpions Chthonius tetrachelatusand C. kewi (Pseudoscorpiones: Chthoniidae)

In pseudoscorpions identification to the species level can be difficult. In some genera, such as in Chthonius, chaetotaxy is a necessary tool to be able the differentiate between closely related species. The key characters to separate the closely related Chthonius tetrachelatus and C. kewi which were used until now turn out to be incorrect. In this paper new characters are proposed. Study of this group revealed that C. kewi, originally described from Britain, is probably not present in the Netherlands. Material identified previously as C. kewi, proved to belong to C. tetrachelatus. In this contribution an update of the key to the pseudoscorpion species of the Netherlands is presented. The total number of Dutch species is now 22.