New taxonomic data are provided on the ladybird spider genus Eresus Walckenaer, 1805 in Turkey and Iran. Eresus adaleari Zamani & Szűts, sp. n. is described as a new species, on the basis of a single male specimen collected in Semnan Province, northeastern Iran, and Eresus lavrosiae Mcheidze, 1997, previously known solely from the original description of the male holotype from Georgia, is re-described on the basis of one newly collected male specimen from Kars Province, eastern Turkey. Both of these species are generally dark-colored, which contrasts with the usual coloration of males of this genus. Finally, a few methods and suggestions that might accelerate and improve taxonomic procedures for studying this group are discussed.