Laelaps ekstremi Zakhvatkin, 1948: 71, figs 6, 10, 18, 20, 21.
Laelaps ekstremi. — Lange, 1955: 334, figs 686, 687; Strandtmann & Wharton, 1958: 61; Costa, 1961: 40, figs 66–69; Mašán & Fenďa, 2010: 36.
Laelaps extremi. — Mrciak, 1964: 166; Senotrusova, 1987: 167, fig. 82; Goncharova et al., 1991: 34.
Laelaps jettmari. — Bregetova, 1956: 108, 114, figs 198, 214, 224– 227 (partim); Tipton, 1960: 271 (partim); Goncharova & Buyakova, 1964: 381, fig. 3, 1 (partim).
Type locality. Russia, Volgograd Region, Kotelnikov District.
Type host. Microtus arvalis (Pallas, 1778).
Principal hosts. Voles of the genus Microtus (according to Zakhvatkin, 1948).
Distribution. Europe, Northern and Central Asia eastward to the Russian Far East, China and Japan (Zakhvatkin, 1948; Goncharova et al., 1991). In Siberia, it has been recorded from Transbaikalia (Goncharova et al., 1991).
Remarks. Zakhvatkin (1948) acknowledged that his species (L. ekstremi) is very similar to L. jettmari Vitzthum, 1930 from Manchuria. Bregerova (1956) synonymised the two species, but Costa (1961) rejected this synonymy and reestabished L. ekstremi as a valid species (see also Mrciak, 1964).