FIG. 1.

Geographic origin of the infected wild rodents (localities indicated by arrows) and the geographical distribution of (i) L. lemmus and L. sibiricus western type (found west of the Lena River) (ii) L. sibiricus central type (found between the Lena and Kolyma Rivers), and (iii) L. sibiricus eastern type (or L. trimucronatus, found east of the Kolyma River) (8, 10). Localities from which lemming samples were analyzed are shown by dots. In addition, Finse, Norway, (origin of the lemming colony), and Salla, Finland (the site of a putative lemming-borne outbreak in 1942), are indicated.