Identification key to the species of the subgenus Mesolethrus

1 Dorsal surface of mandibles in both sexes with elevated sharp keels (Figs. 1–2). Elytra usually with definitely impressed striae (Figs. 1–2). Ventrites 1–5 with prominent central denticle posteriorly (Fig. 39) (rarely denticles indistinct). Parameres straight, apically narrowly rounded (Figs. 9–10). Sclerotized apex of endophallus elongate, subclavate, in lateral view curved, in dorsal view anteriorly trilobed, surface sharply spiny-granular (Figs. 22–23). Dorsal body surface shiny (Figs. 1–2) (except older and abraded specimens)................................................................. L. inermis Reitter, 1897

- Dorsal surface of mandibles in both sexes with low and obtuse keels (Figs. 3–8, 38, 45). Elytral striae superficial (Figs. 3–4, 6–8) or moderately impressed (Fig. 5), but not definitely impressed. Ventrites without denticles (Figs. 40–43). Parameres curved anteriorly (Figs. 11–21). Sclerotized apex of endophallus resembles a subrectangular plate or elongate, not subclavate, not curved in lateral view, anteriorly bilobed or suboval, surface not sharply granular (Figs. 24–31). Dorsal body surface with faint metallic tinge (Figs. 3–4, 6–8) (except older and abraded specimens with black surface), or if metallic tinge pronounced (Figs. 5, 45)—surface usually more or less dim.............................................................. 2

2 Parameres in lateral view apically acuminate (Figs. 11–14). Sclerotized apex of endophallus elongate, anteriorly rounded or spine-like prominent (Figs. 24–27). Gena about 1.5 times as large as eye width, nearly rectangular: laterally widely truncate, anterolateral and posterolateral angles nearly right angles (Figs. 33–34).......................................... 3 - Parameres in lateral view apically roundish (Figs. 15–21). Sclerotized apex of endophallus resembles a subrectangular plate, anteriorly bilobed (Figs. 28–31). Gena with various widths, but laterally rounded or narrowly and obliquely truncate, anterolateral angle usually rounded, posterolateral angle obtuse (Figs. 35–37)..................................... 4

3 Sclerotized apex of endophallus wider at the base, in dorsal view suboval, anteriorly with prominent spine (Fig. 24). Parameres narrower, sinuous along the inner edge (Figs. 11–12). Punctation of head and pronotum comparatively fine. Dorsal surface of body with faint bronze tinge or black (Fig. 3).................................... L. shakhristanicus Nikolajev, 2003

- Sclerotized apex of endophallus narrow at the base, in dorsal view distinctly elongated, anteriorly rounded (Figs. 25–27). Parameres distinctly wider, near straight along inner edge (Figs. 13–14). Punctation of head and pronotum comparatively coarse. Dorsal surface of body with faint blue tinge or black (Fig. 4)..................... L. nuratavicus Nikolajev, 1987

4 Sclerotized apex of endophallus in dorsal view with lobes distinctly shorter than basal part of sclerite (Fig. 30). Parameres comparatively wider, apically not widened and relatively weakly curved inwardly (Figs. 19–21). Punctation of elytra double (sparse points and smaller dense points), striae superficial. Punctation of pronotum coarse (Figs. 7–8). Gena 2.5–3.1 times as large as eye width (Fig. 37). Body length 15–17.4 mm ............... L. dyonini A. Shapovalov & Bagaturov, new species

- Sclerotized apex of endophallus in dorsal view with lobes about as long as or only weakly shorter than basal part of sclerite (Figs. 28–29). Parameres comparatively narrower (Figs. 15–18). Elytra finely shagreened, with fine simple punctation (Figs. 5–6). If punctation of pronotum coarse, then punctures comparatively larger and elytra usually with distinct striae and convex interstriae (Fig. 5)..................................................................................... 5

5 Parameres curved inwardly and usually slightly widened apically (Figs. 15–16). Sclerotized apex of endophallus laterally subparallel–sided (Fig. 28). Gena usually 1.8–2.0 times as large as eye width (Fig. 35); rarely, in specimens from Hissar Range, gena can be up to 2.4–2.5 times as large as eye width. Punctation of head and pronotum rather coarse, elytral striae usually distinct and partly impressed with convex intervals (Figs. 5, 45) (except specimens from Hissar with superficial striae). Dorsal body surface usually with pronounced metallic tinge (Figs. 5, 45). Comparatively smaller species with body length 9–16 mm ............................................................................. L. microbuccis Ballion, 1871

- Parameres comparatively weakly curved inwardly and not widened apically (Figs. 17–18). Sclerotized apex of endophallus usually arcuate laterally (Figs. 29). Gena 2.1–2.8 times as large as eye width (Figs. 36). Punctation of head and pronotum usually finer, elytral striae thin and superficial with flattened interstriae (Fig. 6). Dorsal body surface with faint metallic tinge (Fig. 6). Body length 14–19 mm ...................................................... L. elisae Nikolajev, 2001