Bembidion breve (Motschulsky, 1845)

Sproul, John S. & Maddison, David R., 2018, Cryptic species in the mountaintops: species delimitation and taxonomy of the Bembidion breve species group (Coleoptera: Carabidae) aided by genomic architecture of a century-old type specimen, Zoological Journal of the Linnean Society 183, pp. 556-583 : 570-571

KEY TO SPECIES OF THE BREVE GROUP

1 Elytra notably convex, with lateral margins strongly rounded, resulting in inflated appearance ( Fig. 2D); striae 3 and 4 partially disappeared or very weak ( Fig. 2D). Pronotum sinuate laterally ( Fig. 11G, see also Fig. 11I). Hindbody dark brown or reddish brown and generally slightly paler than the forebody. Male genitalia with darkened patch of scales apically ( Fig. 9H, see inset) and lacking sclerite ‘St’ ( Figs 9G, H, 10G); 4.6–5.1 mm ................................................................................ B. testatum

– Elytra flat or convex, or with lateral margins somewhat rounded, but not strongly rounded laterally and therefore lacking inflated appearance, striae weak, or not. Pronotum sinuate laterally, or not. Male genitalia lacking darkened patch of scales apically....................................................................................2

2 (1) Pronotum with hind angles near 90° ( Fig. 11D–F, I), or slightly obtuse ( Fig. 11H) .................................3

– Pronotum with hind angles strongly obtuse ( Fig. 11A, B) .........................................................................8

3 (2) Pronotum broad ( Fig. 2A–C), with broad lateral explanation and broad base ( Fig. 11D–F). Body convex, with a stout appearance. Smaller, most specimens less than 4.8 mm (although can be up to 5 mm).....4

– Pronotum broad or not ( Fig. 11H, I). Body convex or somewhat flattened, but greater than 4.8 mm (females> 5.1 mm).......................................................................................................................................7

4 (3) Male genitalia with expanded sclerite ‘St’ as in Figure 10E. Montana, southeastern British Columbia, southwestern Alberta, northeastern Oregon (and likely northern Idaho) ( Fig. 16B); 4–4.5 mm .................................................................................................................................................... B. geopearlis

– Male genitalia with sclerite ‘ St’ as in Figure 10C, D, F. California, Nevada , western and southeastern Oregon, western Washington, western and southeastern British Columbia, north to Alaska ................5

5 (4) Elytra with lateral margins somewhat rounded and narrowed at shoulder, dorsal punctures strongly foveate and striae often pronounced ( Fig. 1C). Pronotum fairly large relative to elytral length, broad lateral explanation generally lacking (specimens from the Sierra Nevada may have a broad lateral explanation). Male genitalia with medium-length flagellum and diamond-shaped sclerite ‘St’ ( Figs 8E, F, 10C). Smaller, 3.7–4.5 mm ............................................................................................................ B. breve

– Elytra fairly parallel-sided, broad at shoulder, often tapering towards apex, dorsal punctures weakly foveate. Male genitalia with apical half narrower and more tapered, third and long, sinuate flagellum ( Fig. 9A, B, E, F)............................................................................................................................................6

6 (5) Male genitalia lacking large arcuate sclerite ‘St’ ( Figs 9A, B, 10D). Sierra Nevada in California, Nevada, southeastern Oregon ( Fig. 16A); 4–4.6 mm ...................................................................... B. saturatum

– Male genitalia with a large, arcuate sclerite ‘St’ ( Figs 9E, F, 10F). Northwestern California, and the Cascades from Oregon to southern British Columbia ( Fig. 16A); 4.1–5.0 mm, most ≤ 4.8 mm ...................................................................................................................................................... B. vulcanix

7 (3) Pronotum narrow and strongly sinuate laterally ( Figs 3, 11I). Legs and antennae elongate and slender. Elytra widest behind middle. Forebody and hind body generally unicolourous black (in rare specimens, elytral disc brown or reddish brown), in some specimens with a bluish hue; 5.2–6 mm ......... B. oromaia

– Pronotum broad (at least as broad as one elytron); in some specimens, slightly sinuate laterally ( Figs 1D, 11H). Legs and antennae less elongate and slender. Elytra more or less parallel-sided, widest near middle and generally tapering towards apex. Elytral microsculpture often granulate in females ( Fig. 13F). Forebody and hindbody unicolourous dark brown (occasionally black) with aeneous hue. Male genitalia not bent basally, flagellum short and weakly sinuate; 4.9–5.6 mm ........................... B. laxatum

8 (2) Male genitalia as in Figures 8C, D and 10B. Elytral dorsal punctures weakly foveate (especially in specimens from California and Oregon) ( Fig. 1B). Pronotum relatively flat with a broad lateral explanation ( Fig. 11B), weak laterobasal carina and shallow basal fovea ( Fig. 12C); 4.0– 5.3 mm, most ≥ 4.5 mm .................................................................................................................................................. B. ampliatum

– Elytral dorsal punctures strongly foveate ( Fig. 1A, C). Pronotum with strong laterobasal carina, basal fovea somewhat deeper with less broad lateral explanation ( Figs 11A, G, 12A). .........................................................................................................................................................9

9 (8) Body parallel-sided and relatively flat ( Fig. 1A). Male genitalia as in Figures 8A, B and 10A; 3.7–4.9 mm, most ≥ 4.1 mm ....................................................................................................... B. lividulum

– Pronotum and elytra quite convex. Elytra with somewhat rounded lateral margin ( Fig. 1C). Male genitalia as in Figures 8E, F and 10C. Smaller, 3.7–4.5 mm .......................................................... B. breve