Bembidion testatum, CASEY, 1918

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 : 579-580

BEMBIDION TESTATUM CASEY

( FIGS 2D, 9G, H, 10G, 11G, 17A)

Bembidion testatum Casey, 1918: 30 . Lectotype male, designated by Erwin (1984: 174), in USNM, labelled ‘Ca[a vertical line crossed by two shorter horizontal lines]’ [white paper], (male symbol) [hand drawn on white paper], ‘CASEY bequest 1925’ [white paper], ‘TYPE USNM 36842’ [red paper], ‘ LECTOTYPE [male symbol] Bembidion testatum Csy. By Erwin ‘77’ [white paper, partly handwritten]. Examined. Type locality: Lake Tahoe, California.

Nomenclatural notes: This is the species referred to as ‘ Bembidion “Lily Lake Creek”’ in Sproul & Maddison (2017).

Diagnosis: This fairly large-bodied species is most easily recognized by the inflated appearance of the elytra and narrow pronotum relative to width of the elytra ( Fig. 2D). Forebody dark brown or black; hind body from dark brown to reddish brown, often paler than forebody. Pronotum narrow relative to the width of the elytra; strongly sinuate laterally ( Figs 2D, 11G); hind angles near 90° with basal fovea deeply excavated ( Fig. 11G). Elytra notably convex with strongly rounded lateral margin resulting in an inflated appearance; dorsal punctures weakly foveate, elytral striae weak with striae three and four partially disappeared in some specimens. Microsculpture strongly etched in females and moderately etched in males. Male genitalia with darkened patch of membranes apically; sclerite ‘St’ lacking; flagellum sinuate and moderately long; ostial flag with an abbreviated sinuation not nearing the ventral surface of the aedeagus, and not extending far anteriorly ( Figs 9G, H, 10G).

Comparison with similar species: Can be confused with B. saturatum and B. breve in the northern Sierra Nevada. Distinguished from both by a larger body size, more convex elytra, and a darkened patch of scale-like structures apically in the male genitalia (see inset in Fig. 9H). Further distinguished from the former by having a narrower pronotum at the base. Distinguished from the latter by having very weakly foveate dorsal punctures and weak striae of the elytra.

Geographic distribution: Known from the Sierra Nevada and Trinity Alps in California, as well as a single locality in southern Oregon ( Fig. 17A).

Habitat: Appears to be restricted to small, subalpine creeks.

Geographic variation: Some specimens from the Trinity Alps in northwestern California have a slightly longer flagellum in male genitalia. The single individual we sampled from Mount Ashland , Oregon has four distinctive bases in 28S (three of which are ambiguities in DNA4173, but non-ambiguous and different in all other specimens), but is not notably distinct in the other genes. The Oregon specimen also has less sinuate later margins of the pronotum than typical California specimens .