LIONEPHA CASTA (CASEY, 1918)

(FIGS 2A, 16A, B, 12A, B, 14D, 18, 22)

Bembidion castum Casey, 1918: 20. Lectotype ♂, designated by Lindroth (1975), in USNM (type # 36818), examined. Type locality: Santa Cruz Mountains, Santa Clara County, California.

Bembidion serenum Casey, 1918: 21. Lectotype ♀, designated by Lindroth (1975), in USNM (type # 36819), examined. Type locality: Arcata, Humboldt Country, California. Synonymy established by Lindroth (1963).

Bembidion brumale Casey, 1918: 22. Lectotype ♀, designated by Lindroth (1975), in USNM (type # 36823, specimen USNMENT01114819), examined (including genitalia and DNA). Synonymy established by Erwin & Kavanaugh (1981: 52), confirmed through DNA sequences. Type locality: Metlakatla, British Columbia. GenBank accession numbers for DNA sequences of the lectotype are MN402439, MN402246 and MN401772; accession number of sequence reads in NCBI’s Sequence Read Archive is SRR5230408.

Bembidion vacivum Casey, 1918: 22. Lectotype ♀, designated by Lindroth (1975), in USNM (type # 36822), examined. Type locality: Skeena River at Terrace, British Columbia. Synonymy established, under the name B. brumale Casey, by Lindroth (1963: 262).

Bembidion nescium Casey, 1918: 30. Lectotype ♂, designated by Lindroth (1975), in USNM (type # 36845), examined. Type locality: Metlakatla, British Columbia. Synonymy established by Lindroth (1963).

Diagnosis: Specimens of this species have relatively pale tibiae, with evident, transverse microsculpture on the elytra; the elytral striae are less impressed, with the fourth stria much less impressed than the first. Sclerite CH 1 as in Figure 14D. Females share with L. kavanaughi a dorsal microtrichial patch of the bursa that is rectangular (not narrowed anteriorly) and with deep, longitudinal, parallel folds (Fig. 9C).

This species is similar in appearance and genitalia to Lionepha kavanaughi, which with it shares pale tibiae, although the femora of L.casta are on average paler than in L. kavanaughi. However, L. casta has less impressed elytral striae. The most definitive characteristic of the male genitalia is the presence of distinct, triangular scales on the left-most membrane of the internal sac (Fig. 18); in contrast, there are no scales on membranes between sclerite CH 1 and the outer, left wall of the aedeagus in L. kavanaughi or L. lindrothi. They are also geographically disjunct, with L. casta occurring only in the Cascades and westward (Fig. 22), and L. kavanaughi being found only in the north-east corner of Oregon and adjacent Washington east to Montana and Wyoming. From the sympatric L. probata it is most easily distinguished by the narrower prothorax, paler legs and sculpticells that are clearly transverse.

Additional characteristics: Body length 3.45–4.22 mm. Antenna piceous. Femora rufous or rufopiceous; tibiae rufous or dark testaceous. Hind wings full-sized in most specimens, although a few brachypterous individuals are known (Erwin & Kavanaugh, 1981). Chromosomes of male 24 + X (Table 5).

Geographic variation: At the easternmost edge of the known range of this species (e.g. from Taneum Creek Campground in Wenatchee National Forest, Washington) specimens are unusually large and dark.

Distribution: One of the more widespread Lionepha, from coastal California north to southern Alaska (Fig. 22). It has not been found east of the Cascades. We agree with Erwin & Kavanaugh (1981) that Lindroth’s (1963) record from Barkerville, BC, is doubtful. A lower elevation species, found between 0 and 1515 m, with the majority of specimens from below 200 m. It has been collected from March through November, with most specimens having been found in the summer.

Habitat: In numerous microhabitats often near water: on the sand or gravel shores of creeks in forests; in marshy areas along creeks in mountain forests. They can also be found during springtime in damp areas in high-elevation grasslands far from water.