1♂, Miomote, alt. 276 m, on the right bank of Miomotegawa River, Murakami-shi, Niigata Prefecture, Japan (38.273211°N, 139.779922°E), 12.vi.–17.vii.2021, Hirotarô Itô leg., in the collection of HI.

Figure 2. 

Pterostichus asahinus male from Miomote, on the right bank of the Miomotegawa River A habitus dorsal view B–E Endophallus left lateral (B) ventral (C) right lateral (D) and dorsal (E) views F–H right paramere left lateral (F) apical (G) and dorsal (H) views. go, gonopore; lal, left apical lobe; lpl, left preapical lobe; rpl, right preapical lobe.

Sasakawa et al. (2020) suggested that P. asahinus and P. falcispinus might be conspecific. However, this hypothesis remained untested because males from the type locality of P. asahinus have not been examined. The male specimen examined here was obtained from a valley southwest of Mt. Dôrokujinpô, which can virtually be regarded as the type locality (Fig. 1). The structures of the endophallus and right paramere of this specimen are identical to those of the eastern type of P. falcispinus in Sasakawa et al. (2020). Its body length is intermediate between that of the eastern and western types of P. falcispinus as follows: body length from mandible apices to elytral end (BLm) 16.32 mm, that from anterior margin of labrum (BLl) 14.72 mm, and that from clypeal apex (BLc) 14.26 mm. Based on these results, we regard P. asahinus and P. falcispinus as conspecific. The results of the discriminant analysis support this conclusion. The P. asahinus holotype was classified in this newly defined P. asahinus in the discriminant function analysis, and was within the area of P. asahinus on the scatterplot of the first two canonical variates (Fig. 3).

Figure 3. 

Scatterplot of the first two canonical variates obtained from the discriminant analysis of four measurements of the female pronotum.

Holotype : ♀, Mt. Koshibayama, alt. 235 m, Awashima Island, Awashimaura-mura, Niigata Prefecture, Japan, 24.v.–14.vi.2015, Hirotarô Itô leg., deposited in the Laboratory of Zoology, Department of Science Education, Faculty of Education, Chiba University, Chiba, Japan.

In the discriminant function analysis, the Awashima specimen was classified as P. yahikosanus. On the scatterplots of the first two canonical variates, the specimen was located outside of, but close to, the area of P. yahikosanus (Fig. 3). These results suggest that the Awashima specimen is most similar in external morphology to, but different from, P. yahikosanus. Differences between the Awashima specimen and P. yahikosanus were also observed in other morphological features: the body length of the Awashima specimen (see below) is smaller than that of P. yahikosanus (n=6 from Mt. Yahikosan; BLm 15.32–14.35, mean 14.94 mm; BLl 14.22–13.46, mean 13.73 mm; BLc 13.64–12.89, mean 13.18 mm) (Fig. 4A, B); in the pronotum, anterior angles are barely produced, hind angles are obtuse, and posterior margin is arcuate posteriorly behind the laterobasal impressions in the Awashima specimen (Fig. 4C), whereas in P. yahikosanus, anterior angles are notably produced, hind angles are right-angled to acute, and the posterior margin behind the laterobasal impressions is almost straight (Fig. 4D); the body of the Awashima specimen is darker than that of P. yahikosanus (Fig. 4A–D); and pigmentation on the innermost part of vagina is smaller in the Awashima specimen, less than half the size of median and seminal apophyses (Fig. 4E), while it is larger than these apophyses in P. yahikosanus (Fig. 4F). In the macrogenys species group, pronotum shape and the pigmentation on the innermost part of vagina differ distinctly among species and are used as important species-level diagnostic characters (e.g., Sasakawa 2005; Sugimura 2005; Morita et al. 2013). Because these characters differ distinctly between the Awashima specimen and P. yahikosanus, we describe the Awashima specimen as a new species. Based on information on the morphological features of the pronotum and female genitalia in related species (Sasakawa et al. 2020 and references therein), notably produced pronotal anterior angles and developed vaginal pigmentation are limited to some species and considered to be derived character states in the macrogenys species group. Therefore, the Awashima species is considered more ancestral than P. yahikosanus with respect to the pronotal and genital features.

Figure 4. 

Pterostichus awashimaensis sp. nov. holotype female (A, C, E) and P. yahikosanus female from Mt. Yahikosan (B, D, F) A, B habitus dorsal view C, D pronotum dorsal view E, F vagina anterior view. am, apophysis of the median oviduct; as, apophysis of the seminal canal; m, median oviduct; p, pigmentation on the innermost part of the vagina; sp, spermatheca.

BLm 13.79 mm; BLl 12.66 mm; BLc 12.13 mm. Head, pronotum, and elytra dark brown; appendages reddish brown. Dorsal surface almost smooth except for laterobasal impressions of the pronotum, the anterior half of which bear several transverse wrinkles and the posterior half of which are weakly punctate.

Head large, widest at tempora, which are distinctly swollen; width at the widest point larger than pronotal posterior margin width; length from clypeal apex to neck base longer than pronotum length along the median line. Left mandible larger than the right and curved at the apical 1/4; length between mandible apex and posterolateral end on dorsal side slightly shorter than 2.5 times the anterior width of the clypeus. Eyes weakly convex, with the anterior-posterior length longer than 1/2 length of antennal segment 1. Antennal segment 2 with two setae.

Pronotum cordate, notably flat, widest at apical 1/5. Lateral margins arcuate on apical 2/3, slightly sinuate on basal 1/3; two marginal setae on each lateral side, anterior setae near widest pronotal point, and posterior setae near hind angles. Anterior margin emarginated, with curvature approximately the same as that of apical 2/3 of lateral margins; anterior angles widely rounded and barely produced. Hind angles obtuse. Posterior margin only slightly emarginated at median area, weakly but distinctly arcuate posteriorly behind the laterobasal impressions. Median line impressed in the middle, not reaching either the anterior or posterior margins; laterobasal impressions single, shallow.

Elytra sides almost parallel, less convex; shoulder distinct, but not denticulate; apices rounded; scutellar stria present, connected to stria 1 on the right side but not on the left; 1 setigerous puncture on stria 1 at the level of the posterior end of scutellum; two setigerous punctures on interval 3, anterior one slightly before the middle and posterior one on apical 1/5, both adjoining stria 2. Hind wings completely atrophied. First fore tarsomere no adhesive hairs on ventral side.

Female genital structures identical to those of other consubgeners; apophyses of seminal canal and median oviduct fully sclerotized; pigmentation on the innermost part of the vagina present, but less than half the size of apophyses of seminal canal and median oviduct; other parts of vagina lack conspicuous pigmentation.