Atheta (Datomicra) semidentiventris Lee & Ahn, sp. nov.

(Figs 1 G, 5A–F, 6A–H, 7A–H)

Description. Length 2.0– 2.3 mm. Body (Fig. 1 G) subparallel-sided; surface fairly glossy, densely pubescent with relatively fine punctures. Body dark brown to black; antenna and legs paler. Head. Subquadrate (Fig. 6 A), about as wide as long, widest across eyes, slightly narrower than pronotum; eyes large and prominent, about 1.4–1.5 times as long as temples; gular sutures moderately separated, more or less diverged basally; infraorbital carina complete; cervical carina complete. Antennae (Fig. 6 B) long and slender; antennomeres 1–3 elongate, 1 longest, 4–10 subquadrate to slightly transverse, 11 longer than wide, about as long as preceding two combined. Mouthparts. Labrum (Fig. 5 A) transverse, slightly emarginate in anterior margin, with ε-sensillum and eight macrosetae on each side of midline; epipharynx (Fig. 5 B) with several sensilla, including two lateral sensory rows on each side of midline; α-sensillum long and setaceous, more than 2.0 times as long as ε-sensillum; β-sensillum reduced; γsensillum very short. Mandibles (Figs 5 C–D) asymmetrical, subtriangular, decurved and pointed apically, about 1.5–1.6 times as long as basal width; few denticles present in molar region; right one (Fig. 5 C) with small internal tooth, internal margin slightly serrulate; prostheca developed, composed of three portions. Galea and lacinia of maxilla (Fig 5 E) moderately long and slender; lacinia composed of seven spines in distal comb region, two isolated spines present; maxillary palpus elongate and pubescent; palpomere 1 smallest, 2 about 2.5–2.7 times as long as wide, 3 slightly longer than 2, about 2.3–2.5 times as long as wide, 4 digitiform, filamentous sensilla reaching to basal half. Labium (Fig. 5 F) with ligula relatively slender, divided into two lobes in basal half; prementum with two medial setae narrowly separated; two basal pores absent; several medial pseudopores, lateral pseudopores, one setal pore and two real pores present on each side of midline; labial palpus elongate, with many setulae; palpomere 1 largest, about 1.4–1.6 times as long as wide, γ-setula contiguous with b-seta, 2 shortest, about 1.3–1.5 times as long as wide, 3 more or less dilated apically and about as long as 1, about 2.5–3.0 times as long as wide. Mentum (Fig. 5 F) trapezoidal, anterior margin emarginate; v-seta relatively long, close to u-seta. Thorax. Pronotum (Fig. 6 C) approximately 1.3 times as wide as long, widest at middle; hypomera fully visible in lateral aspect. Metanotal scutum (Fig. 6 E) with one long seta and about three or four short setae on each side of midline. Mesocoxal cavities narrowly separated; mesoventral process (Fig. 6 F) slightly pointed at apex, slightly longer than isthmus and metaventral process combined; length ratio of mesoventral process, isthmus and metaventral process 12:6:4. Elytra slightly longer and wider than pronotum; elytron (Fig. 6 H) approximately 1.6 times as long as wide, pubescence directed posteriorly and postero-laterally; postero-lateral margin almost straight; hind wings fully developed, flabellum (Fig. 6 E) composed of about four or five setose lobes. Legs. Slender and long, with dense pubescence and macrosetae; meso- and metatibiae with different length of two spurs at apex; tarsal formula 4-5-5, length ratio of tarsomeres 23:24:26:60 (protarsus); 28:31:32:30:58 (mesotarsus); 33:34:35:36:95 (metatarsus); one empodial seta present, shorter than claw. Abdomen. Parallel-sided, convergent at apex; surface distinctly glossy and densely pubescent, with reticulate microsculpture; macrochaetal arrangement of tergites II–VI 02-13 (or 23)-23-23-23; male tergite VIII (Fig. 7 A) with five macrosetae on each side of midline, posterior margin truncate, slightly crenate; male sternite VIII (Fig. 7 B) with about eight macrosetae on each side of midline, posterior margin convex, slightly rounded, with inconspicuous marginal setae; female tergite VIII (Fig. 7 C) with five macrosetae on each side of midline, posterior margin subtruncate; female sternite VIII (Fig. 7 D) with seven macrosetae on each side of midline, posterior margin rounded, with slightly conspicuous marginal setae, minute setae present in median region. Aedeagus. Median lobe (Figs 7 E–F) ovate, apical process narrow apically in ventral aspect. Apical lobe of paramerites (Fig. 7 G) subparallel-sided, with four setae very short; a-, b- and c-seta subequal in length and slightly longer than d-seta. Spermatheca. Bursa elongate, with umbilicus; duct relatively long and recurved, round at apex (Fig. 7 H).

Type material. Holotype, ♂, labeled as follows: ‘ Gyeonggi Prov., Seoul-si, Seongbuk-gu, Dongseon-dong, 24 v 1988, GS Jang’ ; Paratypes, 4 exx. (total): 1♂. , same data as Holotype except for ‘ 27 x 1985, GS Jang’; 1♂ 2♀♀, Seoul-si, Seocho-gu, Wonji-dong, 1 vi 1985, GS Jang.

Distribution. Korea (South).

Remarks. Atheta (Datomicra) semidentiventris is very similar to A. (D.) dentiventris, but can be distinguished by the characters provided in the key and different shape and structure of aedeagus and spermatheca. The macrochaetal arrangement of abdominal tergite III of this species differs from that of the subgenus Datomicra, but this character is not sufficient to separate them as a different subgenus of Atheta . Apart from that most morphological characters are accordant with other Atheta (Datomicra) species. Therefore, the taxonomic position of this species is tentatively placed in this subgenus, pending further comprehensive research of the species. All specimens were collected with A. (D.) dentiventris .

Etymology. Named from Latin semi meaning "half", which refers to similarity with the species A. (A.) dentiventris .