(Updated and revised from Ahn, 1996; Song et al., 2018; Yoo and Ahn, 2021. Note that dissections of the male genitalia are essential for correct species identification.)
1. Body black, rarely dark reddish brown.................................................................... 2
– Body brown to reddish brown........................................................................... 7
2. Hypomeron without longitudinal carina, more angulated posteriorly; mentum with deeper anterior emargination; median lobe (fig. 36 in Ahn, 1996)......................................................................... D. pacifica
– Hypomeron with longitudinal carina, less angulated posteriorly; mentum with shallower anterior emargiantion........... 3
3. Elytron wider than long; posterior margin of male sternite VIII crenate; median lobe (fig. 26 in Ahn, 1996).... D. fulviventris
– Elytron longer than wide; posterior margin of male sternite VIII smooth.......................................... 4
4. Anterior margin of labrum not truncated; median lobe (fig. 7 in Ahn, 1996); distributed in the NE Pacific coasts.................................................................................................... D. densissima
– Anterior margin of labrum truncated; distributed in the NW Pacific coats and Alaska................................ 5
5. Pronotum and elytra without distinctively long filiform setae; mandible not pointed; median lobe (fig. 22 in Ahn, 1996)............................................................................................... D. alaskana
– Pronotum and elytra with distinctively long filiform setae; mandible more or less pointed........................... 6
6. Median lobe (fig. 21 in Ahn, 1996); distributed in Korea and Honshu (Japan)................................ D. aokii
– Median lobe (figs. 3–4 in Song et al., 2018); distributed in Hokkaido (Japan), Kamchatka (Russia), and USA (Alaska)............................................................................................. D. hokkaidona
7. Labrum large and robust; mandible more elongate; labial palpi with 3 distinct articles; ligula with 2 minute setae; metum with shallower anterior emargination; tarsal formula 4-4-4......................................................... 8
– Labrum not large and robust; mandible less elongate; labial palpi with 3 indistinct articles; ligula without minute setae; metum with deeper anterior emargination; tarsal formula 3-3-4 or 4-4-5................................................ 9
8. Antennomeres 6–10 subquadrate; anterior margin of labrum truncated; labial palpomere 1 as wide as 2; median lobe smaller; apical process of median lobe broader; apical internal sclerite rounded (fig. 10L in Sawada, 1971); distributed in Japan.................................................................................................. D. uenoi
– Antennomeres 6–10 transverse; anterior margin of labrum rounded (Fig. 3A); labial palpomere 1 wider than 2; median lobe bigger; apical process of median lobe narrower; apical internal sclerite larger and polygonal (Fig. 4D); distributed in Korea........................................................................................... D. submarina
9. Elytron wider than long......................................................................... D. harteri
– Elytron longer than wide.............................................................................. 10
10. Head rounded, as long as wide; antennomeres 8–10 subquadrate; tarsal formula 3-3-4; median lobe (fig. 6 in Yoo and Ahn, 2021)...................................................................................... D. koreana
-– Head oblong, longer than wide; antennomeres 8–10 trransverse; tarsal formula 4-4-5............................... 11
11. Infraorbital carina incomplete, reaching to half of head; median lobe (fig. 42 in Ahn, 1996); distributed in California................................................................................................. D. vandykei
– Infraorbital carina complete, reaching to eye; median lobe (fig. 12 in Song et al., 2018); distributed in Hokkaido.. D. oharai