Hydraena koje Perkins 2011, new species

Hydraena koje, new species

(Figs. 215, 217, 528)

Type Material. Holotype (male): Madang Province: Sepik Ramu Basin, Kojé Creek, unshaded creek, small to medium cobbles, gravel and fine sand (the latter in areas of slack water), filamentous algae on stony substrates, small accumulations of leaf litter, 160 m, 5° 33' S, 145° 23' E, 1 vii–30 viii 1988, D. Dudgeon (NMW). Paratypes: Same data as holotype (98 NMW).

Differential Diagnosis. Similar in small size (ca. 1.29 mm) and color to H. tritropis (Figs. 211, 215); differing therefrom by the narrower body, the proportionally smaller pronotum (PW/EL ca. 0.59 vs. 0.66), the concave prosternal intercoxal process, and the narrower mesoventral intercoxal process (plaque ratios ca. 6/1/5/5 vs. 7/1/5/5). The male genitalia of the two species show some similarity in basic plan, but distinctively differ in many details (Figs. 213, 217).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.29/0.57; head 0.21/0.32; pronotum 0.30/0.46, PA 0.35, PB 0.37; elytra 0.78/0.57. Dorsum generally reddish brown, frons and elytra distinctly more darkly colored than pronotum and clypeus; legs light brown to light reddish brown; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–2xef, larger near eyes than medially; interstices shining, 1–4xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, without posterior ridge. Pronotum subcordiform, ca. median 3/4 of anterior margin arcuate to posterior; punctures on disc ca. 1xpd frons punctures, interstices shining, 1–3xpd, punctures slightly larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 very shallow; PF3 moderately deep; PF4 very shallow.

Elytra with summit of posterior declivity slightly anterior to midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1–3xpd, as are interstices between punctures of a row. Apices in dorsal aspect slightly separately rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 6/1/5/5. P1 ca. 2/3 P2; median carina straight in profile; postcoxal process medially concave. P2 transversely concave, l/w ca. 5/6, sides slightly diverging toward blunt apex. Plaques very narrow, carinate, converging slightly anteriorly, at sides of deep median depression. Metaventrite concave between P2 and plaques. AIS width at straight posterior margin ca. equal P2. All legs moderately long and slender. Profemur (male) without tubercle next to trochanter; protibia slightly arcuate. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated (Fig. 217).

Etymology. Named in reference to the type locality.

Distribution. Currently known only from the type locality, Kojé Creek, in the eastern arm of Area 3; elevation 160 m (Fig. 528).