Hydraena koma, Perkins, 2011

Perkins, Philip D., 2011, New species (130) of the hyperdiverse aquatic beetle genus Hydraena Kugelann from Papua New Guinea, and a preliminary analysis of areas of endemism (Coleoptera: Hydraenidae) 2944, Zootaxa 2944 (1), pp. 1-417 : 58

Hydraena koma , new species

( Figs. 86 , 88 , 469 )

Type Material. Holotype (male): Eastern Highlands Province: Koma River , tributary of Fio River , 100 m downstream of rattan bridge crossing, ca. 3.8 km S by E of Herowana airstrip, washed from margins of small pool of a steep, rocky, forest stream at confluence with river; gravel, cobbles, wet rock microhabitats, 1100 m, 6° 40' S, 145° 12' E, 31 v 2004, N. Porch ( ANIC).

Differential Diagnosis. Somewhat similar in habitus to H. biundulata ( Tetana group), including the shape of the sides of the pronotum, which are nearly equally sinuate in front of and behind the widest part ( Figs. 75 , 86 ); distinguished therefrom by the markedly arcuate anterior margin of the pronotum, the very different metaventral plaques, and the different elytral coloration. Additionally, males have very differently shaped tibiae in the two species. The male genitalia of the two species differ greatly ( Figs. 77 , 88 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.64/0.63; head 0.29/0.36; pronotum 0.38/0.45, PA 0.38, PB 0.36; elytra 0.96/0.63. Dorsum of head with frons and clypeus piceous; labrum dark brown; pronotum light brown to testaceous in front of and behind piceous fascia, ratios of color bands, as measured in midline, ca. 6/15/5; elytra dark brown to piceous in ca. anterior 2/5 and narrowly along explanate margin, otherwise elytra light brown to testaceous; legs light brown; maxillary palpi testaceous, tip not darker. Dorsum moderately strongly shining.

Frons punctures ca. 1xef, only slightly larger near eyes, sparser medially; interstices shining, medially 2–5xpd. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate and shining medially. Mentum and postmentum conjointly weakly concave. Mentum effacedly microreticulate, very sparsely very finely punctulate, weakly shining. Postmentum microreticulate, dull. Genae very slightly raised, weakly shining, with small median impression, without posterior ridge. Pronotum subcordiform, distinctively narrowed both in front of and behind widest area; ca. median 1/2 of anterior margin rather markedly arcuate to posterior; punctures on disc ca. 1xpd largest frons punctures, interstices shining, ca. 2–5xpd, punctures anteriorly and posteriorly ca. 2xpd those on disc, and denser; PF1 and PF4 absent; PF2 very shallow, obsolete; PF3 deep, wide.

Elytra widest at about midlength; summit of posterior declivity at about 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. 1–2xpd, as are interstices between punctures of a row. Apices partly missing in holotype.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/6/5. P1 laminate; median carina sinuate in profile, slightly raised between coxae. P2 length/width ca. 5/3, sides very slightly diverging toward blunt apex. Plaques carinate lines, gradually raising from anterior to posterior, at sides of median depression, anteriorly slightly convergent. Metaventrite flat or slightly concave between mesocoxae. AIS width at straight posterior margin ca. 1.5x P2. All legs of moderate length. Profemur (male) with minute tubercle on ventral margin near trochanter; protibia straight, medial margin widened from about midlength to subapically, then narrowed to apex, greatest width ca. 1.5x width at midlength. Mesotibia straight, slender, with many short spine-like setae. Metatibia with medial margin distinctly widened at about midlength, greatest width ca. 1.5x width at apex; lateral margin emarginate. Abdominal apex symmetrical; last tergite (male) with large, deep apicomedian notch. Aedeagus as illustrated ( Fig. 88 ).

Etymology. Named in reference to the Koma River.

Distribution. Currently known only from the type locality, the Koma River in southeastern Area 1, near where Area 1 borders Area 13; elevation 1100 m ( Fig. 469 ).

Figures

FIGURE 75. Hydraena biundulata, holotype, dorsal and lateral habitus, and venter.

FIGURE 86. Hydraena koma, holotype, dorsal and lateral habitus, and venter.

FIGURES 88–89. Aedeagi of holotypes. 88. H. koma. 89. H. colorata.

FIGURES 467–470. Geographical distributions of Hydraena species.

FIGURES 76–77. Aedeagi of holotypes. 76. H. insandalia. 77. H. biundulata.