Hydraena cheesmanae, 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 : 46

Hydraena cheesmanae , new species

( Figs. 59 , 61 , 458 )

Type Material. Holotype (male): Central Province: Kokoda , under stones, river side, 365 m, 8° 39' S, 147° 15' E, 1–30 viii 1933, L. E. Cheesman (577) ( NHM) . Paratypes: Same data as holotype (21 NHM) .

Differential Diagnosis. Similar in dorsal habitus to H. otiarca ( Figs. 55 , 59 ); differing therefrom in slightly smaller size (ca. 1.37 vs. 1. 46), less coarsely punctate pronotum, with PA and PB equal (PA slightly wider than PB in H. otiarca ), a slightly larger pronotal fascia, and having the metaventral plaques slightly shorter and more widely separated (ratios ca. 3/3/8/3 vs. 3/2/9/2). The male metatibiae differ very slightly in the two species, whereas the male genitalia differ distinctively in many details ( Figs. 57 , 61 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.37/0.59; head 0.19/0.34; pronotum 0.34/0.41, PA 0.35, PB 0.35; elytra 0.83/0.59. Dorsum of head piceous; pronotum light brown to testaceous in front of and behind piceous fascia, ratios of color bands, as measured in midline, ca. 6/12/5; elytra dark brown; legs brown; maxillary palpi light brown to 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 anterior 1/2 of postmentum very sparsely very finely punctulate, shining; distal 1/2 of postmentum micropunctulate. Genae raised, shining, without posterior ridge. Pronotum cordiform, median 1/2 of anterior margin emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 2–3xpd, punctures larger and denser at anterior and posterior; PF1 absent; PF2 very shallow, obsolete; PF3 deep; PF4 absent.

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

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/3/8/3. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward blunt apex. Plaques large, converging slightly anteriorly, weakly transversely raised, at sides of deep median depression, each plaque tapering slightly from posterior to anterior. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin slightly greater than P2. All legs long and slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia very slightly arcuate, widest subapically, cluster of small spines on medial margin at apex, moderately long spine on medial surface at ca. distal 1/3. Mesotibia straight. Metatibia weakly bent at midlength, distal 1/2 slightly widened. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 61 ).

Etymology. Named in honor of the intrepid Englishwoman entomologist and naturalist Lucy Evelyn Cheesman, who collected the only known specimens of this species — in 1933! During August of that year she collected a total of five species of Hydraena at Kokoda.

Distribution. Currently known only from the type locality, Kokoda, in Area 7; elevation 365 m ( Fig. 458 ).

Figures

FIGURE 55. Hydraena otiarca, holotype, dorsal and lateral habitus, and venter.

FIGURE 59. Hydraena cheesmanae, holotype, dorsal and lateral habitus, and venter.

FIGURES 60–61. Aedeagi of holotypes. 60. H. remulipes. 61. H. cheesmanae.

FIGURES 455–458. Geographical distributions of Hydraena species.

FIGURES 56–57. Aedeagi of holotypes. 56. H. infoveola. 57. H. otiarca.