Hydraena pilobova, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 117-120

Hydraena pilobova , new species

Figs. 104 (habitus), 106 (aedeagus), 278 (map)

Type Material. Holotype (male): Antsiranana, Sava , Marojejy NP, 800m N from Camp I, Humbert waterfall ; 14.4333S 49.773E, ex. bedrock pools at side of waterfall, elev. 550 m, 8 xi 2014, P. D. Perkins (MAD14-48) (NHRS). Paratypes (86): Same data as holotype (48 NHRS). Antsiranana, 14.4329S 49.7592E Sava Marojejy NP 500m W from Camp II, big rocky forest stream, elev. 640 m, 14° 25' S, 49° 45' E, 10 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-57 ) (6 NHRS) ; 14.4354S 49.768E Sava Marojejy NP 1km along main path from Camp I to Camp : forest stream with some pools, stones and dead leaves, elev. 590 m, 14° 26' S, 49° 46' E, 9 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-53 ) (1 NHRS) ; 14.4369S 49.7749E Sava Marojejy NP 300m N from Camp I, upstream, waterhole with dead leaves next to the stream, elev. 490 m, 14° 26' S, 49° 46' E, 8 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren ( MAD14-50 ) (27 NHRS); Marojejy NP , 800m N from Camp I, Humbert waterfall; 14.4333S 49.773E, waterfall, elev. 550 m, 14° 26' S, 49° 46' E, 8–12 xi 2014, J. Bergsten, R. Bukontaite, J.H. Randriamihaja, T. Ranarilalatiana & S. Holmgren (MAD14- 48) (4 NHRS).

Differential Diagnosis. The largest member of the group (ca. 2.09 mm). Males differentiated from others by the form of the metatibiae: very slightly arcuate, medial margin distinctly widened from ca. midlength to apical ¼, and bearing at widened area large brush of arcuate setae, setal bases in line at ca. middle of enlarged area of tibia, not on margin. The habitus is similar to that of H. pilotumida , but the male metatibiae and the sixth ventrite differ in the two species. The aedeagi also show a relationship, but differ in shapes of several parts ( Figs. 105, 106).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.09/0.86; head width 0.45; pronotum 0.48/0.64, PA 0.50, PB 0.55; elytra 1.33/0.86.

Dorsum dark brown, head darkest; legs brown to dark brown; maxillary palpi light brown to testaceous, distal ½ of last palpomere darker.

Head and pronotum densely moderately coarsely punctate. Pronotal punctures larger than those of head; interstices varying from narrow ridges to ca. 1xpd, shining. Mentum finely sparsely punctulate, shining; postmentum sparsely, more coarsely punctate, interstices shining. Genae roundly raised, smooth and shining, without posterior ridge.

Pronotum bisinuate laterally, very weakly emarginate between anterior angle and widest part of pronotum; anterior margin straight behind eyes, emarginate behind frons; PF1 very shallow; PF2 shallow, very shallowly, if at all, confluent medially forming very weak U-shaped impression; PF3 deep; PF4 very shallow.

Elytra weakly arcuate laterally; summit of posterior declivity near distal 2/3; lateral explanate margins moderately narrow; serial punctures round, separated by ca. 1xpd, slightly larger than pronotal punctures, some punctures random near scutellum. Intervals very weakly raised, not forming distinct unbroken straight lines, shining, ca. 1xpd. Apices in dorsal aspect broadly conjointly rounded, in posterior aspect margins forming moderately deep angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1.5/2.2/1. P1 laminate; median carina sinuate in profile. P2 l/w ca. 2/1, sides parallel, apex blunt and raised slightly above metaventral intercoxal process. Plaques large, narrowly separated, widest near midlength, anteriorly and posteriorly rounded, converging very slightly anteriorly, slightly raised, located at sides of median depression. Metaventrite with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at arcuate posterior margin ca. 2x P2. Protibia very weakly arcuate, almost straight, slightly widened at ca. distal ¼ and here bearing on medial surface row of short spines, one larger than the others. Mesotibia straight. Metatibia very slightly arcuate, medial margin distinctly widened from ca. midlength to apical ¼, and bearing at widened area large brush of arcuate setae, setal bases in line at ca. middle of tibia, not on margin of enlarged area. Metafemur lateral margin strongly arcuate, medial margin strongly sinuate.

Abdominal apex with deep apicomedian concavity, upper margin bearing short setae and lower margin asymmetrical, with small produced point off center. Ventrite 5 very finely strigose in median area, patch of short setae on each side of area. Ventrite 6 median area slightly concave, bordered posteriorly by short setae.

Etymology. Named in reference to the brush of setae that is located on the widened portion of the male metatibia.