Hydraena divisa, Perkins, 2017

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 120-121

Hydraena divisa , new species

Figs. 107 (habitus), 109 (aedeagus), 279 (map) Type Material. Holotype (male): Antsiranana, Antsaba,Galoko Mountains, hygropetric cascade, elev. 303 m, 13° 39' S, 48° 45' E, 1 xi–29 xii 2004, M. Balke (MD 016) (ZSMC). Paratypes: Same data as holotype (4 ZSMC).

Differential Diagnosis. The smallest member of the species group (ca. 1.53 mm). Differentiated from other members by the short, narrow, widely separated metaventral plaques; the plaques are separated by slightly more than the length of the plaques. The aedeagus is also readily distinguished from that of other members of the group

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.53/0.61; head width 0.36; pronotum 0.36/0.48, PA 0.40, PB 0.41; elytra 0.89/0.61.

Dorsum dark brown to piceous, head darkest; legs brown; maxillary palpi light brown, distal 0.5 of last palpomere (except tip) slightly darker.

Head with dorsal punctation very uniform, moderately coarse and rather dense; interstices ca. 0.5xpd, weakly shining. Mentum finely sparsely punctulate, interstices strongly shining; postmentum densely, more coarsely punctate, interstices shining. Genae roundly raised, medially smooth and shining, without posterior ridge.

Pronotum arcuate laterally; anterior margin straight behind eyes, very slightly emarginate behind frons. Pronotal punctures larger than those of head, dense and quite uniform in size, interstices narrow walls to ca. 0.5xpd, weakly shining. PF1 shallow; PF2 shallow, very shallowly confluent medially; PF3 deep; PF4 shallow.

Elytra weakly arcuate laterally; summit of posterior declivity near midlength; lateral explanate margins moderately wide; serial punctures round, very closely spaced, separated by ca. 0.5xpd or less, slightly large than pronotal punctures. Intervals not raised, ca. 0.5xpd,very weakly shining. Apices in dorsal aspect conjointly rather sharply rounded, in posterior aspect margins do not form shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/2 /2. P1 laminate; median carina sinuate in profile. P2 l/ w (w at apex) ca. 2/1, sides parallel, apex blunt and raised slightly above metaventral intercoxal process. Plaques small, oval, parallel, not raised, located at sides of shallow median depression. Metaventrite with very short process on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at arcuate posterior margin ca. 2x P2. Protibia very slightly arcuate, almost straight, slightly widened at ca. distal ¼. Mesotibia straight, widest at ca. midlength. Metatibia very weakly arcuate, medial margin with small brush of setae in distal 0.5. Metafemur not markedly arcuate on lateral and medial margins. Abdominal apex with moderately deep asymmetrical notch.

Etymology. Named in reference to the widely separated metaventral plaques.