Hydraena mitchellensis, Published, 2007

PERKINS, PHILIP D., 2007, A revision of the Australian species of the water beetle genus Hydraena Kugelann (Coleoptera: Hydraenidae), Zootaxa 1489 (1), pp. 1-207 : 13-14

Hydraena mitchellensis new species

( Figs. 2 , 7 , 250)

Type Material. Holotype (male): Western Australia, 4 km S by W Mining Camp, Mitchell Plateau , 14° 52' S, 125° 50' E, 13 May 1983, D. C. F Rentz, J. Balderson (17). Deposited in the ANIC . Paratypes: Same data as holotype (7 ANIC) .

Differential Diagnosis. Externally very similar to other members of the reticulata Group ( Figs. 1–4 ); reliable determinations will be based on study of the aedeagus. Similar to H. reticulata in the absence of plaques; differing therefrom in the smaller size (ca. 1.38 vs. 1.21 mm), and details of the aedeagus ( Figs. 5–7 ).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.38/0.58; head 0.23/ 0.37; pronotum 0.35/0.49, PA 0.39, PB 0.43; elytra 0.82/0.58. Dorsum dark brown, dull; legs brown; palpi light brown except distal 2/3 of last palpomere darker. Head and pronotum markedly microreticulate, setae short but distinctive.

Frons punctures ca. 1xef; interstices ca. 1xpd. Mentum finely sparsely punctate. Postmentum microreticulate. Genae weakly raised, lacking posterior ridge. Pronotal punctures on disc slightly larger than those of frons, interstices ca. 1xpd; PF1 absent; PF2 deep, oblique, separated by about width of a fovea; PF3 moderately deep, broad; PF4 moderately deep, broad.

Elytral punctures slightly larger than largest pronotal punctures. Intervals not raised, very effacedly microreticulate, width about 1xpd, interstices between punctures of a row narrower, each puncture with distinctive short seta. Apices in dorsal aspect conjointly rounded, in posterior aspect margins form moderately strong angle with one another.

Plaques absent, median depression wide, moderately deep. P1 laminate; median carina angulate in profile. P2 narrow, l/w ca. 2/1, sides weakly converging, apex blunt. AIS flat, width at arcuate posterior margin 2–3x P2. Protibia (male) near distal 2/3 slightly widened and medial surface with small, sharp tubercle, row of short setae between tubercle and apex of tibia; mesotibia simple; metatibia straight on medial margin, lateral margin extremely weakly arcuate, without setal brush. Abdominal apex symmetrical.

Aedeagus ( Fig. 7 ) main-piece with moderately large pointed process on right side; left paramere widest subbasally, then tapering to narrow tip which ends at level of midlength of flagellum, setae sparse, in a row on ventral margin; right paramere widened in distal 1/2, setae in row along ventral margin and tip. Female last tergite without incisions, with two transverse ridges, setae slender, tapering.

Etymology. Named in reference to the geographical distribution.

Distribution. Currently known only from the type locality in the Mitchell Plateau, northeastern Western Australia (Fig. 250).

Figures

FIGURES 1–4. Hydraena, dorsal and lateral habitus of holotypes. —1. H. reticulata. —2. H. mitchellensis. —3. H. reticuloides. —4. H. reticulositis.

FIGURES 5–8. Aedeagi of holotypes. —5. H. reticulata. —6. H. reticulata (after Zwick 1977). —7. H. mitchellensis. —8. H. reticuloides.