Hydraena impercepta Zwick, 1977

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 : 62-63

Hydraena impercepta Zwick, 1977

(Figs. 88, 93, 241)

Hydraena impercepta Zwick, 1977: 153 .

Type Material. Holotype (male): Queensland [labels: Queensland Blackb's Coll // luridipennis, Macl. // I 8298 Hydraena luridipennis Macl Queensland // Hydraena impercepta Zwick spec. nov. Holotypus male design. P. Zwick 1975 // DIGITAL IMAGE captured 2004 P. D. Perkins]. Deposited in the SAMA.

Differential Diagnosis. Recognized by the combination of the large body size (ca. 2.00 mm), the absent, or nearly absent, plaques, and the unique shape of the male metatibiae (Fig. 88), which are widened on the inner surface near midlength. This species is similar in size and dorsal sculpture to H. simplipes and H. luridipennis , but differing therefrom in the shape of the male metatibiae; also differing from H. luridipennis in shape of the pronotum (Fig. 86). The aedeagi of the three species are quite distinct (Figs. 91, 93, 94).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.00/0.88; head 0.25/ 0.45; pronotum 0.49/0.64, PA 0.49, PB 0.59; elytra 1.29/0.88. Head and large pronotal macula dark brown, remainder of dorsum, legs and maxillary palpi brown.

Frons punctures ca. 1xef; interstices narrow walls near eyes, 1–3xpd medially. Clypeus microreticulate laterally, finely punctate medially. Mentum shining, very finely sparsely punctate; postmentum microreticulate. Genae raised, lacking posterior ridge. Pronotum densely coarsely punctate, punctures on disc deep, ca. 3xpd those of frons, interstices narrow walls to 1xpd, some interstices uniting to form short longitudinal lines; PF1 absent; PF2 shallow; PF3 and PF4 moderately deep, shallowly joined.

Elytral punctures about 0.5xpd of largest pronotal punctures. Intervals not raised, width ca. 1xpd, interstices between punctures of a row slightly less. Apices in dorsal aspect separately rounded, in posterior aspect margins forming angle with one another.

Metaventral disc densely punctate beneath hydrofuge pubescence, without plaques, median impression deep, longitudinal, subtriangular, basally ca. 2x P2. P1 laminate; median carina angulate in profile. P2 moderately narrow, l/w ca. 5/3, sides parallel, apex rounded. Very low midlongitudinal carina between mesoventral intercoxal process and median depression. AIS flat, width at arcuate posterior margin 2x P2. Abdominal apex with short setae; last tergite with depression on ventral face. Protibia with subapical angulation on inner surface. Mesotibia slender. Metatibia with rounded enlargement on inner surface near midlength, then tapering to apex; outer surface arcuate at base, then straight to apex.

Aedeagus (Fig. 93) main-piece slightly wider in lateral than ventral view, with large, strong process on right side of apical part, medial margin with two points; left paramere large, with four groups of setae; right paramere narrow, with three groups of setae. Female last tergite with minute apicomedian incision, or no incision; setae stout, forming a row, tips blunt and angled ventrad.

Distribution. Currently known from Queensland and northern Northern Territory (Fig. 241). Also present in Papua New Guinea (Perkins, unpublished).

Remarks. In females the elytral apices are slightly more sharply rounded, the posterior declivity is not as abrupt, and the metaventral depression is not as deep as in males. Some specimens have the metaventral plaques apparent as very small, non-punctate ovals at the base of the median depression.

Material Examined (110): Northern Territory, 1 km N of Cahills Crossing, East Alligator River , 12° 25' S, 132° 58' E, 7 June 1973, Upton & Feehan (2 ANIC) ; 10 mi E of Daly River , at light, 13° 45' S, 130° 51' E, 28 June 1972, B. K. Head (15 SAMA) ; 16 km E by N of Mt. Cahill , 12° 51' S, 132° 42' E, 13 June 1973, Upton & Feehan (1 ANIC) ; 5 km NNW Cahills Crossing, East Alligator River , 12° 23' S, 132° 57' E, 28 May 1973, E. G. Matthews (1 ANIC) ; 5 km NW by N of Cahills Crossing, East Alligator River , 12° 35' S, 132° 56' E, 27 May 1973, E. G. Matthews (1 ANIC, 1 NMW); 7 km NW by N of Cahills Crossing, East Alligator River , 12° 23' S, 132° 56' E, 27 May 1973, E. G. Matthews (2 ANIC) ; Darwin , 12° 27' S, 130° 50' E, 13 May 1963, C. Watts (4 SAMA) ; Koongarra , 15 km E of Mt. Cahill , 12° 52' S, 132° 50' E, 12 June 1973, Upton & Feehan (1 ANIC) ; Queensland, 10 km S Tully, S Innisfail , elev. 30 m, 17° 32' S, 146° 2' E, 25 January 1993, Wewalka (26) (5 NMW) ; 15 km WNW Johnstone , light trap, 17° 36' S, 145° 55' E, 1–30 May 1987, Fay & Halfpapp (1 QPIM) ; 15 to 20 km S Innisfail , elev. 20 m, 17° 32' S, 146° 2' E, 24 January 1993, Wewalka (1 NMW) ; 18 km N Mareeba , intermittent stream, 16° 58' S, 145° 25' E, 20 September 1990, D. Larson (1 MCZ) ; 20 km N Mareeba , 16° 58' S, 145° 25' E, 20 September 1990, D. & M. Larson (8 MCZ) ; 30 km NW Brisbane, South Pine River , elev. 120 m, 27° 21' S, 152° 47' E, 21 August 2004, M. A. Jäch (AU 2) (3 NMW) ; 4 km S Yungaburra , 17° 17' S, 145° 34' E, 6 November 1990, D. Larson (2 MCZ) ; 5 km NW Mt. Molloy , 16° 36' S, 145° 16' E, 5 February 1997, C. Watts (1 SAMA) ; Barron River, Mareeba , 16° 58' S, 145° 25' E, 15 September 1990, D. Larson (1 MCZ) ; Brisbane , 27° 22' S, 152° 46' E, 1–30 January 1961, C. Watts (1 SAMA) ; Bushland Beach, 12 km N Townsville , 19° 12' S, 146° 41' E, 6–11 February 1998, A. J. Watts (8 SAMA) ; Caloundra , 26° 48' S, 153° 8' E, 26 March 1963, C. Watts (1 SAMA) ; Greenvale , 150 km NW Charters Towers , elev. 500 m, 19° 0' S, 144° 58' E, 19 January 1993, Wewalka (1 NMW) ; L. Mitchell R ., 40 km N Mareeba , 16° 58' S, 145° 25' E, 21 September 1990, D. Larson (1 MCZ) ; Mia Mia State Forest, between Finch Hatton & Pinnacle, Cattle Creek , 21° 14' S, 148° 47' E, 16 March 1997, P. Zwick (1 PZC) ; Moggill , 27° 32' S, 152° 56' E, 4 March 1933, H. Hacker (2 QMBA) ; Nardello's Lagoon, 15 km S Mareeba , 16° 58' S, 145° 25' E, 20 December 1990, D. Larson (1 MCZ) ; SE Atherton, Swamp , 17° 16' S, 145° 28' E, 6 November 1990, D. Larson (5 MCZ) ; Townsville , elev. 10 m, 19° 15' S, 146° 48' E, 17 January 1993, Wewalka (2 NMW) ; West Barron Balancing Reservoir , ca . 15 km W Mareeba , 16° 58' S, 145° 25' E, 30 June 1991, D. Larson (28 MCZ) ; Windsor Tableland , 38 km from main road, 16° 13' S, 145° 2' E, 28 November 1985, Storey & Brown (1 QPIM) ; Yungaburra, Atherton Tableland , 17° 16' S, 145° 36' E, 30 March 1932, P. J . Darlington (6 MCZ) .