Carabhydrus andreas Zwick, 1981

Hendrich, Lars & Watts, Chris H. S., 2009, Taxonomic revision of the Australian predaceous water beetle genus Carabhydrus Watts, 1978 (Col. Dytiscidae, Hydroporinae, Hydroporini), Zootaxa 2048 (1), pp. 1-30 : 5-10

Carabhydrus andreas Zwick, 1981

( Figs 1 , 10, 11 , 29 , 30, 31 )

Carabhydrus andreas Zwick, 1981: 167 ; Watts (1985: 23); Larson & Storey (1994: 895, 900); Nilsson (2001: 144); Watts (2002: 32, 44).

Type locality: East Tanjil River , at foot of Mt. Baw Baw, Victoria, Australia .

Type material: Holotype: 1 male: “ Australia, Victoria, E Tanjil R. [River] at foot of Mt. Baw Baw [ Baw Baw National Park ] 27.IV.1972 P. Zwick ” [hw white label], “ Carabhydrus andreas Zwick ♂ holotype [hw white label]”, “ Holotype ♂ T-16705 Carabhydrus andreas Zwick ” [red printed label] ( NMV).

Additional material studied (14 specimens): Victoria: 1 ex., Acheron River, Narbethong , 9.IV.1996, P.S. Lake leg., SAMA Database No 25-003757 ( SAMA) ; 3 exs., Sardine Creek , 30 km N Orbost, 16.I.1997, C. Watts leg., SAMA Database No 25-003758 ( SAMA) ; 1 ex., Errinundra River 14.IX.2003, 37.24S 148.53E, A. Glaister leg., SAMA Database 25-012890 ( SAMA) ; 1 ex., Little R [River], Taggerty , 12.III.1996, 37.20S 145.43E, P.S. Lake & B.J. Downs et al. leg., SAMA Database 25-009299 ( SAMA) ; 1 ex., Little R Taggerty , 9.IV.1996, 37.20S 145.43E, P.S. Lake & B. J. Downs et al. leg., SAMA Database 25- 003756 ( SAMA) ; 1 ex., Roadnight Creek / Tambo R [River] branch W of Forrest, 1.II.2004, 38.30.94S 143.41.42 E, A. Glaister leg., SAMA Database 25-012889 ( SAMA) . New South Wales: 1 ex., NSW EPA Survey MRHI Murchison River (m1), Bago Creek , 35.33.57S 148.01.58E, 20.III.1996, Natacha Waddell leg. ( AM) . Australian Capital Territory: 1 ex., Gibraltar Falls near Tharwa , 23.XII.1973, S. Britton leg. ( ANIC) ; 3 exs., Corin Road, Gibraltar Falls, Gibraltar Creek , 987 m, 10.II.1998, 35.29.137S 148.56.150 E, L. Hendrich leg. (35/76) ( CLH) ; 1 ex., Gibraltar Falls Picnic Area , 987 m, 11.XI.2006, 35.29.137S 148.56.150 E, L. & E. Hendrich leg. (ACT 98) ( ZSM) .

Re-description: Measurements: TL = 2.4–2.6 mm, TL-H = 2.15–2.3 mm, MW = 0.9–1.1 mm.

Color ( Fig. 1 ): Almost black, anterior margin of clypeus, antennae, palpi and legs pale yellowish. Two large basal elytral marks extending to sides but not to suture, and two apical spots of elytra pale reddish brown. Ventral surface black except reddish brown epipleura and last two abdominal segments.

Sculpture: Head anterior to dorsal impression with deep punctures separated by a distance about 1 ½ equal to their own diameters, and a few sparse, minute punctures; interspaces smooth and shiny, microreticulate along hind edge on a strip along small eyes, and in two shallow depressions medially from indistinct swellings above insertion of antennae.

Pronotum shining sparsely punctuate medially in front, denser on rest of surface but difficult to see because of many small wrinkles connecting punctures, microreticulation absent. Wrinkles transverse in basal half. Strongest between striae, fine and directed anteriorly or obliquely to outside near front ends of striae.

Elytron with dual irregular punctation similar to that of pronotum but more dense, surface somewhat uneven especially near middle, here punctures larger, near tip fine. Only apex of female with evident microreticulation; epipleura simple, distally narrowed, disappears in distal fifth with dense, more or less contiguous punctures.

Ventral surface with punctures similar in size or slightly smaller than those of dorsal surface, denser and more irregular with surfaces of sclerites irregularly rugose; punctures of metacoxal plate and sterna 1 and 2 not evidently larger than those elsewhere on ventral surface; metasternum medially and metacoxa between metacoxal lines sparsely and finely punctate. Legs with femora, tibiae, and dorsal surface of metatarsomeres 1–3 strongly punctate.

Structure: Head very broad, with deep cervical stria between posterior edge of eyes. Lateral margins of clypeus somewhat produced laterally above insertion of antenna; frontal fovea distinct, ovate; dorsal surface with a strong transverse impression between posterior margins of eyes; maxillary and labial palpi each with apical palpomere fusiform.

Pronotum slightly transverse, strongly cordiform, base distinctly narrower than head. Basal half flat, anterior part curved down, especially near projecting anterior angles, here with a slight depression, parallel to rear margin of head. Lateral margin in dorsal aspect more or less evenly rounded except shortly sinuate before obtuse posterolateral angle; lateral bead sharply defined, narrow; basal margin slightly lobed medially; disc broadly convex in apical half, flattened basally and narrowly flattened adjacent to lateral margin; disc with a pair of longitudinal impressions, each extending from convex mediolateral portion of disc almost to hind margin and strongly limited on outer side by a more or less carinate ridge, mesal margin less distinct; most specimens with one to several additional shorter and more irregular rugae or impressions as well as elongate punctures along basal margin adjacent to major impressions. Scutellum visible, short and broad.

Elytra together elongate-oval with point of maximum width near middle, sides converging basally; disc of each elytron with a medial and a sublateral, broad, longitudinal groove each bearing a row of serial punctures, and a less evidently defined lateral groove adjacent to lateral margin; medial and sublateral groove beginning approximately opposite basolateral impression of pronotum, sharply defined on basal three-fourths, becoming shallower apically.

Ventral surface, lateral portions of thorax and abdomen narrowed ventrally, medially forming a more or less flattened area comprising prosternal process, medial area of metasternum, intralinear space of metacoxae, and abdominal sterna medially. Prosternum with anterolateral pore well removed from anterior margin. Prosternum and its process in lateral aspect in almost the same plane; process hardly deflexed, grooved in middle, sides raised, oval. Metasternum largely in a vertical plane, prosternal process touching metasternum between mesocoxae. Metasternum medially flat, faintly raised anteriorly joined lines extend from between mesocoxal plates posteriorly, here becoming indistinct. Metacoxal lines strongly raised, first directed a little outward as usual but their front ending curved medially. Metacoxal process flat, distally hardly sinuous, indistinctly notched in middle.

Legs long. Coxae and trochanters normal. Femora simple, metafemur shorter than others and much shorter than tibia. All femora largely visible from above. Profemur with anteroventral margin slightly emarginate sub-apically and fringed with a row of short, stout setae. Protibia with medially enlarged apical half, a regular row of very fine and short setae on inside below. Apex oblique on outside, with several spines. Three basal tarsal segments much enlarged, symmetrical, with adhesive hairs below and long fine hairs above. Protibia with medially enlarged apical half, a regular row of very fine short setae on inside below. Apex oblique on outside, with several spines. Normal spurs present. Three basal tarsal segments much enlarged, symmetrical, with adhesive hairs below and long fine hairs above. Segment 4 minute, fifth slender, long, with equal slender claws. Mesotibia straight, inner face with long hairs. Pro- and mesotarsomeres 1–3 ovate; protarsomere 4 small, situated within emargination of tarsomere 3 but visible in dorsal aspect. Hind legs slender; metatibia straight, evenly broadened from base to apex, natatorial setae absent from ventral face in both sexes, longer metatibial spur about two-thirds length metatarsomere 1; metatarsomeres elongate; metatarsal claws equal.

Male: Antenna only slightly broadened, antennomeres 5–7 very slightly and progressively widened, antennomeres 8–10 1.5 time a long as wide, 11 fusiform. Profemur with anteroventral margin bearing four basal and a medial, short, stout spines. Protibia enlarged anteriorly with mesal margin bearing a low, obtuse, subapical tooth and a basal row of short, pale setae. Protarsomeres 1–3 slightly dilated. Mesofemur clavate, ventral margin flattened and bearing a brush of elongate golden setae; mesotibia without subapical tooth. Metatibia with basal natatorial setae of mesal face elaborated into a brush of long, yellow setae. Paramere sclerotized, broad, symmetrical, almost square, much shorter than aedeagus, glabrous except for a few long setae along distal margin; median lobe of aedeagus ( Figs 10, 11 ) slender strongly bent, apex with upper and lower flanges separated by steep lateral sulci. Apex in ventral view lanceolate, widest at origin of sulcus, seemingly ending in a sharp point. Lower flanges narrower than upper, strongly constricted basally, much longer than upper flanges and extending far beyond apparent dorsal tip, forming a bifid anterior process. Both portions of anterior process long, flat, blade-like, obliquely positioned with straight inner edge up and curved outer edge down, tip narrow.

Female: Metatibia with a small group of natatorial setae arising in basal half of mesal face. Females a bit larger than males. Measurements: TL = 2.5–2.6 mm, TL-H = 2.25–2.3 mm, MW = 1.0– 1.1 mm.

Differential diagnosis: A distinct species which can be easily separated from all other species of the genus by its body shape ( Fig. 1 ), characteristic maculate elytra, the sharp cervical and elytral striae and by the shape of the median lobe ( Figs 10, 11 ). Carabhydrus niger ( Fig. 9 ) and C. mubboonus ( Fig. 7 ) have similarly long elytral striae but are almost completely black and have a different shaped median lobe. The only species which superficially looks like C. andreas is C. turaki sp.n. ( Fig. 5 ) but the latter is more flattened, its pronotum is less cordiform and it has deeper and more strongly grooved elytral and pronotal striae.

Distribution: Mountain regions of SE Australia. From southern New South Wales along the Great Dividing Range to eastern Victoria ( Fig. 29 ). Not on Tasmania. After C. niger the most widespread species of the genus.

Habitat: Collected from nutrient poor, oxygen rich permanent streams, smaller rivers and slow flowing creeks up to an altitude of 987 m, from more or less open country to closed-canopy forest sites ( Figs 30, 31 ). Most specimens were found in low-gradient stream or river sections where the substrate was entirely coarse sand, rocks, and smaller logs or rotten twigs yet the current was strong enough to clean the bottom of silt and leaves. In this habitat the beetles were found in areas of slow, laminar flow, generally under larger stones and logs. All specimens were captured by disturbing the bottom and moving the larger rocks and stones then vigorously sweeping the area with a stout aquatic net. The population density of C. andreas seems to be quite low as it was not possible to collect more than two or three specimens on one spot per visit on different times.

Figures

FIGURES 1–4. Habitus of Carabhydrus. 1—Carabhydrus andreas (male); 2—C. innae sp.n. (holotype, male); 3—C. plicatus; 4—C. storeyi sp.n. (paratype, male) (scale bar 1 mm) (Photos: L. Hendrich).

FIGURES 10–19. Median lobe of aedeagus in ventral and lateral view (scale bar 0.2 mm): 10, 11—Carabhydrus andreas and 12, 13—C. innae sp.n.; 14, 15—C. innae sp.n. right paramere (14) and first two mesotarsal segments (15) in dorsal view (scale bar 0.2 mm). Median lobe of aedeagus in ventral and lateral view: 16, 17—C. janmillerae sp.n. and 18,19—C. monteithi.

FIGURES 28–29. Distribution of the genus Carabhydrus in Australia.

FIGURES 30–35. Habitats of 30,31—C. andreas, Gibraltar Falls, downstream and upstream (ACT), November 2006; 32—C. niger, NW Tasmania, Detention River, 2.5 km SW Mawbanna, December 2006; 33—C. niger, 13 km NNW Dungog, Williams River, Tillegra Bridge, October 2006; 34, 35—C. innae sp.n., Thomson River in Baw Baw National Park (Victoria) (Photos L. Hendrich).

FIGURES 5–9. Habitus of Carabhydrus. 5—Carabhydrus turaki sp.n. (holotype, female); 6—C. stephanieae (paratype); 7—C. mubboonus (female); 8—C. janmillerae sp.n. (paratype, female); 9—C. niger (female) (scale bar 1 mm) (Photos: L. Hendrich).