Carabhydrus plicatus Watts, 1978

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 : 20-21

Carabhydrus plicatus Watts, 1978

( Figs 3 , 24, 25 , 28 )

Carabhydrus plicatus Watts, 1978: 28 ; Zwick (1981: 170); Watts (1985: 23); Lawrence et al. (1987: 334); Larson & Storey (1994: 895, 900); Nilsson (2001: 144); Watts (2002: 32, 44).

Type locality: Pine River , Petrie district, Brisbane, SE Queensland, Australia .

Type material: Holotype: 1 male: “ Petrie Dist. Pine River Wassell”, “ Holotype ” [red label printed], “ Holotype Carabhydrus plicatus Det. C. Watts 1976 ”, “ANIC Database No. 25 013194” ( ANIC) . Paratypes: 3 males: “ Petrie Dist. Pine River 20-12-31 Wassell”, “ Paratype ” [red label], “ Paratype Carabhydrus plicatus Det. C. Watts 1976 ”, “ANIC Database No. 25 013196” ( ANIC, SAMA) ; 2 exs.: “N. of Pine River, Brisbane , Queensland, 5-III-1932, Darlington ”, “ Paratype Carabhydrus plicatus Det. C. Watts 1976 ” ( MCZ) .

Additional material studied (5 specimens): Queensland: 1 female, “ Australia N[orth] Pine R[iver], 25.I.[19]32, M. Hacker ” ( QM) ; 1 female, “ Australia Queensland, N[orth] Pine R[iver], 23.I.[19]32, M. Hacker ” ( QM) ; 1 male, 1 female, “ Amamoor Ck 8 km SW of Amamoor Qld 20.22.12S 152 35 59E A Glaister 17/8/04 SAMA Database 25-012868” ( SAMA) . New South Wales: 1 male, “Wollomombi R. [River] 25 m [25 miles on Grafton road east of] Armidale [30.51S 152.04E] 19.IX.1972 Hinton”, “alcohol coll. tube 194”, “ HE Hinton coll. BM 1977-566” “ Carabhydrus plicatus Watts Ribera & Hernando det.” ( BMNH) .

Re-description: Measurements: TL = 2.25–2.45 mm, TL-H = 2.00– 2.15 mm, MW = 0.90–1.00 mm.

Color ( Fig. 3 ): Almost reddish, base of elytra and pronotum, most of apical half of elytra and outlines of sutures on underside black. Antennae, palpi and legs reddish. Two large basal elytral marks forming one band and extending to sides and suture suture, and two apical spots of elytra pale reddish. Ventral surface except epipleura reddish.

Sculpture: Head anterior to dorsal impression with deep punctures separated by a distance about 2 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 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 denser, surface somewhat uneven especially near middle where punctures are larger, near tip they are fine. Apical half 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 base 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 and cordiform, base same width as head. Basal half flat, anterior part curved down, especially near projecting anterior angles where there is 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, one large deep depression just behind centre of pronotum and of same size and form as longitudinal impressions, 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 the major impressions. Scutellum almost invisible, very short and broad.

Elytra together elongate-oval with point of maximum width near middle, sides slightly converging basally; disc of each elytron with a medial and a sublateral, broad, longitudinal but poorly defined shallow groove containing a row of large shallow 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 as in C. andreas and C. mubboonus but metacoxal lines more strongly raised, very widely separated, subparallel in anterior and posterior quarters, rapidly diverging in middle. Metasternum with a raised line from inside of metacoxal line to inside of mesocoxa. Metacoxal process very flat, distally hardly sinuous, indistinctly notched in middle.

Legs long as in C. andreas and C. mubboonus but mesotibia of male with subapical tooth.

Male: Antenna not broadened, antennomeres 11 fusiform and a bit longer than in female. 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 with well developed 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 in ventral aspect ( Fig. 24 ) with apical lobes blunt and broadly rounded, in lateral aspect ( Fig. 25 ) with apex elongate and ligulate.

Female: Metatibia with a small group of natatorial setae arising in basal half of mesal face and mesotibia without subapical tooth. Females are a little broader, more parallel sided and a bit smaller than males. Measurements: TL = 2.25–2.30 mm, TL-H = 2.0– 2.05 mm, MW = 0.90–1.00 mm.

Differential diagnosis: A distinct species which can easily be separated from the other maculate species of the genus ( C. andreas , C. innae sp.n., C. storeyi sp.n. and C. turaki sp.n.) by the shape and size of body ( Fig. 3 ), the broad but poorly defined elytral striae reaching beyond middle, and the presence of a well developed subapical tooth on the inner edge of male mesotibia. Furthermore, C. plicatus can be distinguished from all other species of the genus by the form of median lobe of the aedeagus ( Figs 24, 25 ).

Distribution: Southern Queensland around Brisbane and in the New England Range of northern New South Wales ( Fig. 28 ). Mainly known from historical specimens collected in the 30’s of the last century in the North Pine River north of Brisbane.

Habitat: A rheophilic species but nothing more is known about its life habits. Nowadays the North Pine River at Petrie and many other rivers in the area are dammed or irrigated and no suitable habitat for Carabhydrus have been found by the authors during several visits to the region in the past two decades. Most probably extinct at the type locality. The Wollomombi River is a headstream of the Macleay River with good riffle habitats with cobble and boulder substratum in some areas, and in many parts still fringed by old growth riverine forest.

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 20–27. Median lobe of aedeagus in ventral and lateral view (scale bar 0.2 mm): 20, 21–Carabhydrus mubboonus; 22, 23—C. niger; 24, 25—C. plicatus; 26, 27—C. storeyi sp.n.

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