Carabhydrus mubboonus Larson & Storey, 1994

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 : 14-16

Carabhydrus mubboonus Larson & Storey, 1994

( Figs 7 , 20, 21 , 29 )

Carabhydrus mubboonus Larson & Storey, 1994: 895 ; Larson (1997: 272, 274, 284); Nilsson (2001: 144); Watts (2002: 32, 44).

Type locality: Sandy rainforest stream, 30 km N of Mt. Molloy, Northern Queensland .

Type material: Holotype. Male : “ Australia, Qld., Mt. Lewis Rd. km 17, sandy cr., Nov. 1/90, Larson ” [locality approximately 30 km N Mt. Molloy]”, “ HOLOTYPE Carabhydrus mubboonus Larson & Storey ” [red printed label] ( ANIC) . Paratypes: 5 exs., “ Australia, QLD. Windsor Tableland access rd km 40 Nov. 12/ 90 Larson ”, “ PARATYPE Carabhydrus mubboonus Larson & Storey ” [blue printed label] ( BMNH) .

Additional material studied (5 specimens): Queensland: 1 ex., Northern Queensland, Atherton Tableland, Kauri Creek , rainforest, 20.XI.1998, F. Pederzani leg. ( CLH); 4 exs. northern Queensland, 40 km up Windsor Tableland Road , 12.XI.1990, R. Storey, S. DeFaveri & K. Halfpapp leg. ( CLH) .

Re-descriptions: Measurements: TL = 2.25–2.60 mm; TL–H = 2.05–2.35 mm; MW = 1.00– 1.10 mm.

Color ( Fig. 7 ): Reddish black to almost black except anterior margin of clypeus, mouthparts, ventral surface of head and thorax, and basal and apical margins of sterna 4–6, rufous. Antennae and palpi pale yellowish brown, without infuscation. Legs dark brown to piceous, palest on pro- and mesocoxa, trochanters, base and apex of femora and tibiae, and pro- and mesotarsi.

Sculpture: Head anterior to dorsal impression with deep punctures separated by a distance about equal to their own diameters, and a few sparse, minute punctures; interspaces smooth and shiny without microreticulation except frontal foveae coarsely reticulate and anterior margin of clypeus with transverse lines; head posterior to transverse impression with coarse punctures medially and laterally posteriad to eyes.

Pronotum with coarse punctures and about equally numerous but less conspicuous fine punctures; surface irregularly rugose with punctures somewhat more crowded along troughs of rugae; disc anterolaterally at base of front angle rugose with several coarse setiferous punctures; microreticulation absent.

Elytron with dual punctation similar to that of pronotum but less dense, at least basally; interspaces smooth medially and basally but apex with evident microreticulation, restricted to extreme apex of elytron in male, covering apical quarter in female; epipleuron 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 broad, 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; ventral surface lacking a crease behind eye; maxillary and labial palpi each with apical palpomere fusiform.

Pronotum in dorsal aspect cordiform with point of maximum width at about anterior third of length, 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 the 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; mesal groove beginning approximately opposite basolateral impression of pronotum, sharply defined on basal two-thirds, becoming shallower apically; sublateral groove starting slightly mesad of humeral angle, slightly narrower and shallower than mesal groove, well defined on basal half to two-thirds, obsolete apically. According to Larson & Storey (1994) hind wings reduced to a very small stub.

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 in ventral aspect spatulate, flattened except for a slight median convexity, ovate and bluntly pointed apically, contacting anteromedial lobe of metasternum. Metasternum with a pair of posteriorly diverging carinae arising on anteromedial lobe; and on each side a lateral carina arising posteriad to distal margin of mesocoxal cavity; these two carinae converging posteriorly and approximately contiguous with anterior portion of strongly elevated metacoxal carina. Metasternal wing strongly narrowed laterally, disappearing near anterior angle of metacoxal plate and broadly separated from epipleuron by a suture. Metacoxa with line broad and deep, delimited laterally by strongly developed carina, lines slightly sinuate but more or less evenly diverging anteriorly, posteriorly line ending at base of very small, acute projection over base of metatrochanter; metacoxae medially with hind margin between bases of hind legs conjointly emarginate and recessed to lie in same plane as adjacent abdominal sternite; metacoxal fossae separated by a distance subequal to length of metatrochanter.

Legs relatively large. Profemur with anteroventral margin slightly emarginate subapically and fringed with a row of short, stout setae. Protibia broadened apically, inner margin fringed with a longitudinal row of short setae. 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 (face bearing apical spurs) in both sexes, present on mesal face but differing in degree of development between sexes, longer metatibial spur about two-thirds length metatarsomere 1; metatarsomeres elongate; metatarsal claws equal.

Male: Antenna broadened, antennomeres 5–7 slightly and progressively widened, 8–10 about as wide as long, and 11 fusiform. Profemur with anteroventral margin bearing four basal and a medial, short, stout spines. Protibia with mesal margin bearing a low, obtuse, subapical tooth and a basal row of short, pale setae. Protarsomeres 1–3 slightly dilated, tarsomere 1 with a pair of large oval scales in addition to numerous small adhesive setae. Mesofemur clavate, ventral margin flattened and bearing a brush of elongate golden setae; mesotibia with inner margin bearing an obtuse subapical tooth. Metatibia with basal natatorial setae of mesal face elaborated into a brush of long, yellow setae. Paramere sclerotized, broad, ovate, much shorter than aedeagus, glabrous except for a long apical seta; aedeagus ( Figs 20, 21 ) in ventral aspect with apex bilobed, narrowly emarginate medially, with two sets of lateral flanges and a subapical medial ridge, dorsal surface with a short longitudinal ridge near middle of shaft.

Female: Metatibia with a small group of natatorial setae arising in basal half of mesal face. Measurements: TL = 2.50–2.60 mm, TL-H = 2.25–2.30 mm, MW = 1.00– 1.10 mm.

Differential diagnosis: In size and shape C. mubboonus is close to C. monteithi although the latter has a narrower appearance due to the pronotum being more strongly sinuate laterally with the lateral margins more or less parallel before the right-angled hind angles. Specimens of C. mubboonus have the elytral grooves deeper and broader and the mesal groove extending almost to the elytral apex whereas in C. monteithi it is very shallow in the apical third and discontinuous before the apex. In lateral aspect the aedeagus of C. monteithi ( Fig. 19 ) has a pair of medial spines on the ventral margin, which are lacking in C. mubboonus ( Fig. 21 ).

Distribution: North-eastern Queensland, Atherton and Windsor Tablelands ( Fig. 29 ) ( Larson & Storey 1994).

Habitat: Larson & Storey (1994) gave a very detailed description of the life habitat of the species which will be cited here: “All specimens were collected from small streams in closed-canopy, vine forests. The beetles were constantly associated with clean, coarse granite sand. A few specimens were collected from the edges of sand bars or small embayments in high-gradient, turbulent streams. However, all long series were found in low-gradient stream sections where the substrate was entirely coarse sand and wood yet the current was strong enough to clean the sand of silt and leaves. In this habitat the beetles were found in areas of slow, laminar flow, generally along the inside edge of curved pools and runs. Few specimens were observed moving around in the stream, almost all were captured by disturbing the sand then vigorously sweeping the area with a stout aquatic net. Apparently the beetles were in the surface layer of the sand. In a collecting pan, the insects seldom swim but rather scramble over the bottom and move within the interstitial spaces of the sand. Searches were made for larvae but none was found in the period October to February or in May so that the period of breeding is not known”.

Figures

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).

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.

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.