Gibbidessus chipi Watts, 1978.

Very small diving beetles (1.15–1.9 mm). The smallest epigean dytiscids in Australia can be found in this genus. Body oblong-oval or elongate and fairly compactly built. Head with or without cervical line; frontally not bordered. Palpi rather slender, apically very finely bifid, in one species broad. Pronotum with a pair of basal striae. Elytron with a basal stria but without sutural striae. Punctation of elytra does not form rows. Epipleura lack a basal cavity posteriorly limited by a transverse carina. Prosternal process rather elongate, narrow, laterally distinctly marginated and with ventral surface not medially excavated. Prosternal process reaches metaventrite, which is not distinctly depressed posterior to mesocoxae. Metacoxal lines comparatively short, only slightly longer than distance between them posteriorly. Very fine punctures on either side of midline of metaventrite, not forming distinct rows. Metatrochanters and metafemora not distinctly modified (Biström 1988; Hendrich et al. 2019). Parameres symmetric. Larvae unknown.

Gibbidessus was described as a monotypic genus to accommodate G. chipi Watts, 1978. A molecular phylogenetic investigation covering all Australian Bidessini genera (Hendrich et al. 2010) recovered G. chipi, the single Uvarus species reported from Australia, Uvarus pictipes (Lea, 1899), as well as three undescribed species in one clade (Fig. 26). We refer to this clade as genus Gibbidessus. Subsequently, we assembled a multigene dataset of global Hydroporinae (Balke, work in progress), where we again recovered Gibbidessus species as well as Uvarus pictipes in one clade. The non-Australian Uvarus included in that preliminary study did form a separate, not closely related clade. Consequently, Uvarus pictipes is transferred to Gibbidessus here.

Western Australia, Windy Harbour Road, 11 km south of Northcliffe, small pool in sedge swamp [34°48'51S, 116°4'8E].

Holotype, male: “Australia: SW WA, D´Entrecasteaux NP, 11 km S, Northcliffe, 77m, 4.I.2007, 34.44.048S, 116.05.354E [34°44'0S, 116°5'13E], L. & E. Hendrich (WA 162)”, “Holotype Gibbidessus atomus Hendrich, Watts & Balke des. 2020” [red printed label] (WAM). Paratypes (20 exs.). 7 specimens with same data as holotype, three specimens with “DNA M. Balke 1729”, “DNA M. Balke 2780”, “DNA M. Balke 2781” [green printed labels]; 13 exs., “AUSTRALIA/WA: D´Entrecasteaux N.P., 11 km south of Northcliffe, Windy Harbour Road, 50 m, 3.1.2000, 34°42'S, 116°05'E [34°44'0S, 116°5'13E], Hendrich leg. (loc. WA 10c/156)” (ANIC, CLH, SAMA, ZSM). All paratypes with red printed paratype labels.

1 ex., “Australia, WA, RVDLE03 Riverdale Wetland [32°59'22S, 115°47'7E], 23/09/2008, South West Catchment Council Mon.” (DPAW).

Very small species, externally characterised by widely rounded body, with less pronounced habitus disruption between pronotum and elytron, shiny non-microreticulate dorsal surface and vague ferruginous markings on elytra. Dorsoventrally rather domed. Cervical line present (Fig. 1).

Holotype: TL = 1.15 mm, TL-H = 1.05 mm, MW = 0.6 mm. Paratypes: TL = 1.15–1.30 mm, TL-H = 1.0–1.05 mm, MW = 0.6–0.65 mm.

Head: Dark brown, around eyes almost black. Cervical line present. Strongly and coarsely punctate, rather shiny, microsculpture almost absent. Punctures weakly distributed anteriorly, strong posteriorly between eyes. Antennae relatively short, stout. Antennomeres ferruginous, darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Disc of pronotum somewhat darkened, broadest at posterior corners. Punctation very weakly, almost evenly distributed, shiny, microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra less pronounced, basal pronotal plicae present. Striae moderately defined, on almost 1/2 length of pronotum, moderately incurved.

Elytra: Dark brown with vague basal area ferruginous (Fig. 1). Coarsely and densely punctate, shiny, microsculpture absent. Striae weakly impressed, slightly straighter but shorter than basal pronotal striae.

Ventral side: Ferruginous. Prothorax and apex of abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron ferruginous, coarsely punctate, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibiae and meta-/mesotarsi set in black.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 1). Median lobe of aedeagus as in Fig. 14A, B. Shape of median lobe fairly uniform, bent evenly, apex straight and pointed. Paramere, as in Limbodessus Guignot, 1939, with hook or bent finger-like apical part with tiny setae on tip (Fig. 14C).

This species is similar to G. davidi sp. nov. but readily separated by its smaller size, the different colour pattern and the form of the median lobe and parameres (Figs 14, 16).

From Latin atomus (smallest particle), as it is the smallest epigean diving beetle in Australia described so far.

South-western Australia. Known only from the type locality in the D´Entrecasteaux National Park, south of Northcliffe and the Riverdale Wetland [32°59'22S, 115°47'7E] (Fig. 23).

Most specimens were obtained from an exposed, shallow and small roundish puddle without any vegetation, except some algae (Fig. 27B). The remaining specimens were collected in a half-shaded pool in a Melaleuca blackwater swamp (Fig. 27A), with few clumps of Juncus spp. and extensive beds of macrophytes; depth up to 20 cm; bottom of sedge-filled peat (pH 5.5), twigs and rotten leaves. The heathlands south of Northcliffe are seasonally flooded, with some permanent water bodies in the summer. At Northcliffe the species is syntopic with G. davidi sp. nov. (Hendrich 2001a), at the Riverdale Wetland it was collected with G. davidi sp. nov. and G. rottnestensis sp. nov.

Apart from the Gibbidessus, the water beetle coenosis at Northcliffe included the following species: Dytiscidae: Limbodessus inornatus (Sharp, 1882), Antiporus hollingsworthi Watts, 1997, A. mcraeae Watts & Pinder, 2000, Brancuporus gottwaldi (Hendrich, 2001), Sternopriscus minimus Lea, 1899, S. eikei Hendrich & Watts, 2007, Exocelina ater (Sharp, 1882); Hydrophilidae: Enochrus eyrensis (Blackburn, 1895), Limnoxenus zealandicus (Broun, 1880), Paracymus pygmaeus (Macleay, 1871).

Australia, New South Wales, Collector, old farm dam [34°54'40S, 149°26'24E].

Holotype, male [with one paratype on the same plate]: “Collector NSW Febr 1961 C.W.”, “Holotype” [red printed label], “ANIC Database No. 25 015140” [printed label], “Holotype Gibbidessus chipi Det. C. Watts 1976 [handwritten label by Chris Watts] (ANIC). Paratypes (10 exs.). 2 males, 4 females: “Collector NSW 2/61” [handwritten label by Chris Watts], “Paratype Gibbidessus chipi Det C. Watts 1976” [white, printed and handwritten label], “ANIC Database No 2515141” (ANIC); 2 males: “Collector NSW 2/61” [handwritten label by Chris Watts], “Paratype Gibbidessus chipi Det C. Watts 1976” [white, printed and handwritten label], “SAMA Database No 25-003994” (SAMA); 1 male, 1 female: “Dartmoor Victoria Jan 59. CW” [handwritten label], “Paratype Gibbidessus chipi Det C. Watts 1976” [white, printed and handwritten label], “SAMA Database No 25-003398” (SAMA).

(17 exs.): South Australia. 2 exs., “1 km S, Nangwarry 5.X.2000, C. Watts leg.”, “SAMA Database No 25-004002”, one specimen “DNA M. Balke 2109 [green printed label] (SAMA, ZSM); 3 exs., “Fleurieu Peninsula, Myponga, A.H. Elston leg.”, “SAMA Database No 25-00399” (SAMA); 1 ex., “Mt. Crawford State Forest, Watts Gully, 3.X.1998, C. Watts leg.”, “SAMA Database No 25-003996” (SAMA). Victoria: 1 ex., “5.3 km S, Drik Drik,14.VIII.2004, C. Watts leg.”, “DNA Voucher d” (SAMA); 6 exs., “18 km W Casterton, 25.IX.1998, C. Watts leg.”, “SAMA Database No 25-004003” (SAMA); 3 exs., “18 km W Casterton, 25.IX.1998, C. Watts leg.” (CLH); 1 ex., “22 km W Casterton, 23.IX.1999, C. Watts leg.”, “photographed” [yellow label], “SAMA Database No 25-004004” (SAMA).

Medium-sized species which externally is characterised by a widely rounded body, shiny non-microreticulate dorsal surface, vague testaceous markings on elytra, and without habitus disruption between pronotum and elytron. Dorsoventrally rather domed. Cervical line present (Fig. 2).

TL = 1.5–1.55 mm, TL-H = 1.4–1.45 mm, MW = 0.86–0.98 mm.

Head: Dark brown, around eyes almost black. Cervical line present. Strongly and coarsely punctate, rather shiny, microsculpture almost absent. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1-2 ferruginous, 3-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Disc of pronotum somewhat darkened, broadest at posterior corners. Punctation very weakly punctate almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra not pronounced, basal pronotal plicae present. Striae well defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Ferruginous, with vague areas darkened (Fig. 2). Coarsely and densely punctate, shiny, microsculpture absent. Striae strongly impressed, same length as basal pronotal striae but slightly straighter.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and fine punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron testaceous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsi set in black.

Male . Dorsal surface with coarse punctures but otherwise with shiny surface Fig. 2. Median lobe of aedeagus as in Fig. 15A, B. Shape of median lobe fairly uniform, apex in lateral view straight and pointed, in ventral view very broad and rounded at apex. Parameres bi-segmented and elongated with few setae at apex (Fig. 15C).

This species is similar to G. drikdrikensis sp. nov. but readily separated by its smaller size, and the form of the median lobe (Figs 15, 17).

South-eastern Australia, from the Lofty Ranges near Adelaide and north-eastern Tasmania to Canberra (Watts 1978). Also recorded from King Island, Bertie Lagoon [39°42'36S, 144°4'24E] (Davies et al. 2003), northwest of Tasmania (Fig. 22).

The type specimens were collected in an old farm dam and its flood zone, overgrown by rich vegetation. In Victoria and South Australia most of the specimens were collected in small shallow pools and seasonal wetlands. A single specimen from South Australia (Mount Crawford State Forest, Watts Gully) has been found in a shallow, slow flowing temporary forest creek. At Dri Drik, in Victoria, the species is syntopic with G. drikdrikensis sp. nov.

Western Australia, Perth, suburb Success, Beeliar Regional Park, shallow peaty puddle [32°8'4S, 115°50'22E].

Holotype, male: “Australia, WA, Perth, Success, Beeliar RP, shallow peaty puddle 32°8'4.97"S, 115°50'22.78"E 21.-31.10.2015 L. Hendrich (WA 1/15)”, “Holotype Gibbidessus davidi Hendrich, Watts & Balke des. 2020” (WAM) [red printed label]. Paratypes (370 exs.). 354 specimens with same data as holotype (ANIC, CGC, CLH, SAMA, WAM, ZSM); 4 exs, “Australia: SW WA, D´Entrecasteaux NP, 11 km S, Northcliffe, 77m, 4.I.2007, 34.44.048S, 116.05.354E [34°44'0S, 116°5'13E], L. & E. Hendrich (WA 162)” (ZSM); 10 exs., “Australia, WA, Albany Hwy, Muir Lakes Nature Reserve, SW part of Byenup Lagoon, 4.& 5.1.2000, 34°30'4S, 116°44'19E, Hendrich leg. (loc. WA 11/157)” (CLH, ZSM); 1 ex., “Australia, WA, Barlee Brook Dickson Road (A) [34°12'17S, 115°46'18E], DON03, 21/10/2005, South West Forest Monitoring” (DPAW); 1 ex., “Australia, WA, Fish Creek (A) [34°37'29S, 116°26'11E], SHA22, 17/10/2010, South West Forest Monitoring” (DPAW); 4 exs., “Australia, WA, RVDLE03 Riverdale Wetland [32°59'23S, 115°47'23E], 23/09/2008, South West Catchment Council Mon.” (DPAW). All paratypes with red printed paratype labels.

Small species which externally is characterised by a wide rounded body, shiny non-microreticulate dorsal surface, vague testaceous markings on elytra, and without habitus disruption between pronotum and elytron. Dorsoventrally rather domed. Cervical line present (Fig. 3).

Holotype: TL = 1.45 mm, TL-H = 1.35 mm, MW = 0.83 mm. Paratypes: TL = 1.35–1.5 mm, TL-H = 1.15–1.4 mm, MW = 0.8–0.9 mm.

Head: Ferruginous, around eyes almost black. Cervical line present (Fig. 12A). Strongly and coarsely punctate, rather shiny, microreticulation present. Punctures weak anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1-8 ferruginous, 9-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Disc of pronotum somewhat darkened, broadest at posterior corners. Punctation of pronotum very weak, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra less pronounced, basal pronotal plicae present. Striae moderately defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Dark brown with vague basolateral area ferruginous (Fig. 3). Coarsely and densely punctate, shiny, microsculpture absent. Striae deeply impressed, straight but shorter than basal pronotal striae.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly not divergent. Epipleuron ferruginous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsi set in black.

Male. Smaller and more elongate than female (Fig. 4). Median lobe of aedeagus as in Fig. 16A, B. Shape of median lobe in lateral view, straight and fairly uniform, in ventral view broad, with a thorn on each side, and rounded at apex. Parameres bi-segmented and elongated with few setae at apex (Fig. 16C, D).

This species is similar to G. atomus sp. nov. but readily separated by its larger size, the different colour pattern and the form of the median lobe and parameres (Figs 14, 16). From G. pederzanii sp. nov. it can be distinguished by the less roundish body and the form of the median lobe and parameres (Figs 16, 19).

The beetle is named after the son of the first author, David Hendrich. The specific epithet is a substantive in the genitive case.

South-western Australia. From Perth in the north to D´Entrecasteaux National Park in the south (Fig. 23).

In the Northcliffe area most specimens were obtained from an exposed, shallow and small roundish puddle, without any vegetation, except some algae. The other specimens were collected in a half-shaded pool in a Melaleuca blackwater swamp, with few clumps of Juncus spp. and extensive beds of macrophytes; depth up to 20 cm; bottom consisted of sedge-filled peat (pH 5.5), twigs and rotten leaves (Figs 27, 28). The whole area south of Northcliffe is seasonally flooded with some permanent central water bodies in summer. In the D´Entrecasteaux NP the species is syntopic with G. atomus sp. nov., and around Perth in the Beeliar Regional Park with G. rottnestensis sp. nov. At the Riverdale Wetland Reserve G. davidi sp. nov. was syntopic with G. atomus sp. nov. and G. rottnestensis sp. nov.

Apart from the Gibbidessus, the water beetle coenosis at Northcliffe included the following species: Dytiscidae: Limbodessus inornatus, Antiporus hollingsworthi, A. mcraeae, Brancuporus gottwaldi, Sternopriscus minimus, S. eikei, Exocelina ater; Hydrophilidae: Enochrus eyrensis, Limnoxenus zealandicus, Paracymus pygmaeus (see Hendrich 2001a). In the Beeliar Park the two Gibbidessus species share their habitat with Limbodessus inornatus, Paroster insculptilis (Clark, 1862), Exocelina ater, Rhantus suturalis (Macleay, 1825) and Rhantus simulans Régimbart, 1908.

Australia, Victoria, Drik Drik, old farm dam [37°59'27S, 141°17'18E].

Holotype: Male, “1 km S, Drik Drik Vic. 24/9/98 C. Watts”, “Photographed”, “SAMA Database No 25-004000”, “Holotype Gibbidessus drikdrikensis sp.nov. Hendrich, Watts & Balke des. 2020” [red printed label] (SAMA). Paratypes (6 exs.): 6 specimens with same data as holotype. Two specimens with “DNA voucher b” and “DNA voucher c” and one with a yellow prointed label “photographed” (CLH, SAMA). All paratypes are provided with printed red paratype labels.

Medium-sized species which externally is characterised by a wide rounded body, shiny non-microreticulate dorsal surface, vague testaceous markings on elytra, and without slight habitus disruption between pronotum and elytron. Dorsoventrally rather domed. Cervical line present (Fig. 5).

Holotype: TL = 1.7 mm, TL-H = 1.5 mm, MW = 0.98 mm. Paratypes: TL = 1.6–1.7 mm, TL-H = 1.4–1.5 mm, MW = 0.86–0.98 mm.

Head: Dark brown, around eyes almost black. Cervical line present. Strongly and coarsely punctate, rather shiny, microsculpture almost absent. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1 and 2 ferruginous, 3-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Disc of pronotum somewhat darkened, broadest at posterior corners. Punctation very weak, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra not pronounced, basal pronotal plicae present. Striae well defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Ferruginous, with vague areas darkened (Fig. 5). Coarsely and densely punctate, shiny, microsculpture absent. Striae strongly impressed, same length as basal pronotal striae but slightly straighter.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron testaceous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous meta-/mesotarsi set in black.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 5). Median lobe of aedeagus as in Fig. 17A, B. Shape of median lobe fairly uniform, evenly bent in lateral view, apex straight and pointed at tip in ventral view. Parameres bi-segmented, broad and with few setae at apex (Fig. 17C, D).

This species is very similar to G. chipi but readily separated by its larger size and the form of the median lobe and parameres (Figs 15, 17).

The species is named after the type locality. The specific epithet is a substantive in the genitive case.

Only known from the type locality Drik Drik in south-western Victoria (Fig. 22).

The few specimens were collected in shallow water at the edge of a large, exposed but shallow farm dam, overgrown with grasses and sedges. The species is syntopic with G. chipi.

South Australia, Kangaroo Island, Eleaner River at South Coast [Road] Crossing, edge sample [35°56'S, 137°14'E].

Holotype: Male, “Eleaner R. S, Coast rd AWQ [Australian Water Quality] survey 8/11/95 site 3714 [35°56'S, 137°14'E]” “Holotype Gibbidessus kangarooensis sp. nov. Hendrich, Watts & Balke des. 2020” [red printed label] (SAMA).

Small species which externally is characterised by a more elongate body, shiny non-microreticulate dorsal surface, and with well pronounced habitus disruption between pronotum and elytron. Dorsoventrally rather flattened. Without cervical line but rather a few punctures instead (Fig. 6).

Holotype: TL = 1.55 mm, TL-H = 1.4 mm, MW = 0.88 mm.

Head: Ferruginous, without cervical line but rather a few punctures instead. Evenly and coarsely punctate, shiny, microsculpture absent. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae missing.

Pronotum: Ferruginous, anterior and posterior margins darker, broadest at middle. Punctation weak anteriorly but quite strong on posterior half and on lateral sides, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum broadly margined and almost evenly rounded. Angle between pronotum and elytra well pronounced, basal pronotal and elytral plicae present. Striae moderately defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Dark brown with vague basal area ferruginous (Fig. 6). Coarsely and densely punctate, shiny, microsculpture absent. Striae weakly impressed, slightly straighter and of same length as basal pronotal striae.

Ventral side: Ferruginous. Prothorax and apex of abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron ferruginous, coarsely punctate, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsi somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 6). Median lobe of aedeagus as in Fig. 18A, B. Shape of median lobe, bent evenly and fairly uniform in lateral view, in ventral view pointed at apex. Parameres bi-segmented, elongated, and with few setae at apex (Fig. 18C, D).

Female. Unknown.

This species is similar to G. pictipes but readily separated by the different colour pattern and the more flattened body. Furthermore, both species can be separated by the form of the median lobe and parameres (Figs 18, 20).

The species is named after the type locality. The specific epithet is a substantive in the genitive case.

A rare species, only known from the type locality on Kangaroo Island, South Australia (Fig. 22).

The single specimen was collected at the edge of the Eleaner River in the southern part of Kangaroo Island. Most probably this is not the original habitat of the species. Almost all Gibbidessus inhabit more seasonal, open wetlands, overgrown with sedges and rushes.

Australia, Western Australia, creek around Nannup [33°58'S, 115°45'E].

Holotype: Male, “Australia (WA) Nannup env. roadside creeks 1/12/98 Pederzani”, “Holotype Gibbidessus pederzanii Hendrich, Watts & Balke des. 2020” [red printed label] (SAMA). Paratypes (13 exs.): All specimens with same data as holotype. Two specimens with “SAMA Database No 25-001593” and one with a yellow printed label “photographed” (CFP, CLH, SAMA, ZSM). All paratypes are provided with printed red paratype labels.

Medium-sized species which externally is characterised by a rounded habitus, without disruption between pronotum and elytron, and shiny, non-microreticulate dorsal surface with testaceous markings on elytra. Dorsoventrally rather arched. Without cervical line but rather a few punctures instead (Fig. 7).

Holotype: TL = 1.5 mm, TL-H = 1.3 mm, MW = 0.85 mm. Paratypes: TL = 1.5–1.6 mm, TL-H = 1.3–1.4 mm, MW = 0.85–0.95 mm.

Head: Ferruginous, around eyes almost black, without cervical line but rather a few punctures instead (Fig. 12B). Coarsely punctate, rather shiny, weak microreticulation visible. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1 and 2 ferruginous, 3-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins, between striae, slightly darker, broadest at posterior corners. Punctation very weak almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra less pronounced, basal pronotal plicae present. Striae moderately defined, almost 1/2 length of pronotum, slightly incurved.

Elytra: Dark brown with vague basolateral and apical area ferruginous (Fig. 7). Coarsely and densely punctate, shiny, microsculpture absent. Striae deeply impressed, straight but shorter than basal pronotal striae.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly not divergent. Epipleuron testaceous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous with meta- and mesotarsi somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 7). Median lobe of aedeagus as in Fig. 19A, B. Shape of median lobe, almost straight and fairly uniform in lateral view, in ventral view rounded at apex. Parameres bi-segmented, elongated, and without setae at apex (Fig. 19C, D).

This species is similar to G. davidi sp. nov. but readily separated by the different colour pattern, the more roundish body (Figs 4, 7), the larger punctation on elytra, and the form of the median lobe and parameres (Figs 16, 19).

The species is named after our colleague, the dytiscid specialist Fernando Pederzani (Ravenna, Italy), who collected the type material. The specific epithet is a substantive in the genitive case.

South-western Australia. A rare species, which is only known from the type locality somewhere around Nannup in south-western Australia. Most probably a more inland species and restricted to forested areas and not in heathland or coastal sedge swamps (Fig. 25).

All specimens were collected in shallow water at the edge of a small slow flowing forest creek (F. Pederzani in litt.).

Australia, south-western Australia, Pinjarrah [32°37'56S, 115°51'49E].

Syntype, female, “pictipes Lea Type Pinjarrah” (handwritten label), “Bidessus pictipes Lea W. Australia TYPE” (handwritten label), “SAMA Database No 25-001599” (SAMA).

(320 exs.). 51 exs., “WA Lake Nalyerin 33 08S, 116 22E CHS, Watts 6/10/03”, “SAMA Database 25-009282” (SAMA); 4 exs., “Nalyeen Lake [Nalyerin] WA J. McRae 8/10/97”, “SAMA Database No 25-002918” (SAMA); 1 ex., “WA Byenup Lagoon NR 21/9/00 C.H.S. Watts” “SAMA Database No 25-002922” (SAMA). 2 exs., “Australia, WA, SWA31 (A), Helena River, 22/08/2005, South-west Forest Monitoring” (DPAW); 1 ex., “Australia, WA, HAR21 (A), Stirling Dam 2, 7/09/2006, South-west Forest Monitoring” (DPAW); 3 exs., “Australia, WA, SPM011 (B) Kulicup Swamp, 6/11/1998, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 1 ex., “Australia, WA, SPM011 (A) Kulicup Swamp [34°20'1S, 116°47'17E], 23/10/2002, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 1 ex., “Australia, WA, SPM011 (B) Kulicup Swamp [34°20'1S, 116°47'17E], 23/10/2002, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 2 exs., “Australia, WA, SPM011 (A) Kulicup Swamp [34°20'1S, 116°47'17E], 11/10/2000, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 2 exs., “Australia, WA, SPM011 (B) Kulicup Swamp [34°20'1S, 116°47'17E], 11/10/2000, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 1 ex., “Australia, WA, SPM024 (A) Lake Pleasant View [34°49'S, 118°10'E], 24/10/1999, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 3 exs., “Australia, WA, SPM024 (A) Lake Pleasant View [34°49'S, 118°10'E], 24/10/2003, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 2 ex., “Australia, WA, SPM024 (B) Lake Pleasant View [34°49'S, 118°10'E], 24/10/2001, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 4 exs., “Australia, WA, SPM024 (A) Lake Pleasant View [34°49'S, 118°10'E], 24/10/1999, Salinity Action Plan Wetland Monitoring Programme” (DPAW); 1 ex., “Australia, WA, RUAB01 (A) Ruabon Road 01 [33°37'S, 115°27'E], 11/10/2007, South-west Catchment Council Wetland monitoring” (DPAW); 1 ex., “Australia, WA, RVDLE03 (A) Riverdale 03 [32°59S, 115°47E], 4/10/2007, South-west Catchment Council Wetland monitoring” (DPAW); 30 exs., “Australia, WA, SPS111 (A), Boyacup Bridge Swamp [34°13'S, 117°15'E], 10/10/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 1 ex., “Australia, WA, SPS032 (A), Qualeup Lake [33°50'S, 116°45'E], 9/10/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 2 exs., “Australia, WA, SPS103 (A), Lake Poorginup [34°32'S, 116°44'E], 2/10/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 4 exs., “Australia, WA, SPS104 (A), Pindicup Lake [34°25'S, 116°43'E], 2/10/1998, Salinity Action Plan Wetland Biological Survey”, one specimen “M. Balke DNA 7250” [green printed label] (DPAW, ZSM); 1 ex., “Australia, WA, MUB030 (A), Pindicup Lake [34°25'S, 116°43'E], 25.09.2014, Muir-Byenup Survey” (DPAW); 11 exs., “Australia, WA, MUB030 (A), Pindicup Lake, 25.09.2014, Muir-Byenup Survey (DPAW); 4 exs., “Australia, WA, SPS105 (A) Kodjinup Melaleuca Swamp [34°23'S, 116°39'E], 2/10/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 30 exs, “Australia, WA, SPS108 (A) Pillenorup Swamp, 30/09/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 7 exs., “Australia, WA, SPS113 (A) Tucker’s Road Melaleuca Swamp, 27/08/1998, Salinity Action Plan Wetland Biological Survey” (DPAW); 1 ex., “Australia, WA, LVR003 (A) Lower Vasse River Site 3, 4/10/2001, Lower Vasse River Clean-up Program” (DPAW); 1 ex., “Australia, WA, LVR004 (A), Lower Vasse River Site 4, 5/10/2001, Lower Vasse River Clean-up Program” (DPAW); 1 ex., “Australia, WA, LVR005 (A), Lower Vasse River Site 5, 5/10/2001, Lower Vasse River Clean-up Program” (DPAW); 6 exs., “Australia, WA, JCS019 (A), Sedge Swamp W of Deadhorse Soak [29°54'7S, 115°1'11E], 21/09/2011, Jurien Coastal Survey” (DPAW); 1 ex., “Australia, WA, Mulgarnup MUB 012, 28.01.2004, Andrew Storey leg.” (DPAW); 2 exs., “Australia, WA, Mulgarnup MUB 012, 1.10.2014, M. Pennifold leg.”, two specimens “M. Balke DNA 7252”, “M. Balke DNA 7253” [green printed labels] (ZSM); 4 exs., “Australia, WA, W Kodjinup #18 [34°23'S, 116°39'E], 28.01.2004, Andrew Storey leg.” (DPAW); 1 ex., “Australia, WA, Wimbalup #52 [34°29'S, 116°50'E], 29.11.2003, Andrew Storey leg.” (DPAW); 11 exs., “Australia, WA, MUB019 (A), Galamup Swamp [34°26'S, 116°45'E], 30.09.2014, Muir-Byenup Survey”, one specimen “M. Balke DNA 7262” [green printed label] (DPAW, ZSM); 23 exs., “Australia, WA, MUB035, NE Unicup NR [34°20'S, 116°43'E], 24.09.2014, Muir-Byenup Survey”, one specimen “M. Balke DNA 7257” [green printed label] (DPAW, ZSM); 43 exs., “Australia, WA, MUB037 (A) S, Kulunilup NR [34°20'S, 116°47'E], 25.09.2014, Muir-Byenup Survey”, three specimens “M. Balke DNA 7259”, “M. Balke DNA 7260”, “M. Balke DNA 7261” [green printed labels] (DPAW, ZSM); 11 exs., “Australia, WA, MUB011 (A) Kulunilup Lake [34°20'S, 116°47'E], 25.09.2014, Muir-Byenup Survey” (DPAW); 2 exs., “Australia, WA, MUB008 (B) Noobijup Swamp [34°23'S, 116°47'E], 24.09.2014, Muir-Byenup Survey” two specimens “M.Balke DNA 7254”, “M. Balke DNA 7255” [green printed labels] (DPAW, ZSM); 1 ex., “Australia, WA, MUB005 (A), Yarnup Swamp [34°22'26S, 116°52'4E], 22.09.2014, Muir-Byenup Survey” (DPAW); 12 exs., “Australia, WA, MUB012 (A), Mulgarnup Swamp [34°15'1S, 116°41'44E], 01.10.2014, Muir-Byenup Survey” (DPAW); 1 ex., “Australia, WA, Twin Swamps NW [31°43'7S, 116°0'50E], 24/09/1992, Twin Swamps/Ellen Brook Survey” (DPAW); 1 ex., “Australia, WA, SPS031, 08/10/1997, SAP Survey” (DPAW); 1 ex., “Australia, WA, ABP041, 14/09/2007, Avon Baselining Project” (DPAW); 26 exs., “Australia, WA, Albany Hwy, Muir Lakes Nature Reserve, SW part of Byenup Lagoon, 4.& 5.1.2000, 34°29'S, 116°44'E, Hendrich leg. (loc. WA 11/157)” (CLH, ZSM); 18 ex., “Australia, WA, Albany, 3 km ENE Manypeaks, Lake Pleasant Nature Reserve, 7.1.2000, 34°49'S, 118°10'E, Hendrich leg. (loc. WA 13/159) (CLH, ZSM); 38 exs., “Australia, WA, Darling Range, Lane Poole Conservation Reserve, Nalyerin Lake, 300 m, 29. & 30.12.1999, 33°8.51'S, 116°22.15'E, Hendrich leg. (loc. WA 4/151)” (CGC, CLH, ZSM); 1 ex., “Australia: SW WA, 3 km NE Manypeaks, Lake Pleasant View NR, 91m, 2.I.2007, 34°49'S, 118°10'E, L. & E. Hendrich leg. (WA 160)” (ZSM).

Watts (1978), who moved Bidessus pictipes to Uvarus, already noticed that this species might not belong to Uvarus: “It is with considerable hesitation that I place the following species in this genus. I suspect that it will eventually prove to belong to a genus of its own”.

Small and dark brown species, with vague testaceous markings on elytra, and with habitus disruption between pronotum and elytron. Dorsoventrally rather flattened. Head without cervical line but rather a few punctures instead (punctures not obvious in females) (Fig. 8).

Measurements: Lectotype, female: TL = 1.45 mm, TL-H = 1.25 mm, MW = 0.82 mm. Additional material: TL = 1.45–1.6 mm, TL-H = 1.3–1.4 mm, MW = 0.8–0.83 mm.

Head: Dark brown to ferruginous, without cervical line but rather a few punctures instead (punctures not obvious in females) (Fig. 13A). Evenly and coarsely punctate, shiny but with weak microreticulation. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1–3 ferruginous, 4–11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker, broadest at middle. Punctation very weak, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra well pronounced, basal pronotal plicae present. Striae moderately defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Dark brown with vague basal area ferruginous (Fig. 8). Coarsely and densely punctate, shiny, microsculpture absent. Striae weakly impressed, slightly straighter than in female specimens and of same length as basal pronotal striae.

Ventral side: Ferruginous. Prothorax and apex of abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron ferruginous, coarsely punctate, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsi somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 8). Median lobe of aedeagus as in Fig. 20A, B. Shape of median lobe, bent evenly and fairly uniform in lateral view, in ventral view tapering and pointed at apex. Parameres bi-segmented, elongated, and with setae inside apical hook (Fig. 20C, D).

Female. Dorsal surface almost mat, with coarse punctures and dense microreticulation (Fig. 9).

This species is similar to G. kangarooensis sp. nov. and the larger G. rottnestensis sp. nov. (TL = 1.5–1.7 mm) but readily separated by the different colour pattern. Furthermore, all three species can be separated by the form of their median lobes and parameres (Figs 18, 20, 21).

South-western Australia. The most common and widespread species in south-western Australia and a more inland species. South of a line from 230 km north of Perth (Leeman) to Albany (Fig. 24).

Permanent and seasonal, very shallow, sun exposed or half-shaded sedge swamps, lakeshores, larger ponds and flooded meadows on sandy bottom, with a thin layer of peat or rotten debris of sedges (Figs 30, 31). A winter and early spring breeder. Most specimens were collected in September and October, with the next generation in December and January. Apart from G. pictipes, the water beetle coenosis at Nalyerin Lake (Fig. 31) included the following species: Dytiscidae: Limbodessus inornatus, Antiporus hollingsworthi, Sternopriscus minimus, Exocelina ater; Hydrophilidae: Enochrus eyrensis, Limnoxenus zealandicus, Paracymus pygmaeus (see Hendrich 2001b). At Manypeaks (Fig. 30) G. pictipes was collected with the Dytiscidae: Limbodessus inornatus, Sternopriscus browni Sharp, 1882, S. multimaculatus (Clark, 1862), S. storeyi Hendrich & Watts, 2004, S. wattsi Hendrich & Watts, 2004, Necterosoma darwinii (Babington, 1841), Rhantus suturalis and Lancetes lanceolatus (Clark, 1863).

Australia, south-western Australia, Rottnest Island [32°0'22S, 115°30'26E].

Holotype: Male, “W AUS, ca. 25 km N Augusta on Rd. 250, shallow pool, 4.11.2013, leg. Wewalka (A4)” “Holotype Gibbidessus rottnestensis Hendrich, Watts & Balke des. 2020” [red printed label] (WAM). Paratypes (27 exs.): 4 specimens with same data as holotype (CGW, ZSM); 3 males, 1 female “Rottnest Is. [32°0'22S, 115°30'26E] Oct´ 31 W.A.”, “Australia, Harvard Exp., Darlington”, “Museum of Comparative Zoology”, “ANIC Database No. 25013255” (ANIC); 3 specimens with same data, and “SAMA Database No 25-00/596” (SAMA). 2 exs., “Australia, WA, Perth, Success, Beeliar RP, shallow peaty puddle 32°8'4S, 115°50'22E 21.-31.10.2015 L. Hendrich (WA 1/15)”, “M. Balke 7248”, “M. Balke 7247” [green, printed label] (ZSM); 1 ex., “Australia, WA, Albany Hwy, Muir Lakes Nature Reserve, SW part of Byenup Lagoon, 4. & 5.1.2000, 34°29'S, 116°44'E [34°30'4S, 116°44'19E], Hendrich leg. (loc. WA 11/157)” (CLH); 3 exs., “Australia, WA, 1 km W Kodjinup NP 34°24.03S, 116°38.37E [34°24'1S, 116°38'22E] 4.X.2003, CHS, Watts leg.”, one specimen “M. Balke 3921” [green, printed label] (CLH, SAMA); 1 ex., “WA Kodjinup N.R. [34°23'10S, 116°39'30E] 21/9/00 C.H.S.Watts”, “SAMA Database No 25-00/594” (SAMA); 2 exs., “AUSTRALIA, WA, Midlands, 38 Km ESE Cervantes, Wongonderrah Road, Nambung River Crossing, 9.9.2002, 30°33'21S, 115°21'27E, Hendrich leg. /Loc. 28b/192b” (CLH); 1 ex., “SW Australia/ N Bunbury, Yalgorup N.P. östl. Preston Beach [32°52'35S, 115°40'6E], 0m, 24.11.1996, Hendrich leg./Lok. 30” (CLH); 1 ex., “Australia, WA, RVDLE03 Riverdale Wetland [32°59'22S, 115°47'7E], 23/09/2008, South West Catchment Council Mon.” (DPAW); 1 ex., “Australia, WA, Pindicup Lake [34°24'35S, 116°43'20E], MUB030, 29.09.2014, Muir-Byenup Survey, M. Pennifold leg.” (DPAW); 1 ex., “Australia, WA, Pindicup Lake [34°24'35S, 116°43'20E], MUB030, 25.09.2014, Muir-Byenup Survey, M. Pennifold leg.” (DPAW); 2 ex., “Australia, WA, wetland north of Mialla Lagoon [33°10'04S, 115°44'01E], MIAL01, 8/10/2007, South-west Catchment Council Wetland Monitoring” (DPAW). All paratypes are provided with red printed paratype labels.

Watts (1978: 33) reports Uvarus pictipes from Rottnest Island (housed in Museum of Comparative Zoology and SAMA); these specimens belong to Gibbidessus rottnestensis sp. nov.

Larger species which externally is characterised by a more elongate body, shiny non-microreticulate dorsal surface, testaceous markings on elytra, and with distinct habitus disruption between pronotum and elytron. Dorsoventrally slightly flattened. Without cervical line but rather a few punctures instead (Fig. 10).

Holotype: TL = 1.85 mm, TL-H = 1.65 mm, MW = 0.95 mm. Paratypes: TL = 1.7–1.9 mm, TL-H = 1.5–1.7 mm, MW = 0.85–1.0 mm.

Head: Black to ferruginous, without cervical line but rather a few punctures instead (punctures not obvious in females) (Fig. 13B). Evenly and coarsely punctate, shiny but with weak microreticulation. Punctures weak anteriorly and stronger posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1-3 ferruginous, 4-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Broadest at middle. Punctation very strong, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum broadly margined and almost evenly rounded. Angle between pronotum and elytra well pronounced, basal pronotal plicae present. Striae moderately defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Dark brown to black, with distinct basal and subapical testaceous markings (Fig. 10). Coarsely and densely punctate, shiny, microsculpture absent. Striae weakly impressed, slightly incurved and of same length as basal pronotal striae.

Ventral side: Ferruginous. Prothorax and apex of abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron ferruginous, coarsely punctate, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsae somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 10). Median lobe of aedeagus as in Fig. 21A, B. Shape of median lobe, bent evenly and fairly uniform in lateral view, in ventral view strongly tapering and rounded at apex. Parameres bi-segmented, elongated, without setae inside apical hook (Fig. 21C, D).

Female. Dorsal surface almost mat, with coarse punctures and dense microreticulation (Fig. 11).

This species is similar to the smaller G. pictipes (TL = 1.45–1.6 mm) but readily separated by the different colour pattern on elytra. Furthermore, both species can be separated by the form of their median lobes and parameres (Figs 20, 21).

The species is named after the type locality. The specific epithet is a substantive in the genitive case.

South-western Australia. Widespread but always rare and in low population densities. A more coastal species, from around 100 km north of Perth to south of Augusta and eastwards to the Muir Lakes (Fig. 25).

Seasonal, very shallow and exposed sedge swamps, pool and puddles on sandy bottom, with a thin layer of peat and rotten debris of sedges (Figs 28, 29). Gibbidessus rottnestensis sp. nov. tolerates slightly saline water as it was found at Preston Beach in a shallow lagoon near the coast. According to the data it is an early spring breeder. Most specimens were collected in September and October. In the Riverdale Wetland the species was syntopic with Gibbidessus atomus sp. nov. and G. davidi sp. nov. For the rich water beetle coenosis in Beeliar Regional Park near Perth see under Gibbidessus davidi sp. nov. In the seasonal swamps at Wongonderrah Road, near Nambung River Crossing, the species was collected with several hundred specimens of an undescribed Exocelina species and Hyderodes crassus Sharp, 1882; at Preston Beach north of Bunbury it was collected with Hyphydrus elegans (Montrouzier, 1860), Necterosoma darwinii, and Platynectes aenescens Sharp, 1882.