Gibbidessus chipi Watts, 1978

Hendrich, Lars, Watts, Chris H. S. & Balke, Michael, 2020, The " minute diving beetles " of southern Australia - taxonomic revision of Gibbidessus Watts, 1978, with description of six new species (Coleoptera, Dytiscidae, Bidessini), ZooKeys 975, pp. 11-49 : 11

Gibbidessus chipi Watts, 1978 Figs 2 , 15 , 22

Gibbidessus chipi Watts, 1978: 33 (original description); Watts (1985: 24, checklist); Lawrence et al. (1987: 335, catalogue); Biström (1988: 19, systematics); Watts (2002: 31, 44, identification key, checklist); Davies et al. (2003: 24, 27, faunistics); Nilsson & Hájek (2020: 108, catalogue).

Type locality.

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

Type material.

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).

Additional material studied

(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).

Diagnosis.

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 ).

Measurements.

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 ).

Affinities.

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 ).

Distribution.

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 ).

Habitat.

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.

Figures

Figures 1 - 4. Habitus of 1 Gibbidessus atomus sp. nov. 2 G. chipi, 3 G. davidi, male 4 G. davidi female. Scale bar: 1.0 mm.

Figures 14, 15. 14 Gibbidessus atomus sp. nov. 15 G. chipi A median lobe in ventral view B median lobe in lateral view, left side C left paramere in lateral view. Scale bar: 0.2 mm.

Figures 22, 23. Distribution of 22 Gibbidessus chipi (black dots), G. drikdrikensis sp. nov. (yellow square), G. kangarooensis sp. nov. (red square) 23 G. atomus sp. nov. (red square), G. davidi sp. nov. (yellow square).

Figures 16, 17. 16 Gibbidessus davidi sp. nov. 17 G. drikdrikensis sp. nov. A median lobe in ventral view B median lobe in lateral view, left side C left paramere in lateral view, D right paramere in lateral view. Scale bar: 0.2 mm.