Sandracottus jaechi Wewalka & Vazirani, 1975

Hendrich, Lars & Brancucci, Michel, 2025, Revision of the Oriental and Australasian diving beetle genus Sandracottus Sharp, 1882 (Coleoptera, Dytiscidae, Dytiscinae), ZooKeys 1223, pp. 87-147 : 87-147

Sandracottus jaechi Wewalka & Vazirani, 1975

Figs 9 , 20 , 29 , 54

Sandracottus jaechi Wewalka & Vazirani, 1975: 114 ( Ceylon [ Sri Lanka], Nuwara Eliya); Ghosh and Nilsson 2012: 18 (cat.); Hájek and Nilsson 2024: 91 (cat.).

Type material.

Holotype: Male: “ Nuwara Eliya , 1800 m, leg. Kruse [ca 1930, Wewalka and Vazirani 1975] Ceylon (Sri Lanka) ”, “ TYPUS Sandracottus jaechi n. sp. Wewalka & Vazirani 82 ” [red label] ( CGW, later in NMW) . Paratypes: 1 female: “ Nuwara Eliya , leg. Kruse 1800 m Ceylon [Sri Lanka] ”, “ Paratypus Sandracottus jaechi n. sp. Wewalka & Vazirani 82 ” [red label] ( NMW) ; 1 female: “ Nuwara Eliya , leg. Kruse 1800 m Ceylon [Sri Lanka] ”, “ Paratypus Sandracottus jaechi n. sp. Wewalka & Vazirani 82 ” [red label] ( NHMUK) . Examined.

Redescription.

Body oval, somewhat broadened posteriorly, completely black and shiny. Ventral side and legs completely black (Figs 9 , 54 ).

Head black. Surface shiny, very superficially shagreened, covered with small and very dense punctures and of larger much sparser ones, the latter more numerous on frons. Clypeal grooves and punctures alongside eyes marked, punctures medium-size and coalescent. Both antennae lacking in holotype.

Pronotum black, sides not margined. Surface very slightly but distinctly shagreened, with very dense punctation; punctures small, less impressed than on head. Anterior puncture line broadly interrupted in middle, punctures large and strongly coalescent. Posterior puncture line with large and coarsely impressed punctures on middle of each side, building distinct wrinkles.

Elytra black, shiny. Epipleura black. Surface distinctly shagreened and covered with double punctation; smaller punctures with very small and dense punctures, larger one with much more sparser ones. Puncture lines with groups of medium-sized punctures mostly grouped by five or six punctures; discal row almost complete and strongly impressed. Sutural puncture line incomplete, marked only by few punctures along suture.

Ventral side black. Legs black. Prosternal process almost flat, short and broad, lanceolate, 1.4 × longer than broad, flattened and finely but distinctly sculptured; posterior margin broadly rounded. Metatibial spurs bifid. Metatibia with sparse medium-sized punctures on whole surface. Setae along posterior margin of middle femora sparse and ~ 2 / 3 of the width of mesofemora at the base. Ventrites II – VI very superficially shagreened, distinctly longitudinally wrinkled on whole lateral parts, densely covered with very small punctures and with very large sparser ones. Posterior margins rounded, deeply bordered with a row of large and coalescent punctures on the middle of each side along the margin. Outer margin of metaventral wings curved. Metacoxal lines short, not reaching apices of metacoxal processes.

Measurements: TL = 14.4–15.0 mm, TL-h = 13.5–13.6 mm, TW = 8.35–8.8 mm.

♂. Protarsomeres I – III strongly enlarged with three larger suckers and ten numerous smaller ones. Mesotarsomeres I – III with two rows of small suckers. Median lobe of aedeagus, in ventral view, broad, flattened parallel-sided on whole length, lobes broadly rounded at apex (Fig. 20 a ). Parameres slightly longer than median lobe, broad and pointed at apex (Fig. 20 b ).

♀. Similar to male. Microsculpture on ventrite VI as in male.

Differential diagnosis.

This species can be easily separated from all other species by its completely black dorsal surface and the shape of the median lobe.

Distribution.

Sri Lanka, only known from the type locality (Fig. 29 ).

Habitat.

The only three specimens were collected at Nuwara Eliya, a hill resort in the mountains of central Sri Lanka. From German and British botanists of the last century the area was well-known for tropical peatland habitats with many unique and endemic plants (e. g., Keilhack 1915 a). Impressive black and white photographs of such peatland pools in central Sri Lanka can be seen in Keilhack (1915 b). Today the area is mostly cultivated and drained. The completely black dorsal surface and venter of S. jaechi may be an adaptation for woodland or peatland ponds and puddles with dark bottoms, decaying leaves, or sedges but no vegetation.

Conservation.

This is a highly endangered if not extinct species. It is by far the rarest species of the genus with a very limited distribution. It is recommended to be listed in the next IUCN red list.

Figures

Figure 29. Distribution of Sandracottus festivus [black dots] and S. jaechi [red square] in the Indian subcontinent.

Figures 8–11. Habitus of 8 Sandracottus insignis (Luzon, Philippines) 9 S. jaechi (paratype from Nuwara Eliya, Sri Lanka) 10 S. maculatus (Thailand) 11 S. rotundus (Sulawesi, Togian Islands).

Figures 20–22. Median lobe of aedeagus in ventral view (a), and right paramere in lateral view (b): 20 Sandracottus jaechi 21 S. maculatus and 22 S. rotundus.

Figures 54–57. Habitus of 54 Sandracottus jaechi (holotype, Sri Lanka, Nuwara Eliya) 55 Sandracottus insignis (Philippines; Luzon, Los Banos) 56 S. maculatus (Borneo, Sabah, Sungai Kinabatangan) 57 S. rotundus (Indonesia, Sulawesi, Togian Islands, Kaldidiri Island).