Sandracottus insignis ( Wehncke, 1876 )

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 insignis ( Wehncke, 1876)

Figs 8 , 19 , 28 , 42 , 55

Hydaticus insignis Wehncke, 1876: 194 (type locality Philippines, “ Insel Luzon ”); Sharp 1882: 687 (descr.).

Sandracottus insignis ( Wehncke, 1876); Régimbart 1899: 338 (tax., descr.); Freitag et al. 2016: 8 (check list); Hájek and Nilsson 2024: 91 (cat.).

Hydaticus baeri Régimbart, 1877: 99 (type locality Philippines, “ Manille ”); Zimmermann 1920: 234 (syn., cat.).

Sandracottus ornatus Sharp, 1882: 689 (type locality Borneo); Vazirani 1977: 84 (stat. nov.).

Sandracottus insignis ssp. ornatus Sharp, 1882; Vazirani 1977: 84 (cat.); Hájek and Nilsson 2024: 91 (cat.) (syn. nov.).

Type material of Sandracottus insignis .

Lectotype (herewith designated): Female: “ Semper ” [white handwritten label with black fram]; “ Luzon ” [handwritten yellowish label], Ex. Coll. E. WEHNCKE Acq. 1884 ” [printed white label], “ Lectotype Hydaticus insignis Wehncke Hendrich & Brancucci des. 2010 ” [red printed label] ( MNHN). Examined.

Type material of Sandracottus baeri .

Lectotype (herewith designated): Male: “ Manille Baer ”, “ Typus ”, “ Type ”, “ Sandracottus baeri Rég. ”, “ Lectotypus Hydaticus baeri Brancucci & Hendrich 07 ” [red printed label], “ Sandracottus insignis (Wehncke) det. M. Brancucci & L. Hendrich 07 ” [white printed label] ( MNHN) . Paralectotypes: 2 males, “ Manille Baer ”, “ Typus ”, “ Type ”, “ Sandracottus baeri Rég. ”, “ Paralectotypus Hydaticus baeri Brancucci & Hendrich 07 ” [red printed label], “ Sandracottus insignis (Wehncke) det. M. Brancucci & L. Hendrich 07 ” [white printed label] ( MNHN) . Examined.

Type material of Sandracottus ornatus .

Holotype: Female: “ Borneo 986 ornatus ”, “ Type H. T. ”, “ Sharp coll. 1905-313 ”, “ Sandracottus insignis (Wehncke) Hendrich det. 2008 ” ( NHMUK) . Paratype: Female: “ Borneo 986 1905-313 ”, “ Sandracottus insignis (Wehncke) Hendrich det. 2008 ” ( NHMUK) . Examined.

Remarks.

The type locality of S. ornatus , “ Borneo ”, needs to be confirmed. Sandracottus insignis / ornatus has never been reported from Borneo again. However, it cannot be ruled out that the species occurs there, as some dytiscids that occur in the south of the Philippines have also been reported from the north of Borneo. From what is known so far, S. insignis appears to be endemic to the Philippines.

Additional material.

(10 specimens): • Philippines: 1 ex., “ Balabac ” [handwritten label], “ ornatus Shrp ” [handwritten label] ( MNHN); 1 ex., “ Montalban ” [Luzon], “ Nr. 6 Fld. - H. ” [printed label], “ baeri Régb. Insignis Sharp ” [handwritten label by Régimbart] ( MNHN), 2 exs., “ Mindanao ” ( MNHN); 2 exs., “ Luzon, Los Banos, Mt. Makiling [above the Botanical Garden, 180 m] (3), 13. XI. 1992, H. Schillhammer leg. ” ( NMW); 1 ex., “ Luzon , Pampanga Province, Bano San Juan, Mt. Arayat NP, spring creek, bolders, root packs, riffle, 37 m, 15 ° 10 ' 21.62 " N, 120 ° 45 ' 47.78 " E, 31. X. 2009, H. Freitag leg. ” ( ZSM); 1 ex., “ Polillo [Polillo Islands, Luzon], Taylor ” ( ZSM); 1 ex., “ Palawan, Taytay [10 ° 50 ' N 119 ° 30 ' E], W. Schultze leg. ” ( SMTD).

Redescription.

Body broadly oval, shiny, testaceous with black markings. Ventral side completely dark brown to black, fore and mid legs testaceous, hind legs ferrugineus brown.

Head testaceous with posterior part dark brown as well as two dark brown, oblique, elongated patches on frons (Figs 8 , 55 ). Surface finely microreticulate, particularly on anterior half, just shagreened on rest of surface. Punctation consisting of dense and very small punctures and of larger, much sparser ones, the latter particularly numerous on frons. Clypeal grooves, punctures alongside eyes and transverse depression beside eyes distinctly impressed, punctures large and coalescent. Antennae testaceous; antennomeres slender, antennomere V 4 × as long as broad.

Pronotum testaceous with long and broad dark brown band posteriorly and narrow dark brown band anteriorly (Figs 8 , 55 ). Surface sculpture shagreened with dense punctation; punctures medium-sized. Anterior rows of punctures with dense, strong, and coalescent punctures, shortly interrupted in middle. Lateral puncture lines broad; punctures medium-sized and coalescent. Posterior row limited to few punctures at latero-basal quarter.

Elytra testaceous with black markings leaving four angulous basal testaceous spots, two large postmedian as well as a preapical and an apical testaceous patch (Figs 8 , 55 ). Epipleura testaceous. Surface microreticulate, meshes very small but strongly impressed. Punctation consisting of numerous minute punctures mostly in intersection of meshes and of large sparse punctures regularly spread on whole surface. Puncture lines with groups of medium-sized punctures, discal row almost complete. Sutural puncture line with few small punctures along suture.

Ventral side dark brown. Legs particularly fore and mid legs testaceous, hind legs ferrugineus brown to dark brown. Prosternal process very short and broad, only 1.4 × longer than broad, flattened and superficially sculptured; posterior border broadly rounded. Metacoxa very superficially shagreened and finely punctured; punctures small and sparse; Metatibia with numerous medium-sized punctures on whole outer half, somewhat larger proximally. Ventrites II – VI shagreened, densely covered with very small punctures and larger sparser ones. Posterior margins rounded, bordered with short row of coalescent punctures each side of middle.

Measurements: TL = 12.5–13.1 mm, TL-h = 11.4–12.2 mm, TW = 7.8–8.1 mm.

♂. Protarsomeres I – III strongly enlarged with three larger suckers and numerous smaller ones. Mesotarsomeres I – III with two rows of small suckers. Median lobe of aedeagus, in ventral view, broad, apical half more or less parallel-sided, each part narrowly rounded apically (Fig. 19 a ). Parameres also narrow, slightly longer than median lobe, and gently tapered on apical half (Fig. 19 b ).

♀. Similar to male. Tarsi not enlarged. Microsculpture on ventrite VI as in male.

Differential diagnosis.

The species is clearly distinguished from most other Oriental species of the genus by its characteristic colouration. From the dorsal colouration S. insignis is near to the Indian S. festivus which is generally larger and more elongated. Furthermore, both species can be separated by the shapes of their median lobes.

Distribution.

Philippines: Palawan, Mindanao, Luzon. The record from Borneo seems to be doubtful (Fig. 28 ). Specimens were collected between 40 and 200 m above sea level.

Habitat.

The three specimens at Mt. Makiling were collected in an exposed roadside ditch surrounded by mature second growth lowland rainforest (H. Schillhammer pers. comm. 2005). The single specimen from Bano San Juan at Mt. Arayat NP was collected among root packs in a shallow bay of a slow flowing creek, partly shaded by second growth vegetation (Freitag pers. comm. 2012) (Fig. 42 ). The larvae are still unknown.

Conservation.

A rare species, probably associated with the declining primary lowland rainforests in the Philippines (see Indomalayan species S. bizonatus , S. femoralis , S. maculatus , and S. rotundus ). According to the present knowledge it is an endangered species ( Freitag et al. 2016). It is recommended to be listed in the next IUCN red list.

Figures

Figure 28. Distribution of Sandracottus insignis in the Philippines.

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 16–19. Median lobe of aedeagus in ventral view (a), and right paramere in lateral view (b): 16 Sandracottus festivus 17 S. femoralis 18 S. hunteri and 19 S. insignis.

Figures 37–42. Habitats of Sandracottus 37, 38 Laos, Attapeu prov., Annam Highlands Mts., Dong Amphan NBCA, Nong Fa [puddles near lake shore] and lake, habitat of S. hunteri 39 Laos, Katamtok, rest pools along a rocky river bed, habitat of S. maculatus (photos: J. Hájek) 40 Thailand, near Salawin NP, open and muddy puddle made by elephants (photo: J. Šťastný), and 41 Sakaerat Biosphere Reserve, rocky pool in an otherwise dry stream bed, habitats of S. hunteri and S. maculatus (photo: W. Atthakor) 42 Philippines, Luzon, Pampanga Prov., Bano San Juan, Mt. Arayat NP, spring creek, habitat of S. insignis (photo: H. Freitag).

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).