Sandracottus maculatus ( 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 maculatus ( Wehncke, 1876)

Figs 10 , 21 , 24 , 39 , 41 , 43 , 44 , 56

Hydaticus maculatus Wehncke, 1876: 196 (type locality “ Siam ” [ Thailand]).

Sandracottus wehnckei J. Balfour-Browne, 1944: 355, replacement name for Hydaticus maculatus Wehncke, 1876 (objective synonym of Hydaticus maculatus); Vazirani 1969: 277 (descr., syst.); 1977: 86 (cat.); Nilsson 2001: 84 (cat.).

Sandracottus maculatus ( Wehncke, 1876): Sharp 1882: 686 (comb. nov.); Régimbart 1899: 338 (descr.); Zimmermann 1920: 235 (cat.); Ghosh and Nilsson 2012: 18 (cat.); Balke et al. 2017: 146 (faun., habitat); Atthakor et al. 2018: 93 (faunistics, habitat); Hájek and Nilsson 2024: 91 (cat.).

Sandracottus angulifer Heller, 1934 a: 280 (type locality Davao, Mindanao, Philippines); Hájek and Nilsson 2024: 91 (cat.) (syn. nov.).

Sandracottus palawanensis Satô, 1978: 41 (type locality Sabang, Palawan, Philippines); Hájek and Nilsson 2024: 91 (cat.) (syn. nov.).

Sandracottus nauticus Sharp, 1882: 690 (type locality Borneo); Régimbart 1899: 339; Zimmermann 1920: 235 (cat.); Hájek and Nilsson 2024: 91 (cat.) (syn. nov.).

Type material of Sandracottus maculatus .

Neotype (herein designated): Male, “ Schoenich ” [?], “ Cambodscha ” [yellowish handwritten label], “ Ex. Coll. E. WEHNCKE Acq 1884 ” [white printed label], “ NEOTYPUS Hydaticus maculatus L. Hendrich & M. Brancucci des. 2010 ” [red printed label] ( MNHN) . Examined.

Comments on classification.

It was impossible to find any type material labelled “ Siam ” among the historical specimens in the NHMUK, MNHN, and ZHMB, so we decided to designate a neotype from Cambodia found in Wehncke´s collection and deposited in MNHN. The neotype is designated to support taxonomic stability, as there are several morphological similar Sandracottus species described from the Indomalayan region, and it is paramount for present and future investigations to possess unambiguously characterised name-bearing specimens for all Indomalayan species of the genus.

Type material of Sandracottus angulifer .

Holotype: Male, “ Davao Mindanao Baker ”, “ 7251 ”, “ S. angulifer Typus ” [red label], “ 1932 12 ”, “ Staatl. Museum für Tierkunde, Dresden ”, “ Sandracottus maculatus ( Wehncke, 1876) Hendrich & Brancucci det. 2006 ” ( SMTD) . Examined.

Type material of Sandracottus palawanensis .

Holotype: Male, “ Sabang , Palawan Philippines July 13, 1977 M. Sâto leg. ” [handwritten], “ HOLOTYPE Sandracottus palawanensis M. Satô DET. M. SATÔ 1978 ” [red label], “ Sandracottus maculatus ( Wehncke, 1876) Hendrich & Brancucci det. 2010 ” ( NMST) . Examined.

Type material of Sandracottus nauticus .

Holotype: Male, “ Borneo 987 nauticus ”, “ Type H. T. ”, “ Sharp Coll. 1905-313 ” ( NHMUK). “ Sandracottus maculatus ( Wehncke, 1876) Hendrich & Brancucci det. 2006 ”. Examined.

Additional material.

(150 specimens): • Cambodia: 1 ex., “ Cambodia Pailin 200 m 11. - 16. VI. 2008 S. Murzin leg. Coll. Hendrich " ( CLH). • Laos: 7 exs., “ LAOS centr., Kham Mouan Prov. Nakai vill. env. ca 70 km NNE Muang Khammouan, 500–600 m 17 ° 43 ' N, 105 ° 09 ' E, 7. - 25. V. 2002 M. Strba leg. / Coll. HENDRICH ” ( CLH); 1 ex., “ LAOS south, Attapeu prov. Bolaven Plateau 18. - 30. IV. 1999, 15 km SE of Ban Houaykong, NONG LOM (lake) env., N 15 ° 02´E 106 ° 35´, alt. 800 m, E. Jendek & O. Sausa leg. ” ( CLH); 1 ex., “ Champasak Prov., Ban Nam Touad env. (near Xe Katamtok), village, agricultural lands, old secundary and degraded primary forest, light trapping, 500–800 m, 15 ° 06 ' N, 106 ° 35 ' E, 8. - 10. VI. 2010, leg. M. Geiser & D. Hauck ” ( NHB); 1 ex., “ Northern Vientiane Prov. Vang-Vieng, 300 m, N 18 ° 55.23 E 102 ° 26.55, 10. - 15. V. & 1. - 6. VI. 2001, J. Kolibac leg. ” ( NMB); 1 ex., “ Umg. Vientiane, III. - IV. 1963, coll. M. Brancucci ” ( NMB); 2 exs., “ Khammouan Prov., Ban Khoun Ngeun, 200 m, 18 ° 07 ' N 104 ° 29 ' E, 24. - 29. IV. 2001, V. Kuban leg. ” ( NMB); 8 exs., “ Khammouan Prov., Nakai env., 500–600 m, 22. V. - 8. VI. 2001, 17 ° 43 ' N 105 ° 09 ' E, E. Jendek & O. Sausa leg. ” ( CHH, NMPC); 1 ex., “ CHAMPASAK prov., Bolavens Plateau, waterfall ca., 2 km E TAD KATAMTOK, 15 ° 08.1 ' N, 106 ° 38.8 ' E, 415 m, 10–12. V. 2010, J. Hájek leg. ” ( NMPC). • Thailand: 1 ex., “ N-Thailand, Khon Kaen Prov., Si Chom Phu, 220 m, 16 ° 8531 N, 102 ° 2526 E R. Ohnesorge, IX. 2012 ”, “ coll. A. Skale Hof / Germany ” ( CAS); 1 ex., “ Thailand 25 V 52 REElbel ”, “ Kanchanaburi ” ( USNM), 14 exs., “ Nakhon Ratchasima Province, Sakaerat Biosphere Reserve, King Cobra Cave, Thailand Coords: 14 ° 30.536 ’ N, 101 ° 55.921 ’ E, 362 m a. s. l., 27 Oct 2013, W. Atthakor leg., Sakaerat Expedition, led by Professor Somsak Panha of Chulalongkorn University ” ( CSUT); 1 ex., “ N Thailand, Doi Pho Ka N. P. Road from Pua 1 km after Park Hq. m 1400, small pools on rock (24) 2. I. 1999 P. Mazzoldi leg. ” ( CPM); 2 exs., “ Siam: MeSong Forest IV. 1919 E. J. Godfrey 1920-244 ” ( NHMUK); 2 exs., “ E Thailand, Ko Chang White Sands Beach, 10. XII. 1990, M. Jäch leg. (12) ” ( NMW); 1 ex., “ Prov. Rayong, Khao Chamao NP, 12. & 13. XII. 1990, M. Jäch leg. (14) ” ( NMW); 1 ex., “ Tham Sakoen NP, No. 21, 29. - 30. XI. 2003, 19 ° 23 ' N 100 ° 38 ' E, Peregovits, Foldvari, Korosi, Szappanos & Maklari-Kis leg. ” ( TDMB); 2 exs., “ Pak Lag, 14. VIII. 1918, Jeanvoine ” ( MNHN); 17 exs., “ Pak Lag 13. VIII. 1918 V. de Salvaza ” ( MNHN); 6 exs., “ Pak Lag, 13. VIII. 1918 V. De S. ”, “ Samml. A. Zimmermann ” ( ZSM); 3 exs., “ Pak Lag 18. VII. 1918 no. 2119 V. de S. ” ( MNHN, ZSM). 2 exs., “ Thailand, E Bangkok, Nakhon Nayok: Khlong Maduea, 14 ° 21 ' 17 " N, 101 ° 16 ' 22 " E, 16. 03. 2017, leg. H. Shaverdo ” ( NMW); 3 exs., “ Thailand, Phetchabun Province, near Nam Nao National Park, Route 2216 then small road off, in village Khlong Choen, 16 ° 40 ' 29 " N, 101 ° 44 ' 01 " E 21. 03. 2017, leg. H. Shaverdo ” ( NMW). • Vietnam: 1 ex., “ VietnamN, Quang Binh prov. 1 km N of Cha Lo, 400 m Vietnam-Laos border area 17 ° 41 ' 22 ´´ N 105 ° 45 ' 45 ´´ E, L. Dembicky leg., 11. - 24. iv. 2010 ” ( NMB); 1 ex., “ Tonkin Env. De Hoa Binh J. Laisi 1902 “, “ S. maculatus Wke ”, “ Dr. Régimbart vidit 1905 ” ( MNHN); 1 ex., “ Museum Paris Cochinchine ” ( MNHN); 3 exs., “ Hoa Binh Tonkin ” ( MNHN); 3 exs., “ Lactho Tonkin A. de Cooman ” ( MNHN); 1 ex., “ S Vietnam, Saigon, jardin botanique [botanical garden], octobre 1870, A. Krempf leg. ” ( MNHN); 1 ex., “ Hoa Binh (Tonkin) A. de Cooman ” ( MNHN); 3 exs., " Hoa Binh (Tonkin) A. de Cooman ” ( MNHN); 2 exs., “ Tonkin occ. env. de Hoa Binh 1919 A. de Cooman ” ( MNHN); 4 exs., “ S-Vietnam, Nam Cat Tien NP, 1. - 15. V. 1994, Pacholatko & Dembicky leg. ” ( NMW); 1 ex., “ Vietnam, Dong NAI, Nam Cat Tien NP, 120 m, 18 - IX- 1998, leg. L. J. Wang ” ( CLJW). • Malaysia: " E-Malaysia, Sabah Borneo, Mt. Trus [= Trusmadi or Trus Madi] March-April 2010 Local leg. ”, “ coll. A. Skale Hof / Germany ” ( CAS); 1 ex., “ NE Borneo Sandakan, Coll. Guignot ” ( MNHN); 1 ex., “ Hydaticus sp. ? Pinang " [West Malaysia, Penang], “ maculatus Wehncke ” [handwritten label by Régimbart] ( MNHN); 1 ex., “ Borneo Sandakan Windrath ”, “ nauticus Shp ” ( MNHN), 1 ex., “ Borneo, Kinabalu [Sabah], Whitehead, Fry Coll. 1905-100 ” ( NHMUK); 1 ex., “ Borneo 987, Sharp Coll. 1905-313 ” ( NHMUK); 3 exs., “ Borneo, Sabah, Kampung Pisang, Pisang env., tributary of Kuamut river, 29. VI. 1998, J. Kodada & F. Ciampor leg. ” ( NMW); 1 ex., “ Borneo Sabah, Hot Springs, 26. V. 1999, Bacovský leg. ” ( NMPC); 20 exs., “ Borneo, Sabah, Sungai Kinabatangan, stream near Danau Blandung Besar, 11. IV. 1994, H. K. Lua leg. ” ( CLH, ZRC); 2 exs., “ Sabah, Kinabatangan riv. 8. - 15. VI. 2003, Uncle Tan´s camp, J. Šťastný leg. ” ( CJS); 1 ex., “ Dindings 96-85 ” [Malaysia, Perak, Manjung District], “ Determined by Dr Régimbart Sandracottus maculatus v. nauticus Sharp ”; 1 ex., “ Ex. Coll. E. Wehncke Acq 1864 ” ( MNHN); 3 exs., “ West Malaysia, Penang 988, Sharp Coll. 1905-313 ” ( NHMUK); 5 exs., “ West Malaysia, Penang, Pascoe Coll. 93-60 ” ( NHMUK). • Indonesia: 1 ex., “ Ned. Indie Leg. A. Koller ”, “ Coll. F. C. Drescher ” ( RMNH); 5 exs., “ Sumatra Palembang M. Knappert ” ( RMNH); 7 exs., “ East Kalimantan, Distr. Damai 12. VII. 1995 Ngelung Stream Mazzoldi P. leg. ” ( CPM); 1 ex., “ East Kalimantan 12. VII. 1995, Distr. Tingai stream near Sembuan, opening in forest – leg. P Mazzoldi ” ( CPM); 1 ex., “ Java Occ. Toeroe 1902 ”, “ Museum Paris ex. Coll. Oberthür 1952 ” ( MNHN); 1 ex., “ Java ex. J. Waterstradt 1904 ” ( NMHN); 1 ex., “ Java ”, “ maculatus Wehncke (MNHN); 1 ex., “ Malang Java ” ( MNHN); 1 ex., " Java, Prov. Pasuruan Kalipari, 300–500 m, 1891, W. Doherty leg. " ( MNHN); 1 ex., " Java, Blume leg. " ( RMNH); 1 ex., " Java, Muller leg. " ( RMNH); 4 exs., “ Z. - Sumatra, Ranau, 500–700 m, Juli 35 ” ( RMNH); 1 ex., “ SW Java, Gautang Bay, III. 1937, M. A. Lieftinck leg. ” ( MNHN); 3 exs., “ Sumatra, Palembang ” ( MNHN); 1 ex., “ Sumatra, Dolok Merangir, 8. V. - 10. VI. 1983, E. W. Diehl leg. ” ( NMB); 1 ex., “ Mentawai Islands, Siberut, 5–50 m, 3. IV. 2005, S. Jákl leg. ” ( NMPC); 2 exs., “ Sumatra, Palembang Coll. Peschet ” ( MNHN); 2 exs., “ Sumatra Palembang ”, “ Samml. A. Zimmermann ” ( ZSM); 1 ex., “ Sumatra Medan Hayek leg. ( ZSM). • Philippines: 1 ex., “ Mindanao Davao XII. 1932, Baker leg. ” ( SMTD); 1 ex., “ Mindanao ” ( MNHN); 1 ex., “ Philippines: Luzon, Bicol, Camarines Sur, Lagonoy ca. 13 ° 44 ' 15.7 " N, 123 ° 31 ' 16.1 " E 09.2019 leg. local collector ” ( CLW).

Remarks.

Specimens from Borneo and Sumatra with reduced yellow basal markings on elytra (habitus near femoralis ) were described as S. nauticus Sharp. In the shape of the median lobe of aedeagus, some specimens from Borneo lies between S. femoralis and S. maculatus from mainland Asia. Furthermore, we do not have any molecular data for either form, so we here list S. nauticus as an objective junior synonym of S. maculatus .

Redescription.

Body large, broad oval, submatt, only slightly shiny, black with ferrugineus brown markings. Ventral side completely dark brown to black, legs testaceous, hind legs somewhat darker.

Head testaceous with posterior part broadly black leaving free two small testaceous spots on vertex (Figs 10 , 56 ). Surface submatt, shagreened, consisting of dense and minute punctures but not very uniform in size and of larger and much sparser ones, more numerous on frons. Clypeal grooves and punctures alongside eyes marked, punctures medium-sized but coalescent. Antennae testaceous; antennomeres slender, antennomere V 4 × as long as broad.

Pronotum black with margins broadly testaceous, submatt (Figs 10 , 56 ). Surface distinctly shagreened, with very dense punctation; punctures medium-sized and distant of only 1–2 × their own diameter. Anterior puncture line interrupted in middle; punctures relatively small but coalescent, building wrinkles and becoming sparse towards middle and lacking in very middle of anterior margin. Posterior puncture line with coarse and coalescent punctures in middle of each sides building distinct wrinkles, distinctly smaller and spaced on disc.

Elytra black with testaceous markings consisting of one basal band sometimes reduced to different spots at base, one postmedian band, one preapical short and reduced band, and an apical spot (Figs 10 , 56 ), submatt. Epipleura ferrugineus brown. Surface distinctly shagreened and covered with small and dense punctures as well as with larger and much more sparser ones. Puncture lines with groups of medium-sized punctures mostly grouped by five or six punctures; groups closer together on discal row. Sutural puncture line marked only by few punctures on apical part.

Ventral side dark brown. Legs particularly fore and mid legs testaceous, hind legs ferrugineus brown to dark brown. Prosternal process short and broad, 1.4 × longer than broad, flattened finely but distinctly sculptured; posterior margin broadly rounded. Metatibia with sparse medium-sized punctures on whole surface. Ventrites II – VI very superficially shagreened, slightly and longitudinally wrinkled on lateral parts, densely covered with very small punctures and larger sparser ones. Posterior margins rounded, deeply bordered with some large coalescent punctures on middle of each side along margin.

Measurements: TL = 13.4–16.6 mm, TL-h = 13.1–15.2 mm, TW = 8.5–10 mm.

♂. Protarsomeres I – III strongly enlarged with three larger suckers and numerous smaller one. Mesotarsomeres I – III with two rows of small suckers. Median lobe of aedeagus, in ventral view, elongate, parallel-sided on complete length, lobes narrowly rounded at apex (Fig. 21 a ). Parameres narrow and elongate, and slightly longer than median lobe (Fig. 21 b ).

♀. Similar to male. Pro- and mesotarsi not enlarged. Microsculpture on ventrite VI as in male.

Differential diagnosis.

The species is clearly distinguished from all other Indomalayan species of the genus by its colouration and larger size. It is the largest species of the genus. From the dorsal colouration S. maculatus is near to S. femoralis which is generally smaller in size (see S. femoralis ). Furthermore, both species can be separated by the shapes of their median lobes.

Distribution.

Cambodia, Laos, Thailand, Vietnam, Malaysia (Sabah), Indonesia (Kalimantan, Sumatra, Java, Siberut) and Philippines (Luzon, Mindanao, Palawan) (Fig. 24 ). Specimens were collected from approximately sea level to 800 m a. s. l.

Habitat.

A widespread but rare species. According to various collectors all recent records are from well vegetated pools, forest pools, or rest pools of intermittent streams and rivers, mainly located in primary rainforest (Fig. 43 ). At least most habitats are partly shaded and enriched with decaying leaves and twigs (Fig. 44 ). In Thailand (Sakaerat Biosphere Reserve) the species was collected at the end of the dry season in a rest pond of a rocky stream, with very dark water and accumulated leaf litter. The pond was more or less permanent but with a high fluctuation of water level (Fig. 41 ). The species was syntopic with S. hunteri ( Atthakor et al. 2018) . In Vietnam, the species was collected in shallow water made by a passing jeep on a path. Syntopically occurring dytiscid species include Leiodytes kualalipis Balke, Wang, Bergsten & Hendrich, 2017 , L. nicobaricus (Redtenbacher, 1867) , and Hydroglyphus orientalis (Clark, 1863) ( Balke et al. 2017) . In Laos, S. maculatus was collected in a residual pool near the river (Fig. 39 ). The pool had a diameter of nearly 1 m, depth was ~ 40 cm, bottom with a thick layer of decaying leaves (Hájek pers. comm. 2023).

Figures

Figure 24. Distribution of Sandracottus bizonatus [red squares] and S. maculatus [black dots] in Southeast Asia.

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 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 43–45. Habitats of Sandracottus 43, 44 Malaysia, Sabah, Kinabatangan riv. 8. - 15. VI. 2003, Uncle Tan´s camp, habitat of S. maculatus (photos: J. Šťastný) 45 Indonesia, Sulawesi, Togian Islands, Kaldidiri Island near Paradise Island Resort, Babirusa puddles (on the left), habitat of S. rotundus (photo: J. Haft).

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).