Sandracottus chevrolati ( Aubé, 1838 )

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 chevrolati ( Aubé, 1838)

Figs 3 , 14 , 25 , 49

Hydaticus chevrolati Aubé, 1838: 164 (type locality Timor, Indonesia).

Sandracottus chevrolati ( Aubé, 1838): Régimbart 1899: 334 (descr.); Zimmermann 1920: 234 (cat.); Hájek and Nilsson 2024: 91 (cat.).

Hydaticus mixtus Blanchard, 1843 : plate 4, fig. 2 (type locality Timor, Indonesia) (syn. nov.).

Comments on classification.

The verbal description of H. mixtus was published by Blanchard (1853). However, before the publication of the text, the colour plates to this book were published separately during the years 1842–1854 (see Clark and Crosnier 2000). Therefore, the plates must be considered as the original description ( ICZN 1999: Article 12.2. 7). Sandracottus mixtus was regarded as a junior subjective synonym of Dytiscus fasciatus Fabricius, 1775 (= primary homonym of Dytiscus fasciatus DeGeer, 1774 ) by Vazirani (1969). However, Vazirani mentioned that he had no possibility to see the type or the original description of that species. Although we did not see the type specimen of H. mixtus , the figure which serves as the original description is very accurate and refers without any doubt to the species described by Aubé (1838) under the name H. chevrolati . In addition, the type locality of both species is the same (Timor), and we are not aware of any records of Sandracottus fasciatus [ = hunteri ] east of the Wallace’s line. Therefore, we consider Hydaticus mixtus as a junior subjective synonym of H. chevrolati .

Type material of Hydaticus chevrolati .

Lectotype (herewith designated): Male, “ Timor ” [handwritten label], “ typus ” [handwritten label] “ Lectotype Hydaticus chevrolati Aubé des. L. Hendrich & M. Brancucci 2010 ” [red printed label] ( MNHN) . Paralectotype: Female, “ Timor ” [handwritten label], “ Paralectotype Hydaticus chevrolati Aubé des. L. Hendrich & M. Brancucci 2010 ” [red printed label] ( MNHN) . Examined.

Type material of S. mixtus .

Not examined.

Additional material.

(157 specimens): Indonesia: • Lombok: 1 ex., “ Indonesia: N Lombok, Senaru waterfall, alt. m. 0470, 13. x. 1991, Huijbregts, Krikken ” ( RMNH). • Pantar: 2 exs., “ Indonesia, Lesser Sundas, Pantar Isl, east coast, Tanah Labnag env., 350 m, S. Jakl leg. 9. - 21. iii. 2006 ” ( NMPC). • Sumba: 7 exs., “ O. Sumba Prai Jawang Rende Wai 14. 7. 1949 Dr. Bühler Dr. Sutter ” ( NMB); 1 ex., “ W. Sumba Mata Kori Waimangura 23. 8. 1949 Dr. Bühler Dr. Sutter ” ( NMB); 1 ex., “ W. Sumba Baing 30. 6. 1949 Dr. Bühler Dr. Sutter ” ( NMB); 1 ex., “ O. Sumba Mau Maru 18. 7. 1943 Dr. Bühler Dr. Sutter ” ( NMB); 1 ex., “ O. Sumba Kodi 8. 8. 1949 Dr. Bühler Dr. Sutter ” ( NMB); 1 ex., “ O. Sumba Melolo 28. Mai 1949 Dr. Bühler-Dr. Sutter ” ( NMB); 1 ex., “ Indonesia, Lesser Sundas Sumba East, 10–20.6. 2006, Luku Melolo N. R., 300–500 m, S. Jakl leg. ” ( CLH); 2 exs., “ Sumba East, Melolo env., Luku Melcio, 300–600 m, 7. - 9. II. 2001, P. Votruba leg. ” ( CJS); 2 exs., “ Sumba Island mer., Tarimbang env., 0–100 m, 2. II. - 3. II. 2001, S. Jákl leg. ” ( NMPC); 2 exs., “ East Sumba 550 m, Luku Melolo N. R. 1. - 10. 7. 2005 ” ( CLH); 1 ex., “ Sumba Island or., Mt. Wangameti, Kanangar env., 600–800 m, 10. II. 2001, S. Jákl leg. ” ( NMPC); 11 exs., “ Indonesia, East Sumba, 20 km S of Waingapu Wairinding, 300 m, 30. I. - 2. II. 2001, P. Votruba leg. ” ( CLH, NMPC). • Sumbawa: 33 exs., “ Sumbawa, Dompu-Empang, restpools, 90 m, 15. ix. 2011, 08 35.563 S 118 17.454 E (SUMB 06) ” ( MZB, ZSM); 1 ex., “ Sumbawa ” ( MNHN); 2 exs., “ Savu I. [= Savu Island] Viii 96 Hvereti ” ( MNHN); 3 exs, “ Museum Paris Coupang Hombron 1841 ” ( MNHN); 7 exs., “ Sumbawa Colffs. ”, “ Ex. Musaeo Van Landsberge ” ( MNHN); 1 ex., “ Sumbawa ” ( MNHN); 2 exs., “ v. Lansb., Sumbawa ” ( RMNH); 1 ex., “ Sumbawa, 56993, Fry Coll. 1905-100 ” ( NHMUK); 2 exs., “ Sumbawa ” ( MNHN); 1 ex., “ Indonesia, W-Sumbawa, Batoe Doelang, 10. - 15. V. 1927, B. Rensch ” ( CGW). • Flores: 2 exs., “ Indonesia, Flores, Rinca, V. 1990, C. H. S. Watts leg. ” ( CLH, SAMA). • Tanimbar: 6 exs., “ Indonesia, Tanimbar Yamdema isl., Lorulun, 20 km NE of Saumlaki, 150 m, 26.11. - 4. 12. 2006, M Oboril lgt. ” ( CLH, ZSM); 2 exs., “ Indonesia, Tanimbar-Yamdena, Mams, 21 km N of Saumlaki, 27. XI. - 11. XII. 2005, J. Horák leg. ” ( NMPC); 13 exs., “ Indonesia, Tanimbar isls, Lorulun, 20 km NE of Saumlaki, 150 m, 25.11. - 24. 12. 2006, St Jakl lgt. ” ( CLH, ZSM). • Timor: 1 ex., “ Indonesia, West Timor Buraen env. 28 km S Kupang 400 m, 16. - 21. 12. 2005 St. Jakl leg. ” ( CLH); 1 ex., “ TIMOR ISL Buraen env. 60 km SE Kupang 350 m, 10. - 21. 2. 2006 St. Jakl leg. ” ( CLH); 4 exs., “ Timor, Naikliu area, restpools in dry forest, 130 m, 3. x. 2011, 09 58.425 S 123 41.439 E (TIM 11) ” ( MZB, ZSM); 1 ex., “ Timor, alte Sammlung ” ( ZSM); 1 ex., “ Timor ” ( RMNH); 6 exs., “ Macklot, Timor ” ( RMNH); 3 exs., “ Dr. H. ten Kate, Timor centr. ” ( RMNH); 4 exs., “ S. O. Celebes, J. Elbert, 1909 ” ( RMNH); 1 ex., “ W. P. de Roever, Nenas en omgeving, Moetisgebergte Timor, Sept. 1937 ” ( RMNH); 6 exs., “ Tim. [Timor] 6756 ” ( NHMUK); 1 ex., “ Tim. [Timor], Wallace, Celebis ( Hydaticus ) MS Clark ” ( NHMUK); 1 ex., “ Timor 978 var., Sharp Coll. 1905-313 ” ( NHMUK); 2 exs., “ Timor, Lelogama, Mai 1911, Haniel ”, “ Samml. A. Zimmermann “ ( ZSM); 1 ex., “ Timor ”, “ Coll. C. Felsche Geschenk 1907 ” ( SMTD). • Sulawesi: 2 exs., “ Manado, Celebes [Sulawesi] 2014 ” ( NHMUK); 1 ex., “ S. O. Celebes T. Elbert 1909 ”, “ Rambi bis Mengkoka ”, “ ex Museum Buitenzorg ”, “ Sandracottus chevrolati Aubé det. A. Zimmermann ” ( DEI); 2 exs., “ Celebes [Sulawesi] Posso [Poso] See Drs. Sarasin ” ( NMB, SMTD); 1 ex., “ SO Sulawesi, I. Albert ”, “ Samml. A. Zimmermann ” ( ZSM). • Moluccas: 1 ex., “ Moluccas ” ( MNHN); 2 exs., “ Moluccas Batchian [most probably mislabeled] J. Waterstradt 1902 ” ( MNHN); 1 ex., “ Rotti Carl Auriv. ”, “ Samml. A. Zimmermann ” ( ZSM); 2 exs., “ Kisser Inseln Mai 1901 ” [Pulau Kisar], “ Samml. A. Zimmermann ” ( ZSM); 2 exs., “ Molukken Ins. Roma ” [Pulau Romang], “ Samml. A. Zimmermann ” ( ZSM). • Timor-Leste: 1 ex., “ Timor-Leste, 6. ii. 2011, Ossu, Mundo Perdido Mts. 945 m, 8 ° 42 ' 47.6 " S, 12 ° 49 ' 29 " E ” ( NMPC).

Redescription.

Body broad oval, shiny, testaceous with black markings. Ventral side completely dark brown to black, legs testaceous, hind legs somewhat darker (Figs 3 , 49 ).

Head testaceous with posterior part and broadly so on posterior half alongside as well as two elongate spots on clypeus black, shiny (Figs 3 , 49 ). Punctation consisting of dense and very numerous punctures of different sizes and of larger, much sparser ones, particularly numerous on frons. Clypeal grooves, punctures alongside eyes and a transverse depression beside eyes distinctly impressed, punctures large and coalescent. Antennae testaceous; antennomeres slender, antennomere V 4.5 × as long as broad.

Pronotum testaceous with a median black marking reaching from posterior to anterior margins; long and broad on posterior, distinctly shorter and narrower on anterior margin and strongly constricted in middle (Figs 3 , 49 ). Surface very superficially shagreened, almost not discernible, with dense punctation; punctures medium-sized mixed with smaller ones. Anterior and lateral puncture lines dense and coalescent, punctures becoming sparse towards middle and lacking in very middle of anterior margin. Posterior puncture line with coarse and coalescent punctures in middle of each side, distinctly smaller and spaced on disc.

Elytra testaceous to ferrugineus brown with black markings consisting of three transverse bands; particularly characterised by the presence of longitudinal testaceous subsutural spots (Figs 3 , 49 ). Epipleura testaceous to ferrugineus brown. Surface very slightly and superficially shagreened and covered with a double punctation, a smaller and dense one as well as a larger one more sparse. Puncture lines with groups of medium-sized punctures mostly grouped in five or six punctures, groups closer together on discal row.

Ventral side dark brown. Legs, particularly fore and mid legs testaceous, hind legs ferrugineus brown to dark brown. Prosternal process short and broad, 1.5 × longer than broad, flattened finely but distinctly sculptured; posterior margin broadly rounded. Whole surface very superficially shagreened and finely punctured. Metatibia with sparse medium-sized punctures on outer half. Ventrites II – VI very superficially shagreened, slightly and longitudinally wrinkled on lateral parts, whole surface densely covered with very small punctures, with sparser larger ones. Posterior margins rounded, bordered with some large and coalescent punctures on the middle of each side.

Measurements: TL = 13.0– 13.5 mm, TL-h = 11.2–12.4 mm, TW = 8.0– 8.5 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, broadened on apical third, then tapered up to apex, here broadly rounded (Fig. 14 a ). Parameres basally broad and pointed at apex (Fig. 14 b ).

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

Differential diagnosis.

The dorsal colour pattern of the Indonesian S. chevrolati is near to the Indian S. festivus but S. chevrolati can be easily separated by its smaller size (TL = 10–13.5 mm, S. festivus : TL = 14.7–15.5 mm) (Figs 3 , 49 ), its distributional range (Figs 25 , 29 ), and shape of median lobe and parameres (Figs 14 a, b , 16 a, b ).

Distribution.

Indonesia: Lesser Sunda Islands east of the Wallace Line (Lombok, Sumba, Sumbawa, Flores), Tanimbar, Timor, south-eastern Sulawesi, and southern Moluccas (Pulau Romang) (Fig. 25 ). Old records from northern Sulawesi and Bacan Island need to be confirmed. Specimens were collected between 90 and 800 m a. s. l.

Habitat.

The specimens from Rinca ( Flores) and Sumbawa were collected in rest pools of an almost dry stream bed, partly shaded by monsoonal rainforest. The bottom consisted of rocks and coarse sand, covered with rotten leaves (C. H. S. Watts and M. Balke pers. comm. 2010).

Figures

Figure 25. Distribution of Sandracottus chevrolati in Indonesia.

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

Figures 1–3. Habitus of 1 Sandracottus bakewellii bakewellii (Northern Territory, Australia) 2 S. bizonatus (Borneo, Sabah, Kinabalu) 3 S. chevrolati (Sumba Island, Indonesia).

Figures 12–15. Median lobe of aedeagus in ventral view (a), and right paramere in lateral view (b) 12 Sandracottus bakewellii bakewellii 13 S. bizonatus 14 S. chevrolati and 15 S. dejeanii.

Figures 46–49. Colouration and habitus of 46 Sandracottus bakewellii bakewellii (Australia, Northern Queensland, Atherton Tableland, Mareeba) 47 S. bakewellii guttatus (Australia, Northern Territory, Ormiston Gorge) 48 S. bizonatus (Borneo, Sabah, Keningau) 49 S. chevrolati (Indonesia, Sumba Island, Waingapu).

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.