Gynacantha maclachlani Krüger, 1899

Gynacantha maclachlani Krüger, 1899 View in CoL Figs 22, 23 View FIGURES 22–23 , 25, 26 View FIGURES 24–26

Selected references:

Gynacantha maclachlani View in CoL ;— Lieftinck 1954: 101 (first records from Sumatra: Belitung and “ Sumatra (east)”).

Specimens collected. M1b: 1 ♂ ( RER20 _ AES4 About AES , RER), 22 i 2020; M2f : 1 ♂ ( RER23 _ AES2 About AES ; RER) , at lights at 6:30–7 PM, 17 ii 2023; M5a : 1 ♂ ( RER23 _ AES1 About AES ; RER), 9 ii 2023; M10a : 1 ♂ ( RER23 _ AES13 About AES ; UMRI), 8 vi 2023; P1d : 1 ♂ ( RER23 _ AES12 About AES ; BRIN), 2 vi 2023 .

Remarks. Gynacantha maclachlani is recorded from Riau Province for the first time. See the taxonomic remarks under G. dohrni .

Gynacantha sp.

Specimens collected. M2f: 1 ♀ ( RER23 _ AES4 About AES ; RER) , at lights at ca. 6:45 PM, 14 ii 2023 ; 1 ♀ ( RER23 _ AES5 About AES ; RER) , at lights after 7 PM, 14 ii 2023 ; 1 ♀ ( RER23 _ AES6 About AES ; RER) , at lights after 7 PM, 18 ii 2023, leg. Eco Camp canteen staff; M5a : 1 ♀ ( RER23 _ AES27 About AES ; RER), 28 ix 2023 .

Remarks. None of these females are G. dohrni , most or all of them are probably G. maclachlani but since there could be additional Gynacantha species present in the area, with females difficult to distinguish from those of G. maclachlani , their identity is best left open for now. Note that these undetermined specimens are not included in the count of species recorded from the Kampar Peninsula.

Heliaeschna Selys, 1882

Heliaeschna crassa Krüger, 1899 View in CoL

Selected references:

Heliaeschna crassa Krüger, 1899 View in CoL ;— Fraser 1926: 476 (first record from Sumatra, given as Java with doubts: no more detailed location specified);— Lieftinck 1935a: 22 (first records with definite location from mainland Sumatra: Jambi, Lampung, North and South Sumatra);— Lieftinck 1954: 103 (location given by Fraser 1926 corrected to Sumatra).

Specimens collected. M2f: 1 ♂ ( RER23 _ AES9 About AES ; RER), at lights at 6:30–7 PM, 12 ii 2023 ; 1 ♂ ( RER23 _ AES14 About AES ; BRIN), at lights at ca. 7:15 PM, 4 vi 2023 ; 1 ♂ ( RER23 _ AES15 About AES ), at lights at ca. 6:45 PM, 7 vi 2023 .

Taxonomic remark. The identification of specimens as either H. crassa or H. idae (Brauer, 1865) here is consistent with other such determinations made by the first author. The reader is referred to note 52 in Dow (2021) for a brief discussion of the issues involved; a thorough study of the types and much other material as well as accurate and consistent translations of original descriptions into English is needed and such a study might result in changes to published identifications and even the introduction of an additional name.

Other remark. Recorded from Riau Province for the first time.

Heliaeschna idae (Brauer, 1865)

Selected references:

Heliaeschna idae (Brauer, 1865) View in CoL ;— Lieftinck 1954: 104 (first records from Sumatra: Belitung and “ Sumatra ” without further details).

Specimens collected. M2f: 1 ♂ ( RER23 _ AES17 About AES ; BRIN), in toilet at Eco Camp, 8 vi 2023 , Eco Camp housekeeping staff; 1 ♂ ( RER23 _ AES28 About AES ; UMRI), at lights at 7–7:30 PM, 2 x 2023 ; P1d: 1 ♂ ( RER23 _ AES16 About AES ; RER), 31 v 2023 .

Remarks. There has been no record from mainland Sumatra since the vague “ Sumatra ” in Lieftinck (1954). Recorded from Riau Province for the first time. See the taxonomic remark under H. crassa .

Heliaeschna sp.

Specimens collected. M2f: 1 ♀ ( RER23 _ AES7 About AES ; RER), at lights at ca. 7:30 PM, 9 ii 2023 ; 1 ♀ ( RER23 _ AES8 About AES ; RER), at lights 6:30–7 PM, 9 ii 2023 ; 1 ♀ ( RER23 _ AES18 About AES ; RER), at lights at ca.7 PM, 3 vi 2023 ; 1 ♀ ( RER23 _ AES19 About AES ; RER), at lights at ca.7 PM, 4 vi 2023 ; 1 ♀ ( RER23 _ AES22 About AES ; RER), at lights at ca.6:40 PM, 10 vi 2023 ; 1 ♀ ( RER23 _ AES23 About AES ; RER), at lights at ca. 6:30 PM, 11 vi 2023 ; 1 ♀ ( RER23 _ AES24 About AES ; RER), found in laboratory, 15 vi 2023 ; 1 ♀ ( RER23 _ AES25 About AES ; RER), found in building, 18 vi 2023 , leg Eco Camp housekeeping staff; 1 ♀ ( RER23 _

AES26 About AES ; RER), at lights at ca.6:30 PM, 19 vi 2023, leg Eco Camp canteen staff; M4d: 2 ♀♀ ( RER23 _ AES20–21 About AES ; RER), flying over road at dusk, 9 vi 2023 .

Remarks. In the opinion of the first author, females of H. idae and H. crassa cannot be reliably separated at this time, with the situation complicated by (possible) polymorphism in wing markings. It is therefore better to leave the females identified only to genus. Note that these undetermined specimens are not included in the count of species recorded from the Kampar Peninsula.

Gomphidae

Gomphidia Rambur, 1842 View in CoL

Gomphidia sp.

Remarks. A single male Gomphidia was seen perched at the side of a closed canopy PSF stream (Simpang Sianyir, M 1m) during suboptimal weather conditions on 1 x 2023, but flew away before the boat could be brought into a position from which capture was possible. The individual was very darkly coloured, more so than is typical for any species of Gomphidia known from Sundaland. Two species of Gomphidia have been recorded from Sumatra— G. abbotti Williamson, 1907 and G. machlachlani Selys, 1873 (but see below)—both of these species have been recorded in low pH waters elsewhere (e.g. Dow et al. (2012) for G. abbotti and Dow & Reels (2024) for G. machlachlani ) but G. abbotti can be ruled out by the coloration of the Simpang Sianyir male. Gomphidia machlachlani is darker than G. abbotti and although still not typically as dark as the Simpang Sianyir male, the first author has collected one male almost as dark as that individual in Sarawak. Moreover, G. machlachlani has been found in numbers in very similar conditions at Maludam National Park in Sarawak ( Dow & Reels 2024). Although the Simpang Sianyir male might be G. machlachlani, Lieftinck (1954) questioned the identity of Sumatran material supposedly of that species. Specimens will need to be collected before identification to species can be made.

Whichever species of Gomphidia is present in the Kampar Peninsula, the genus has not been recorded in Riau Province until now.

Ictinogomphus Cowley, 1934 View in CoL

Ictinogomphus acutus (Laidlaw, 1914) View in CoL

Selected references:

Ictinus acutus Laidlaw, 1914 ;— Laidlaw 1914b: 51–52, fig. 1 (original description from Sarawak).

Ictinogomphus acutus (Laidlaw, 1914) View in CoL ;— Lieftinck 1954: 77 (first record from Sumatra: Belitung).

Specimens collected. M1a: 2 ♂♂ ( RER20 _ GOM1 , 4 ; RER), 15 i 2020 ; 1 ♂ ( RER20 _ GOM2 ; BRIN), 15 i 2020 ; 1 ♂ ( RER20 _ GOM3 ; UMRI), 15 i 2020 ; 1 ♂ ( RER20 _ GOM5 ; BRIN), 18 i 2020 ; 1 ♂ ( RER20 _ GOM6 ; UMRI), 19 i 2020 ; 1 ♂ ( RER23 _ GOM2 ; UMRI), 12 ii 2023 ; 1 ♂ ( RER23 _ GOM13 ; UMRI), 14 vi 2023 ; 1 ♀ ( RER23 _ GOM26 ; RER), 4 x 2023; M1f : 1 ♂ ( RER23 _ GOM6 ; BRIN), 17 ii 2023 ; 1 ♂ ( RER23 _ GOM27 ; BRIN), 4 x 2023; M1j : 1 ♂ ( RER23 _ GOM25 ; BRIN), 2 x 2023; M1l : 1 ♂ ( RER23 _ GOM3 ; RER), 15 ii 2023 ; 1 ♂ ( RER23 _ GOM4 ; BRIN), 15 ii 2023; M 1m : 1 ♂ ( RER23 _ GOM5 ; UMRI), 16 ii 2023; M5a : 1 ♂ ( RER20 _ GOM7 ; RER), 20 i 2020 ; 1 ♂ ( RER20 _ GOM8 ; BRIN), 20 i 2020 ; 1 ♂ ( RER20 _ GOM9 ; UMRI), 20 i 2020 ; 1 ♂ ( RER20 _ GOM10 ; RER), 25 i 2020 ; 1 ♂ ( RER23 _ GOM1 ; BRIN), 9 ii 2023 ; 1 ♂ ( RER23 _ GOM12 ; BRIN), 6 vi 2023 ; 1 ♂ ( RER23 _ GOM23 ; BRIN), 28 ix 2023 ; 1 ♀ ( RER23 _ GOM24 ; UMRI), 28 ix 2023 .

Remarks. Recorded from the mainland of Sumatra for the first time. Aside from the record from Belitung and a few records from Pahang (e.g. Norma-Rashid et al. 2001, Dow et al. 2012, Choong et al. 2016), most records of I. acutus are from Borneo. When the habitat has been recorded the species is invariably associated with low pH waters; its preferred habitat is low gradient streams in PSF or other forest formations with low pH and it can sometimes be found at drains with flow at the edge of PSF (although it has not been found in this situation in the Kampar Peninsula).

Ictinogomphus decoratus melaenops (Selys in Selys & Hagen, 1858)

Selected references:

Ictinogomphus decoratus (Selys, 1854) View in CoL ;— Gesriantuti et al. 2018: 200 (first record from Riau).

Ictinus decoratus ?;—Selys 1889: 469 (first record for Sumatra: Bangka).

Ictinus melaenops Selys in Selys & Hagen, 1858;— Karsch 1891: 244 (first record from mainland Sumatra: North Sumatra).

Specimens collected. M1l: 1 ♂ ( RER23 _ GOM8 ; BRIN), 15 ii 2023; M3a : 1 ♀ ( RER20 _ GOM12 ; BRIN), 17 i 2020; M3b : 1 ♂ ( RER20 _ GOM11 ; RER), 17 i 2020; M3c : 1 ♀ ( RER23 _ GOM7 ; RER), 10 ii 2023; M7b : 1 ♂ ( RER20 _ GOM13 ; UMRI), 23 i 2020; M11a : 2 ♂♂ ( RER23 _ GOM17–18 ; RER), 11 vi 2023; M12a : 1 ♀ ( RER23 _ GOM20 ; UMRI), 18 vi 2023; M13a : 1 ♂ ( RER23 _ GOM19 ; BRIN), 18 vi 2023; M13b : 1 ♂ ( RER23 _ GOM21 ; RER), 18 vi 2023; P3b : 1 ♂ ( RER23 _ GOM14 ; UMRI), 30 v 2023; P4a : 1 ♂ ( RER23 _ GOM15 ; RER), 31 v 2023 ; 1 ♂ ( RER23 _ GOM16 ; BRIN), 2 vi 2023; P5d : 1 ♂ ( RER23 _ GOM22 ; BRIN), 21 vi 2023; P5e : 1 ♂ ( RER23 _ GOM28 ; UMRI), 22 ix 2023 .

Remarks. Generally common in the Kampar Peninsula. Although no specimens were collected there, this species is abundant on the lower part of Sungai Serkap (M1a). It is also far more abundant along the banks of the Kampar River than the single specimen collected there suggests. On the Kampar River many individuals were also seen on large clumps of floating grass and other vegetation in the river, detached from the banks and slowly floating downstream.

Dow et al. (2018) listed I. decoratus melaenops from Riau Province as a first record, but at the time were unaware of the record in Gesriantuti et al. (2018) that had been published shortly before.

Macrogomphus Selys in Selys & Hagen, 1858

Macrogomphus decemlineatus Selys, 1878

Selected references:

Macrogomphus decemlineatus Selys, 1878 View in CoL ;—Selys 1878b: 418–419 (original description, type from Sumatra: South Sumatra);— Dow et al. 2018: 13 (first record from Riau).

Specimens collected. M1f: 1 ♂ ( RER23 _ GOM29 ; RER), 4 x 2023 ; 1 ♂ ( RER23 _ GOM30 ; BRIN), 4 x 2023; M 1m : 1 ♂ ( RER23 _ GOM9 ; RER), 16 ii 2023 ; 1 ♂ ( RER23 _ GOM10 ; BRIN), 16 ii 2023 ; 1 ♂ ( RER23 _ GOM11 ; UMRI), 16 ii 2023 .

Remarks. Macrogomphus decemlineatus is a relatively seldomly recorded species. Although certainly not confined to PSF and low pH waters, a significant percentage of the available records are from such habitats. It has also sometimes been found at streams in oil palm or at the oil palm—forest boundary. In the Kampar Peninsula it has so far only been found at two tributary streams of the Serkap River. In February 2023 in sunny conditions in the afternoon single males were found perched in small clearings on Sungai Sianyir, but in overcast conditions in October 2023 no individuals definitely of this species were seen at the same stream. Also in October 2023, but in sunny conditions, males were relatively common on Simpang Kanan, although the species had not been found there in February 2023.

Macromiidae

Epophthalmia Burmeister, 1839 View in CoL

Epophthalmia vittigera vittigera ( Rambur, 1842) View in CoL

Selected references:

Epophthamia vittigera ( Rambur, 1842) ;— Lieftinck 1931: 65 (first records from Sumatra: North and West Sumatra);— Dow et al. 2018: 13 (first record from Riau).

Specimens collected. M1a: 1 ♂ ( RER20 _ MAC1 About MAC ; RER), 18 i 2020 ; 1 ♂ ( RER20 _ MAC2 About MAC ; BRIN); 26 i 2020 ; 1 ♂ ( RER23 _ MAC2 About MAC ; BRIN), 12 ii 2023 ; 1 ♂ ( RER23 _ MAC4 About MAC ; UMRI), 4 x 2023; M5a : 1 ♂ ( RER23 _ MAC1 About MAC ; UMRI), 9 ii 2023 .

Remarks. Frequently found flying over broad, open areas of Sungai Serkap. Less common on the smaller Sungai Sangar.

Macromia Rambur, 1842

Macromia cincta Rambur, 1842 View in CoL

Selected references:

Macromia cincta Rambur, 1842 View in CoL ;—Selys 1889: 468 (first record from Sumatra: Bangka);— Karsch 1891: 245 (first record from mainland Sumatra: North Sumatra).

Specimens collected. M1a: 1 ♂ ( RER20 _ MAC3 About MAC ; RER), 15 i 2020 ; 1 ♂ ( RER20 _ MAC4 About MAC ; BRIN), 18 i 2020 ; 2 ♂♂ ( RER20 _ MAC5 About MAC , 7 About MAC ; UMRI), 19 i 2020 ; 1 ♂ ( RER20 _ MAC6 About MAC ; BRIN), 19 i 2020 ; 1 ♀ ( RER23 _ MAC3 About MAC ; RER), 12 ii 2023 ; 1 ♂ ( RER23 _ MAC5 About MAC ; BRIN), 4 x 2023 ; 1 ♂ ( RER23 _ MAC6 About MAC ; UMRI), 4 x 2023 .

Remarks. Recorded from Riau Province for the first time, abundant on Sungai Serkap. No specimen has been collected on Sungai Sangar but Macromia of the same size have been seen flying on that stream and are, in all probability, the same species.

Corduliidae Kirby, 1890

Hemicordulia Selys, 1870

Hemicordulia tenera Lieftinck, 1930 View in CoL

Selected references:

Hemicordulia tenera Lieftinck, 1930 View in CoL ;— Lieftinck 1954: 123 (first records from Sumatra: “northeast and east”).

Specimens collected. M5f: 1 ♀ ( RER23 _ COR1 About COR ; BRIN), 6 vi 2023 .

Remarks. Until now the vague records in Lieftinck (1954) have been the only ones of H. tenera from Sumatra. Although ‘east’ Sumatra might refer to Riau Province, it might not and in the absence of concrete evidence to the contrary we consider the record from the Kampar Peninsula to be the first from Riau Province. A single female was collected while it was flying over wet peat near a canal in forest.

Libellulidae

Acisoma Rambur, 1842 View in CoL

Acisoma panorpoides Rambur, 1842 View in CoL

Selected references:

Acisoma panorpoides Rambur, 1842 View in CoL ;—Selys 1889: 455 (first record from Sumatra: “ Sumatra ” without further details);— Ris 1927: 42 (first record from Riau).

Specimens collected. M1i: 1 ♀ ( RER20 _ LIB1 About LIB ; RER), 15 i 2020 ; M2e: 1 ♀ ( RER23 _ LIB1 About LIB ; BRIN), near dusk, 6 ii 2023 ; 1 ♂ ( RER23 _ LIB117 About LIB ; UMRI), 10 vi 2023 ; 1 ♀ ( RER23 _ LIB118 About LIB ; BRIN), 10 vi 2023 ; M7a: 1 ♂ ( RER20 _ LIB3 About LIB ; UMRI), 23 i 2020 ; M7b: 1 ♂ ( RER20 _ LIB5 About LIB ; BRIN), 23 i 2020 ; M7c: 1 ♂ ( RER20 _ LIB6 About LIB ; UMRI), 23 i 2020 ; M7d: 1 ♂ ( RER23 _ LIB2 About LIB ; UMRI), 19 ii 2023 ; M 7g: 1 ♂ ( RER20 _ LIB4 About LIB ; RER), 23 i 2020 ; 1 ♂ ( RER23 _ LIB3 About LIB ; BRIN), 19 ii 2023 ; M8a: 1 ♀ ( RER20 _ LIB2 About LIB ; BRIN), 16 i 2020 .

Remarks. Moderately common at open waters in the main part of the Kampar Peninsula.

Aethriamanta Kirby, 1889

Aethriamanta aethra Ris, 1912 View in CoL

Selected references:

Aethriamanta aethra Ris, 1912 View in CoL ;— Lieftinck 1954: 170 (first record from Sumatra: “ Sumatra ”).

Specimens collected. M7a: 2 ♂♂ ( RER20 _ LIB7 About LIB , 10 About LIB ; RER), 23 i 2020 ; 2 ♂♂ ( RER20 _ LIB8 About LIB , 11 About LIB ; BRIN), 23 i 2020 ; 1 ♂ ( RER20 _ LIB9 About LIB ; UMRI), 23 i 2020 ; 1 ♂ ( RER23 _ LIB4 About LIB ; BRIN), 19 ii 2023; M7b : 1 ♂ ( RER20 _ LIB12 About LIB ; UMRI), 23 i 2020 ; 1 ♂ ( RER20 _ LIB13 About LIB ; RER), 23 i 2020 .

Remarks. The vague record in Lieftinck (1954) was the only one of A. aethra from Sumatra until now, as in similar cases we treat our record as the first from Riau Province. This is generally a locally occurring species and in the Kampar Peninsula it was only found on acacia edge drains in one part of Meranti Estate.

Aethriamanta brevipennis brevipennis ( Rambur, 1842)

Selected references:

Aethriamanta brevipennis ( Rambur, 1842) View in CoL ;—Schmidt 1934: 385 (first record from Sumatra: South Sumatra).

Specimens collected. M2b: 1 ♂ ( RER20 _ LIB14 About LIB ; RER), 16 i 2020 ; 1 ♂ ( RER20 _ LIB15 About LIB ; BRIN), 16 i 2020 ; 1 ♂ ( RER20 _ LIB16 About LIB ; UMRI), 16 i 2020; M2e : 1 ♂ ( RER23 _ LIB119 About LIB ; BRIN), 10 vi 2023 ; 1 ♂ ( RER23 _ LIB120 About LIB ; UMRI), 10 vi 2023; M7a : 1 ♂ ( RER20 _ LIB17 About LIB ; RER), 23 i 2020 .

Remarks. Recorded from Riau Province for the first time. Found at drains and ponds with plentiful floating vegetation in the main part of the Kampar Peninsula.

Aethriamanta gracilis ( Brauer, 1878)

Selected references:

Brachydiplax gracilis ( Brauer, 1878) ;—Selys 1889: 456 (first record from Sumatra: “ Sumatra ”).

Specimens collected. M 1g: 1 ♂ ( RER23 _ LIB281 About LIB ; RER), 2 x 2023; M1p : 2 ♂♂ ( RER23 _ LIB5 About LIB (teneral), 8; BRIN), 12 ii 2023 ; 2 ♂♂ ( RER23 _ LIB6–7 About LIB ; RER), 12 ii 2023; M2e : 1 ♂ ( RER23 _ LIB121 About LIB ; BRIN), 10 vi 2023; M5a : 1 ♂ ( RER20 _ LIB20 About LIB ; UMRI), 25 i 2020 ; 1 ♂ ( RER20 _ LIB21 About LIB ; RER), 25 i 2020; M7a : 1 ♂ ( RER20 _ LIB18 About LIB ; RER), 23 i 2020 ; 1 ♂ ( RER20 _ LIB19 About LIB ; BRIN), 23 i 2020 ; 1 ♂ ( RER23 _ LIB10 About LIB ; RER), 19 ii 2023; M7d : 1 ♂ ( RER23 _ LIB9 About LIB ; UMRI), 19 ii 2023; M11a : 1 ♂ ( RER23 _ LIB122 About LIB ; UMRI), 11 vi 2023 ; 1 ♂ ( RER23 _ LIB123 About LIB ; RER), 11 vi 2023 ; 1 ♂ ( RER23 _ LIB124 About LIB ; BRIN), 11 vi 2023; M12a : 1 ♀ ( RER23 _ LIB280 About LIB ; UMRI), 29 ix 2023; P5d : 1 ♂ ( RER23 _ LIB125 About LIB ; UMRI), 21 vi 2023 ; 1 ♂ ( RER23 _ LIB278 About LIB ; RER), 22 ix 2023; P6b : 1 ♂ ( RER23 _ LIB279 About LIB ; BRIN), 23 ix 2023 .

Remarks. Recorded from Riau Province for the first time. Moderately common in open habitats in the Kampar Peninsula. The teneral male from Tasik Tengah (M1p) was found perched low in sparse emergent vegetation with its wings shut.

Agrionoptera Brauer, 1864

Agrionoptera insignis insignis ( Rambur, 1842) View in CoL

Selected references:

Agrionoptera insignis ( Rambur, 1842) View in CoL ;—Selys 1889: 461 (first record from Sumatra: “ Sumatra ”);— Dow et al. 2018: 14 (first records from Riau).

Specimens collected. M12d: 1 ♂ ( RER23 _ LIB126 About LIB ; RER), 18 vi 2023 ; 1 ♂ ( RER23 _ LIB127 About LIB ; BRIN), 18 vi 2023; P6f : 1 ♀ ( RER23 _ LIB282 About LIB ; UMRI), 25 ix 2023 .

Remarks. Seemingly uncommon in the Kampar Peninsula, perhaps surprisingly so for a species that had been considered to be “A littoral species, very abundant in the mangrove scrub and coastal swamps” Lieftinck (1954: 131) but see the comments on this species in Dow (2022).

Agrionoptera sexlineata Selys, 1879

Selected references:

Agrionoptera sexlineata Selys, 1879 View in CoL ;— Ris 1919: 1070 (first record from Sumatra: “Nordwest Sumatra ”);— Dow et al. 2018: 14 (first records from Riau).

Specimens collected. M10a: 1 ♂ ( RER23 _ LIB11 About LIB ; RER), 7 ii 2023 ; 1 ♀ ( RER23 _ LIB12 About LIB ; BRIN), 7 ii 2023 ; 1 ♂ ( RER23 _ LIB130 About LIB ; BRIN), 8 vi 2023; M12c : 1 ♀ ( RER23 _ LIB132 About LIB ; BRIN), 18 vi 2023; M12d : 1 ♂ ( RER23 _ LIB131 About LIB ; UMRI), 18 vi 2023; P1b : 1 ♀ ( RER23 _ LIB128 About LIB ; UMRI), 31 v 2023; P1d : 1 ♂ ( RER23 _ LIB129 About LIB ; RER), 2 vi 2023 .

Remarks. Not uncommon in PSF in the Kampar Peninsula.

Brachydiplax Brauer, 1868

Brachydiplax chalybea chalybea Brauer, 1868

Selected references:

Brachydiplax chalybea Brauer, 1868 View in CoL ;— Krüger 1902: 133 (first record from Sumatra: North Sumatra);— Ris 1927: 42 (first record from Riau).

Specimens collected. M1a: 1 ♂ ( RER23 _ LIB17 About LIB ; UMRI), 12 ii 2023; M1i : 1 ♂ ( RER20 _ LIB23 About LIB ; RER), 15 i 2020 ; 1 ♂ ( RER20 _ LIB24 About LIB ; BRIN), 15 i 2020; M2b : 1 ♂ ( RER20 _ LIB25 About LIB ; UMRI), 16 i 2020; M2c : 1 ♂ ( RER20 _ LIB26 About LIB ; RER), 16 i 2020; M2e : 1 ♂ ( RER23 _ LIB135 About LIB ; UMRI), 10 vi 2023 ; 1 ♂ ( RER23 _ LIB136 About LIB ; RER), 10 vi 2023; M3b : 1 ♂ ( RER20 _ LIB27 About LIB ; BRIN), 17 i 2020 ; 1 ♂ ( RER23 _ LIB15 About LIB ; UMRI), 10 ii 2023; M3c : 1 ♂ ( RER23 _ LIB13 About LIB ; UMRI), 10 ii 2023 ; 2 ♂♂ ( RER23 _ LIB14 About LIB , 16 About LIB ; BRIN), 10 ii 2023; M6 : 1 ♂ ( RER20 _ LIB32 About LIB ; BRIN), 23 i 2020; M7a : 1 ♂ ( RER20 _ LIB29 About LIB ; RER), 23 i 2020; M7b : 1 ♂ ( RER20 _ LIB30 About LIB ; BRIN), 23 i 2020 ; 1 ♂ ( RER20 _ LIB31 About LIB ; UMRI), 23 i 2020; M7d : 1 ♂ ( RER23 _ LIB18 About LIB ; BRIN), 19 ii 2023; M 7g : 1 ♂ ( RER23 _ LIB19 About LIB ; UMRI), 19 ii 2023; M9a : 1 ♂ ( RER20 _ LIB28 About LIB ; UMRI), 21 i 2020; M11a : 1 ♂ ( RER23 _ LIB137 About LIB ; BRIN), 11 vi 2023; M12d : 1 ♂ ( RER23 _ LIB138 About LIB ; UMRI), 18 vi 2023; M13b : 1 ♂ ( RER23 _ LIB287 About LIB ; UMRI), 29 ix 2023; M13c : 1 ♂ ( RER23 _ LIB288 About LIB ; BRIN), 29 ix 2023; P1a : 1 ♂ ( RER23 _ LIB286 About LIB ; BRIN), 24 ix 2023; P3c : 1 ♀ ( RER23 _ LIB133 About LIB ; RER), 30 v 2023; P4c : 1 ♂ ( RER23 _ LIB134 About LIB ; BRIN), 30 v 2023; P5a : 1 ♂ ( RER23 _ LIB139 About LIB ; RER), 21 vi 2023; P5d : 1 ♂ ( RER23 _ LIB140 About LIB ; BRIN), 21 vi 2023; P6a : 1 ♂ ( RER23 _ LIB283 About LIB ; UMRI), 22 ix 2023; P6b : 1 ♂ ( RER23 _ LIB285 About LIB ; UMRI), 23 ix 2023; P6c 1 ♂ ( RER23 _ LIB284 About LIB ; BRIN), 23 ix 2023 .

Remarks. Common in open habitats in the Kampar Peninsula.

Brachygonia ( Brauer, 1878)

Brachygonia oculata ( Brauer, 1878) View in CoL

Selected references:

Brachygonia oculata ( Brauer, 1878) View in CoL ;— Lieftinck 1935a: 15 (first record from Riau).

Microdiplax delicatula Selys, 1889 ;—Selys 1889: 459 (first record from Sumatra: Bangka).

Specimens collected. M1b: 1 ♂ ( RER20 _ LIB39 About LIB ; RER), 22 i 2020 ; 1 ♂ ( RER20 _ LIB40 About LIB ; BRIN), 22 i 2020 ; M1e: 1 ♂ ( RER20 _ LIB41 About LIB ; UMRI), 26 i 2020 ; 1 ♂ ( RER20 _ LIB42 About LIB ; BRIN), 26 i 2020 ; M1f: 1 ♀ ( RER20 _ LIB34 About LIB ; BRIN), 19 i 2020 ; M1h: 2 ♂♂ ( RER20 _ LIB35 About LIB , 38 About LIB ; UMRI), 19 i 2020 ; 1 ♂ ( RER20 _ LIB36 About LIB , RER), 19 i 2020 ; 1 ♂ ( RER20 _ LIB37 About LIB ; BRIN), 19 i 2020 ; M1j: 1 ♂ ( RER23 _ LIB295 About LIB ; RER), 2 x 2023 ; M 1m: 1 ♂ ( RER23 _ LIB293 About LIB ; BRIN), 1 x 2023 ; M1o: 1 ♂ ( RER23 _ LIB294 About LIB ; UMRI), 1 x 2023 ; M1q: 1 ♀ ( RER23 _ LIB32 About LIB ; UMRI), 16 ii 2023 ; 1 ♂ ( RER23 _ LIB46 About LIB ; RER), 16 ii 2023 ; M2a: 1 ♀ ( RER20 _ LIB33 About LIB ; RER), 16 i 2020 ; M4a: 1 ♂, 1 ♀ ( RER23 _ LIB26–27 About LIB ; UMRI), in tandem, 13 ii 2023 ; 1 ♂ ( RER23 _ LIB145 About LIB ; RER), 5 vi 2023 ; 1 ♂ ( RER23 _ LIB153 About LIB ; BRIN), 14 vi 2023 ; 1 ♂ ( RER23 _ LIB291 About LIB ; BRIN), 27 ix 2023 ; M4b: 2 ♂♂ ( RER23 _ LIB22–23 About LIB ; BRIN), 8 ii 2023 ; 1 ♂ ( RER23 _ LIB28 About LIB ; BRIN), 13 ii 2023 ; 2 ♂♂ ( RER23 _ LIB29–30 About LIB ; RER), 13 ii 2023 , leg. RER staff; 1 ♂ ( RER23 _ LIB31 About LIB ; BRIN), 13 ii 2023 , leg. RER staff; 1 ♂ ( RER23 _ LIB152 About LIB ; UMRI), 13 vi 2023 ; M4c: 1 ♂ ( RER23 _ LIB24 About LIB ; UMRI), 8 ii 2023 ; M4e: 1 ♂ ( RER23 _ LIB32 About LIB ; BRIN), 19 ii 2023 ; M5b: 1 ♂ ( RER23 _ LIB25 About LIB ; BRIN), 9 ii 2023 ; 1 ♂ ( RER23 _ LIB154 About LIB ; UMRI), 17 vi 2023 ; M5e: 1 ♀ ( RER23 _ LIB148 About LIB ; UMRI), 6 vi 2023 ; M5f: 1 ♂, 1 ♀ ( RER23 _ LIB146–147 About LIB ; BRIN), in tandem, 6 vi 2023 ; M 5g: 1 ♂ ( RER23 _ LIB292 About LIB ; UMRI), 28 ix 2023 ; M10a: 2 ♂♂ ( RER23 _ LIB20–21 About LIB ; UMRI), 7 ii 2023 ; 1 ♂ ( RER23 _ LIB149 About LIB ; BRIN), 8 vi 2023 ; M11b: 1 ♂ ( RER23 _ LIB150 About LIB ; UMRI), 11 vi 2023 ; M11c: 1 ♂ ( RER23 _ LIB151 About LIB ; BRIN), 11 vi 2023 ; M12b: 1 ♂ ( RER23 _ LIB156 About LIB ; UMRI), 18 vi 2023 ; M12d: 1 ♂ ( RER25 _ LIB155 About LIB ; BRIN), 18 vi 2023 ; P1b: 1 ♂ ( RER23 _ LIB142 About LIB ; RER), 31 v 2023 ; 1 ♂ ( RER23 _ LIB143 About LIB ; BRIN), 31 v 2023 ; 1 ♂ ( RER23 _ LIB144 About LIB ; UMRI), 2 vi 2023 ; P1c: 1 ♂ ( RER23 _ LIB289 About LIB ; BRIN), 24 ix 2023 ; P3d: 1 ♂ ( RER23 _ LIB141 About LIB ; UMRI), 30 v 2023 ; P6f: 1 ♂ ( RER23 _ LIB290 About LIB ; UMRI), 25 ix 2023 .

Remarks. Although quite regularly found in other habitats, B. oculata is primarily a swamp forest species, usually common in PSF and abundant in much of the main part of the Kampar Peninsula.

Brachygonia puella Lieftinck, 1937

Selected references:

Brachygonia puella Lieftinck, 1937 View in CoL ;— Lieftinck 1937: 105–107, fig. 25 (original description from Belitung).

Specimens collected. M1r: 1 ♂ ( RER23 _ LIB34 About LIB ; RER), 15 ii 2023 ; 2 ♂♂ ( RER23 _ LIB35 About LIB , 37 About LIB ; BRIN), 15 ii 2023 ; 1 ♂ ( RER23 _ LIB36 About LIB ; UMRI), 15 ii 2023 .

Remarks. Recorded from mainland Sumatra for the first time, previously only known from Belitung and Borneo. A population of B. puella was found at a single section of flooded but rather open forest at the upper part of Sungai Serkap. Searches were made for the species at apparently similar sites in the same part of Sungai Serkap without success.

Brachythemis Brauer, 1868

Brachythemis contaminata ( Fabricius, 1793) View in CoL

Selected references:

Brachythemis contaminata ( Fabricius, 1793) View in CoL ;— Karsch 1891: 245 (first record from Sumatra: North Sumatra);— Gesriantuti et al. 2018: 200 (first record from Riau).

Specimens collected. P4a: 1 ♂ ( RER23 _ LIB157 About LIB ; RER), 31 v 2023 ; P5d: 1 ♂ ( RER23 _ LIB158 About LIB ; BRIN), 21 vi 2023 ; 1 ♂ ( RER23 _ LIB296 About LIB ; UMRI), immature, 22 ix 2023 ; 1 ♀ ( RER23 _ LIB297 About LIB ; BRIN), immature, 22 ix 2023 ; P6b: 1 ♂ ( RER23 _ LIB298 About LIB ; UMRI), 23 ix 2023 .

Remarks. Only found around ponds at the base of the Kampar Peninsula.

Camacinia Kirby, 1889

Camacinia gigantea (Brauer, 1867)

Selected references:

Camacinia gigantea (Brauer, 1867) View in CoL ;— Karsch 1891: 245 (first record from Sumatra: North Sumatra).

Specimens collected. M5a: 1 ♀ ( RER23 _ LIB299 About LIB ; BRIN), 28 ix 2023 ;

Remarks. Recorded from Riau Province for the first time. In addition to the female collected, two males were seen at location P6c on 23 ix 2023. The female was collected while flying over the main channel of Sungai Sangar and might have been far from its breeding habitat.

Chalybeothemis Lieftinck, 1933

Chalybeothemis chini Dow, Choong & Orr, 2007 View in CoL

Selected references:

Chalybeothemis chini Dow, Choong & Orr, 2007 View in CoL ;— Dow et al. 2007: 171, 173–175, Figs 1a View FIGURE 1 , 2a View FIGURE 2 , 3a View FIGURE 3 , 4a View FIGURE 4 , 5a View FIGURE 5 , 6a View FIGURE 6 , 7a, 8a, 9a View FIGURES 7–11 , Table 1 (original description from Pahang).

Specimens collected. M12a: 1 ♂ ( RER23 _ LIB159 About LIB ; RER), 18 vi 2023 ; 1 ♂ ( RER23 _ LIB301 About LIB ; UMRI), 29 ix 2023 ; 1 ♂ ( RER23 _ LIB302 About LIB ; RER), 29 ix 2023; P6b : 1 ♂ ( RER23 _ LIB300 About LIB ; BRIN), 23 ix 2023 .

Remarks. Recorded from Indonesia for the first time, until now C. chini had only been known from a few sites in Peninsular Malaysia, with records from Pahang ( Dow et al. 2007), Kelantan ( Choong et al. 2017), Selangor ( Dow & Ng 2020) and Terengganu ( Choong et al. 2020). Found in the largely open lower part of Sungai Kutup where it occurred together with Chalybeothemis fluviatilis Lieftinck, 1933 , a single male was found at a pond at the base of the Kampar Peninsula.

Chalybeothemis fluviatilis Lieftinck, 1933

Selected references:

Chalybeothemis fluviatilis Lieftinck, 1933 View in CoL ;— Lieftinck 1954: 143 (first record from Sumatra: Belitung).

Diplacodes trivalis ( Rambur, 1842) ;— Pujiastuti et al. 2017: 3, Fig. 3g View FIGURE 3 (?part, first record from mainland Sumatra: South Sumatra).

Specimens collected. M1a: 1 ♂ ( RER20 _ LIB45 About LIB ; UMRI), 15 i 2020 ; 1 ♂ ( RER20 _ LIB46 About LIB ; RER), 19 i 2020 ; 1 ♂ ( RER23 _ LIB47 About LIB ; UMRI), 12 ii 2023; M1c : 1 ♂ ( RER20 _ LIB43 About LIB ; RER), 15 i 2020 ; 1 ♂ ( RER20 _ LIB44 About LIB ; BRIN), 15 i 2020; M 1g : 1 ♂ ( RER23 _ LIB54 About LIB ; UMRI), 26 i 2020 ; 1 ♂ ( RER20 _ LIB55 About LIB ; RER), 26 i 2020 ; 1 ♂ ( RER23 _ LIB310 About LIB ; UMRI), 2 x 2023; M1j : 1 ♂ ( RER23 _ LIB309 About LIB ; BRIN), 2 x 2023; M1l : 1 ♂ ( RER23 _ LIB48 About LIB ; BRIN), 15 ii 2023; M1p : 1 ♂ ( RER23 _ LIB42 About LIB ; RER), 12 ii 2023 ; 2 ♂♂ ( RER23 _ LIB43 About LIB , 45 About LIB ; BRIN), 12 ii 2023 ; 1 ♂ ( RER23 _ LIB44 About LIB ; UMRI), 12 ii 2023; M5a : 3 ♂♂ ( RER20 _ LIB47 About LIB , 49 About LIB , 51 About LIB ; BRIN), 20 i 2020 ; 2 ♂♂ ( RER20 _ LIB48 About LIB , 50 About LIB ; UMRI), 20 i 2020 ; 1 ♂ ( RER20 _ LIB52 About LIB ; UMRI), 25 i 2020 ; 1 ♀ ( RER20 _ LIB53 About LIB ; BRIN), 25 i 2020 ; 1 ♂ ( RER23 _ LIB38 About LIB ; RER), 9 ii 2023 ; 2 ♂♂ ( RER23 _ LIB39 About LIB , 41 About LIB ; BRIN), 9 ii 2023 ; 1 ♂ ( RER23 _ LIB40 About LIB ; UMRI), 9 ii 2023 ; 1 ♂ ( RER23 _ LIB160 About LIB ; RER), 6 vi 2023; M12a : 3 ♂♂ ( RER23 _ LIB306–308 About LIB ; RER), 29 ix 2023; P5d : 1 ♂ ( RER23 _ LIB303 About LIB ; RER), 22 ix 2023 ; 1 ♂ ( RER23 _ LIB304 About LIB ; BRIN), 22 ix 2023 ; 1 ♂ ( RER23 _ LIB305 About LIB ; UMRI), 22 ix 2023 .

Remarks. Recorded from Riau Province for the first time. There is no previously published record from mainland Sumatra of C. fluviatilis but Pujiastuti et al. (2017) list Diplacodes trivialis ( Rambur, 1842) with a photograph (their Fig. 3g View FIGURE 3 ) that clearly shows C. fluviatilis rather than the Diplacodes , so at least part of their records are actually of C. fluviatilis . Common on open parts of the streams and rivers in the main part of the Kampar Peninsula, as it often is in low pH waters. Quite abundant on the large pond at location P5d in September 2023 but not even seen there in June 2023.

Cratilla Kirby, 1900

Cratilla lineata lineata ( Brauer, 1878) View in CoL

Selected references:

Cratilla lineata ( Brauer, 1878) View in CoL ;— Dow et al. 2018: 14 (first records from Riau).

Orthemis lineata Brauer, 1878 View in CoL ;—Selys 1889: 462 (first record from Sumatra: West Sumatra).

Specimens collected. P6c: 1 ♀ ( RER23 _ LIB311 About LIB ; UMRI), 23 ix 2023; P 6g : 1 ♂ ( RER23 _ LIB312 About LIB ; RER), 25 ix 2023 .

Remarks. Only found at the base of the Kampar Peninsula, not on the peat soils.

Crocothemis Brauer, 1868

Crocothemis servilia servilia ( Drury, 1773) View in CoL

Selected references:

Crocothemis servilia ( Drury, 1773) View in CoL ;—Selys 1889: 468 (first record from Sumatra: West Sumatra);— Ris 1927: 43 (first record from Riau).

Specimens collected. M 7g: 1 ♂ ( RER20 _ LIB56 About LIB ; RER), 23 i 2020 ; 1 ♂ ( RER23 _ LIB49 About LIB ; BRIN), 19 ii 2023 ; 1 ♂ ( RER23 _ LIB161 About LIB ; UMRI), 15 vi 2023; P6a : 1 ♂ ( RER23 _ LIB313 About LIB ; RER), 22 ix 2023 .

Remarks. Found at a rain-fed pond (lacking the black water seen almost everywhere else on the peat soils) beside the Kampar River in the main part of the peninsula and one site at the base of the peninsula.

Diplacodes Kirby, 1889

Diplacodes nebulosa ( Fabricius, 1793) View in CoL

Selected references:

Diplacodes nebulosa ( Fabricius, 1793) View in CoL ;— Ris 1927: 42 (first record from Sumatra: Riau and West Sumatra).

Specimens collected. P5d: 1 ♂ ( RER23 _ LIB314 About LIB ; UMRI), 22 ix 2023 .

Remarks. A few individuals were seen at the large pond at location P5d on both occasions it was visited, with a single male collected on the second visit.

Diplacodes trivialis ( Rambur, 1842)

Selected references:

Diplax trivialis ( Rambur, 1842) ;—Selys 1889: 454 (first records from Sumatra: West Sumatra).

Diplacodes trivialis ( Rambur, 1842) View in CoL ;— Gesriantuti et al. 2018: 201 (first record from Riau).

Specimens collected. M 7g: 1 ♂ ( RER20 _ LIB57 About LIB ; RER), 23 i 2020 ; 1 ♂ ( RER23 _ LIB50 About LIB ; BRIN), 19 ii 2023 .

Remarks. As with I. decoratus melaenops Dow et al. (2018) listed D. trivialis from Riau Province as a first record, in ignorance of Gesriantuti et al. (2018) that had been published shortly before. Apparently not common in the Kampar Peninsula, with records from only one site.

Hydrobasileus Kirby, 1889

Hydrobasileus croceus (Brauer, 1867)

Selected references:

Hydrobasileus croceus (Brauer, 1867) View in CoL ;— Karsch 1891: 245 (first record from Sumatra: North Sumatra);— Dow et al. 2018: 15 (first record from Riau).

Specimens collected. M8b: 1 ♀ ( RER20 _ LIB58 About LIB ; UMRI), attracted to lights in building, 24 i 2020 .

Remark. More common in the Kampar Peninsula than the single record above suggests, seen flying over large, open drains on many occasions.

Lathrecista Kirby, 1889

Lathrecista asiatica asiatica ( Fabricius, 1798) View in CoL

Selected references:

Lathrecista asiatica ( Fabricius, 1798) View in CoL ;— Dow et al. 2018: 15 (first records from Riau).

Lathrecista difficilis (Selys, 1879) (?);—Selys 1889: 462 (part of first records from Sumatra: Bangka).

Lathrecista simulans (Selys, 1879) ;—Selys 1889: 462 (part of first records from Sumatra: North Sumatra).

Specimens collected. M3c: 1 ♂, 1 ♀ ( RER20 _ LIB59 About LIB , 62 About LIB ; RER), 17 i 2020 ; 1 ♂, 1 ♀ ( RER20 _ LIB60 About LIB , 63 About LIB ; BRIN), 17 i 2020 ; 1 ♂ ( RER20 _ LIB61 About LIB ; UMRI), 17 i 2020 ; 1 ♂ ( RER23 _ LIB51 About LIB ; UMRI), 10 ii 2023 ; 1 ♂ ( RER23 _ LIB52 About LIB ; BRIN), 10 ii 2023 .

Remarks. Selys (1889) lists L. difficilis from Banca (Bangka), this name is now considered a junior synonym of the neo-tropical Anatya guttata ( Erichson, 1848) . The record from Bangka obviously cannot refer to A. guttata and given that Selys placed it in Lathrecista we assume here that it refers to L. asiatica . Quite common under rubber trees at a site in the main part of the Kampar Peninsula.

Lyriothemis Brauer, 1868

Lyriothemis sp.

Specimens collected. M4b: 1 ♀ ( RER23 _ LIB162 About LIB ; RER), 13 vi 2023 .

Remarks. Although four species of Lyriothemis have been recorded in Sumatra ( L. biappendiculata (Selys, 1878) , L. cleis Brauer, 1868 , L. magnificata (Selys, 1878) and L. salva Ris, 1927 ), none had been recorded in Riau Province until now. The single female collected is certainly not L. biappendiculata , is atypically coloured for L. cleis and is probably L. magnificata . We are not aware of any previous records of this genus definitely from PSF but, for instance, there is an old female specimen of L. magnificata from the Matang Road in Sarawak in the collection of the Sarawak Museum ( Dow & Morris 2021), much of the surrounds of the Matang Road near to Kuching was originally PSF; there are also records of L. cleis from the surrounds of Tasik Bera ( Norma-Rashid et al. 2001) and Tasik Chini ( Kalkman 2004) in Pahang that could be from PSF. The female from the Kampar Peninsula was collected whilst it was flying around in a small clearing made by a treefall ( L. cleis is quite often found in such situations in other types of forest).

Nannophya Rambur, 1842

Nannophya pygmaea Rambur, 1842 View in CoL

Selected references:

Nannophya pygmaea Rambur, 1842 View in CoL ;—Selys 1889: 460 (first record from Sumatra: North Sumatra);— Lieftinck 1935a: 15 (first record from Riau).

Specimens collected. M 1g: 1 ♂ ( RER23 _ LIB317 About LIB ; BRIM), 2 x 2023 ; M1j: 1 ♂ ( RER23 _ LIB316 About LIB ; RER), 2 x 2023 ; M1p: 1 ♂ ( RER23 _ LIB54 About LIB ; RER), 12 ii 2023 ; M1r: 1 ♂, 1 ♀ ( RER23 _ LIB56 About LIB , 57 About LIB ; UMRI), 15 ii 2023 ; M4d: 1 ♂ ( RER23 _ LIB53 About LIB ; UMRI), 8 ii 2023 ; M4e: 1 ♂ ( RER23 _ LIB55 About LIB ; BRIN), 13 ii 2023 ; 1 ♂ ( RER23 _ LIB315 About LIB ; UMRI), 27 ix 2023 ; M5a: 1 ♂ ( RER20 _ LIB64 About LIB ; RER), 20 i 2020 ; M5d: 2 ♂♂ ( RER20 _ LIB65–66 About LIB ), 23 i 2020 ; M5e: 1 ♂ ( RER23 _ LIB163 About LIB ; RER), 6 vi 2023 ; M11a: 1 ♂ ( RER23 _ LIB164 About LIB ; BRIN), 11 vi 2023 .

Remarks. Moderately common in the main part of the Kampar Peninsula.

Nannophyopsis Lieftinck, 1935

Nannophyopsis chalcosoma Lieftinck, 1935

Selected references:

Nannophyopsis chalcosoma Lieftinck, 1935 View in CoL ;— Lieftinck 1935b: 185–188, figs. 4–6 (original description from Belitung);—Dow et al. 2024: 52 (summary of distribution).

Specimens collected. P1c: 1 ♀ ( RER23 _ LIB165 About LIB ; BRIN), teneral, 2 vi 2023 .

Remarks. This is the first record of Nannophyopsis chalcosoma from mainland Sumatra, until now all records of N. chalcosoma had been from Belitung or Borneo. A single teneral female was collected while perched at head height over the ‘stream’ at Tasik Anggrek.

Nesoxenia Kirby, 1889

Nesoxenia lineata (Selys, 1879)

Selected references:

Agrionoptera lineata Selys, 1879 ;—Selys 1889: 461 (part of first record from Sumatra: Bangka).

Agrionoptera mysis Selys, 1878 ;—Selys 1889: 461 (part of first record from Sumatra: Bangka).

Nesoxenia lineata (Selys, 1879) View in CoL ;— Dow et al. 2018: 15 (first record from Riau).

Specimens collected. M3d: 1 ♂ ( RER20 _ LIB22 About LIB ; BRIN), 17 i 2020; M4b : 1 ♂ ( RER23 _ LIB58 About LIB ; UMRI), 13 ii 2023 .

Remarks. Only recorded twice in the Kampar Peninsula but likely to be more common there than these records suggest since it always occurs at low densities and can be wary so it is often under-recorded.

Neurothemis Brauer, 1867

Neurothemis fluctuans ( Fabricius, 1793) View in CoL

Selected references:

Neurothemis fluctuans ( Fabricius, 1793) View in CoL ;—Selys 1889: 452 (first records from Sumatra: North Sumatra (mainland and Nias);— Ris 1927: 42 (first records from Riau).

Specimens collected. M 1g: 1 ♀ ( RER20 _ LIB75 About LIB ; BRIN) , 26 i 2020; M1i: 1 ♂ ( RER20 _ LIB67 About LIB ; RER) , 15 i 2020; M2a: 1 ♂ ( RER20 _ LIB68 About LIB ; BRIN) , 16 i 2020; 1 ♂ ( RER20 _ LIB69 About LIB ; UMRI) , 16 i 2020; M2e: 1 ♂ ( RER23 _ LIB59 About LIB ; UMRI) , just before dusk, 6 ii 2023; 1 ♂ ( RER23 _ LIB60 About LIB ; RER) , just before dusk, 6 ii 2023; 2 ♂♂ ( RER23 _ LIB171 About LIB , 174 About LIB ; UMRI) , 10 vi 2023; 1 ♂ ( RER23 _ LIB172 About LIB ; RER) , 10 vi 2023; 2 ♂♂ ( RER23 _ LIB173 About LIB , 175 About LIB ; BRIN) , 10 vi 2023; M2f: 1 ♀ ( RER23 _ LIB77 About LIB ; BRIN) , at lights after 7 PM, 14 ii 2023, leg. Eco Camp canteen staff; 1 ♀ ( RER23 _ LIB176 About LIB ; UMRI) , at lights at ca. 7 PM, 14 vi 2023, leg. Eco Camp canteen staff; M3b: 1 ♂ ( RER20 _ LIB70 About LIB ; RER) , 17 i 2020; 1 ♂ ( RER23 _ LIB63 About LIB ; BRIN) , 10 ii 2023; 1 ♀ ( RER23 _ LIB64 About LIB ; UMRI) , 10 ii 2023; M3c: 1 ♂, 1 ♀ ( RER20 _ LIB71–72 About LIB ; BRIN) , in tandem, 17 i 2020; 3 ♂♂, 3 ♀♀ ( ♂♂: RER23 _ LIB65 About LIB , 71 About LIB , 73 About LIB , ♀♀: RER23 _ LIB67 About LIB , 69 About LIB , 75 About LIB ; BRIN) , 10 ii 2023, leg. RER staff; 2 ♂♂, 3 ♀♀ ( ♂♂: RER23 _ LIB66 About LIB , 72 About LIB , ♀♀: RER23 _ LIB68 About LIB , 70 About LIB , 74 About LIB ; UMRI) , 10 ii 2023, leg. RER staff; M4e: 1 ♂ ( RER23 _ LIB76 About LIB ; UMRI) , 13 ii 2023; M4f: 1 ♂ ( RER23 _ LIB170 About LIB ; BRIN) , 5 vi 2023; M5d: 1 ♀ ( RER20 _ LIB74 About LIB ; RER) , 23 i 2020; M7b: 1 ♂ ( RER20 _ LIB73 About LIB ; UMRI) , 23 i 2020; M 7g: 1 ♂ ( RER23 _ LIB78 About LIB ; UMRI) , 19 ii 2023; M10b: 1 ♀ ( RER23 _ LIB62 About LIB ; UMRI) , 7 ii 2023; M10c: 1 ♂ ( RER23 _ LIB61 About LIB ; BRIN) , 7 ii 2023; M12a: 1 ♂ ( RER23 _ LIB178 About LIB ; UMRI) , 18 vi 2023; M12c: 1 ♂ ( RER23 _ LIB177 About LIB ; BRIN) , 18 vi 2023; P1e: 1 ♂ ( RER23 _ LIB167 About LIB ; BRIN) , 2 vi 2023; P4a: 1 ♂ ( RER23 _ LIB168 About LIB ; UMRI) , 2 vi 2023; 1 ♂ ( RER23 _ LIB169 About LIB ; RER) , 2 vi 2023; P4b: 1 ♂ ( RER23 _ LIB166 About LIB ; RER) , 31 v 2023; P5a: 1 ♂ ( RER23 _ LIB179 About LIB ; BRIN) , 21 vi 2023; 1 ♂ ( RER23 _ LIB180 About LIB ; UMRI) , 21 vi 2023; 1 ♂ ( RER23 _ LIB320 About LIB ; RER) , 22 ix 2023; P5b: 1 ♂ ( RER23 _ LIB181 About LIB ; BRIN) , 21 vi 2023; P5d: 1 ♂ ( RER _ LIB319 About LIB ; RER) , 22 ix 2023; P5e: 1 ♂ ( RER23 _ LIB318 About LIB ; UMRI) , 22 ix 2023; P6c: 1 ♂ ( RER23 _ LIB322 About LIB ; RER) , 23 ix 2023; P6e: 1 ♂ ( RER23 _ LIB321 About LIB ; RER) , 23 ix 2023;

Remarks. Very common in open habitats throughout the Kampar Peninsula.

Neurothemis fulvia ( Drury, 1773)

Selected references:

Neurothemis sophronia Drury, 1773 View in CoL ;— Krüger 1902: 126 (first record from Sumatra: North Sumatra). Specimens collected. P3c: 1 ♂ (RER23_LIB182; UMRI), 30 v 2023.

Remarks. Recorded from Riau Province for the first time, the single male collected was the only individual of this species seen. There are only a few records of N. fulvia from Sumatra, apart from the first record listed above (of three males), Lieftinck (1935a) listed five specimens from Jambi and South Sumatra and Seehausen & Dow (2016) listed a single old specimen from Lampung; in total only 10 specimens of the species have been recorded from Sumatra, all from the mainland.

Orchithemis Brauer, 1878

Orchithemis pruinans (Selys, 1878)

Selected references:

Calothemis pruinans Selys, 1878 ;—Selys 1878a: 308 (original description from Bangka).

Specimens collected. M1f: 1 ♂ ( RER23 _326; RER), 4 x 2023; M 1m : 1 ♂ ( RER23 _ LIB79 About LIB ; RER), 16 ii 2023 ; 1 ♂ ( RER23 _ LIB80 About LIB ; BRIN), 16 ii 2023 ; 1 ♂ ( RER23 _ LIB81 About LIB ; UMRI), 16 ii 2023 ; 1 ♂ ( RER23 _ LIB324 About LIB ; BRIN), 1 x 2023 ; 1 ♂ ( RER23 _ LIB325 About LIB ; UMRI), 1 x 2023; M5a : 1 ♂ ( RER23 _ LIB323 About LIB ; RER), 28 ix 2023; M5f : 1 ♂ ( RER23 _ LIB185 About LIB ; UMRI), 6 vi 2023; P1b : 1 ♂ ( RER23 _ LIB183 About LIB ; RER), 31 v 2023; P1c : 1 ♂ ( RER23 _ LIB184 About LIB ; BRIN), 2 vi 2023 .

Remarks. Recorded from Riau Province for the first time, almost all Sumatran records of O. pruinans have been from Bangka-Belitung. Found at and around smaller forest streams and stream-like canals in PSF in the Kampar Peninsula. This is another species that, while certainly not confined to PSF, thrives in PSF where suitable microhabitats exist.

Orchithemis pulcherrima Brauer, 1878

Selected references:

Orchithemis pulcherrima Brauer, 1878 View in CoL ;—Selys 1889: 460 (first record from Sumatra: Bangka);— Karsch 1891: 245 (first record from mainland Sumatra: North Sumatra);— Dow et al. 2018: 16 (first record from Riau).

Specimens collected. M4a: 1 ♂ ( RER23 _ LIB192 About LIB ; RER), 5 vi 2023; M5f : 2 ♂♂ ( RER23 _ LIB193 About LIB , 196 About LIB ; BRIN), 6 vi 2023 ; 1 ♂ ( RER23 _ LIB194 About LIB ; UMRI), 6 vi 2023 ; 1 ♂ ( RER23 _ LIB195 About LIB ; RER), 6 vi 2023; M 5g : 1 ♂ ( RER23 _ LIB327 About LIB ; UMRI), 28 ix 2023; P1b : 1 ♂ ( RER23 _ LIB188 About LIB ; UMRI), 31 v 2023 ; 1 ♂ ( RER23 _ LIB189 About LIB ; RER), 31 v 2023 ; 1 ♂ ( RER2 _ LIB190 About LIB ; BRIN), 2 vi 2023; P1c : 1 ♂ ( RER23 _ LIB191 About LIB ; UMRI), 2 vi 2023; P1d : 1 ♀ ( RER23 _ LIB186 About LIB ; RER), 30 v 2023 ; 1 ♀ ( RER23 _ LIB187 About LIB ; BRIN), 30 v 2023 .

Remarks. Although eventually recorded from six locations in the Kampar Peninsula, O. pulcherrima was not found at all during the surveys in January 2020 and February 2023. This is generally a common species in swamp forest so its apparent absence early in the year is curious but could be an artefact of sampling effort.

Orthetrum Newman, 1833

Orthetrum chrysis (Selys, 1891)

Selected references:

Orthetrum chrysis (Selys, 1891) View in CoL ;— Krüger 1902: 144 (first records from Sumatra: North Sumatra);— Dow et al. 2018: 16 (first records from Riau).

Specimens collected. M2c: 1 ♂ ( RER20 _ LIB76 About LIB ; RER), 16 i 2020; M3b : 1 ♀ ( RER20 _ LIB77 About LIB ; BRIN), 17 i 2020 ; 1 ♂ ( RER23 _ LIB83 About LIB ; UMRI), 10 ii 2023; M3e : 1 ♂ ( RER20 _ LIB79 About LIB ; RER), 24 i 2020; M4d : 1 ♂ ( RER23 _ LIB82 About LIB ; BRIN), 8 ii 2023; M7b : 1 ♂ ( RER20 _ LIB78 About LIB ; UMRI), 23 i 2020; M12a : 1 ♂ ( RER23 _ LIB200 About LIB ; BRIN), 18 vi 2023; M13b : 1 ♂ ( RER23 _ LIB330 About LIB ; RER), 29 ix 2023; P1a : 1 ♂ ( RER23 _ LIB328 About LIB ; UMRI), 24 ix 2023; P1c : 1 ♂ ( RER23 _

LIB199 About LIB ; UMRI), 2 vi 2023; P1e: 1 ♂ ( RER23 _ LIB197 About LIB ; RER), immature, 30 v 2023; 1 ♂ ( RER23 _ LIB198 About LIB ; BRIN), 30 v 2023; P6f: 1 ♂ ( RER23 _ LIB329 About LIB ; RER), 25 ix 2023 .

Remarks. Fairly common throughout the Kampar Peninsula. The immature male from location P1e was being consumed by a female of Orthetrum sabina when it was collected on 30 v 2023.

Orthetrum glaucum (Brauer, 1865)

Selected references:

Libellula glauca Brauer, 1865 ;—Selys 1889: 464 (first record from Sumatra: North Sumatra).

Orthetrum glaucum (Brauer, 1865) ;—Steinhoff et al. 2016 (first record from Riau).

Specimens collected. P6f: 1 ♂ ( RER23 _ LIB331 About LIB ; UMRI), 25 ix 2023 .

Remarks. Seemingly absent from the main part of the Kampar Peninsula, with just a single record from the base of the peninsula made during our surveys.

Orthetrum luzonicum (Brauer, 1868)

Selected references:

Libellula luzonica Brauer, 1868 ;—Selys 1889: 464 (first record from Sumatra: West Sumatra).

Specimens collected. P5a: 1 ♂ ( RER23 _ LIB201 About LIB ; BRIN), 21 vi 2023 ; 1 ♂ ( RER23 _ LIB202 About LIB ; UMRI), 21 vi 2023 .

Remarks. Orthetrum luzonicum had not been recorded from Riau Province prior to this.A few individuals were present in marshy sections with long emergent grasses at the margins of the stream in the afternoon in June 2023; no individuals were recorded on a morning visit to this site in September 2023, but higher water levels made the exact parts of the stream where it was found in June very difficult to access on that visit.

Orthetrum sabina sabina ( Drury, 1773)

Selected references:

Lepthemis sabina ( Drury, 1773) ;—Selys 1889: 455 (first records from Sumatra: North Sumatra (including Nias) and West Sumatra).

Orthetrum sabina ( Drury, 1773) View in CoL ;— Ris 1927: 40 (first record from Riau).

Specimens collected. M2b: 1 ♂ ( RER20 _ LIB81 About LIB ; BRIN), 16 i 2020 ; M2e: 1 ♂ ( RER23 _ LIB208 About LIB ; UMRI), 10 vi 2023 ; M3a: 1 ♀ ( RER20 _ LIB82 About LIB ; UMRI), 17 i 2020 ; M3e: 1 ♀ ( RER20 _ LIB84 About LIB ; BRIN), 24 i 2020 ; M7d: 1 ♂ ( RER23 _ LIB85 About LIB ; BRIN), 19 ii 2023 ; M 7g: 1 ♂ ( RER20 _ LIB83 About LIB ; RER), 23 i 2020 ; 1 ♂ ( RER23 _ LIB86 About LIB ; UMRI), 19 ii 2023 ; M8a: 1 ♂ ( RER20 _ LIB80 About LIB ; RER), 16 i 2020 ; M10b: 1 ♂ ( RER23 _ LIB84 About LIB ; UMRI), 7 ii 2023 ; M13c: 1 ♂ ( RER23 _ LIB334 About LIB ; UMRI), 29 ix 2023 ; P1e: 1 ♀ ( RER23 _ LIB205 About LIB ; BRIN), 30 v 2023 ; P3b: 1 ♂, 1 ♀ ( RER23 _ LIB203–204 About LIB ; RER), in tandem, 30 v 2023 ; P3c: 1 ♂ ( RER23 _ LIB206 About LIB ; UMRI), 30 v 2023 ; P4a: 1 ♂ ( RER23 _ LIB207 About LIB ; BRIN), 31 v 2023 ; P5a: 1 ♂ ( RER23 _ LIB209 About LIB ; RER), 29 vi 2023 ; P5d: 1 ♂ ( RER23 _ LIB332 About LIB ; UMRI), 22 ix 2023 ; P6e: 1 ♂ ( RER23 _ LIB333 About LIB ; BRIN), 23 ix 2023 .

Remarks. In addition to the specimen records above, O. sabina was very frequently seen at open drains around the plantations in the Kampar Peninsula, and around muddy pools on and beside roads, often in company with Pantala flavescens ( Fabricius, 1798) in the latter situation. On at least two occasions, while sitting in a vehicle behind a lorry loaded with acacia logs, the first author observed O. sabina attempting to perch on the logs while the lorry was moving.

Orthetrum testaceum testaceum ( Burmeister, 1839)

Selected references:

Libellula testacea Burmeister, 1839 ;— Burmeister 1839: 859 (original description from Java);—Selys 1889: 463 (first record from Sumatra: first records from Sumatra: North Sumatra (including Nias) and West Sumatra).

Orthetrum testaceum ( Burmeister, 1839) View in CoL ;— Ris 1927: 40 (first record from Riau).

Specimens collected. P4b: 1 ♂ ( RER23 _ LIB210 About LIB ; RER), 31 v 2023; P5a : 1 ♂ ( RER23 _ LIB211 About LIB ; BRIN), 21 vi 2023; P6e : 1 ♂ ( RER23 _ LIB335 About LIB ; UMRI), 23 ix 2023 .

Remarks. Probably much more common in the Kampar Peninsula than the records above suggest, this species was seen in passing at muddy puddles on roads and at drains in acacia on a number of occasions.

Pantala Hagen, 1861

Pantala flavescens ( Fabricius, 1798) View in CoL

Selected references:

Pantala flavescens ( Fabricius, 1798) View in CoL ;— Selys 1889: 449 (first records from Sumatra: West Sumatra and Nias ( North Sumara ));— Ris 1927: 44 (first record from Riau) .

Specimens collected. M1i: 1 ♀ ( RER20 _ LIB85 About LIB ; BRIN), flying over road, 18 i 2020 ; M12c: 1 ♂ ( RER23 _ LIB212 About LIB ; UMRI), 18 vi 2023 .

Remarks. Pantala flavescens is much more common in the Kampar Peninsula than the specimen records suggest, during the surveys it was seen flying over roads and large drainage ditches during sunny weather almost everywhere visited in the peninsula.

Pornothemis Krüger, 1902

Pornothemis sp. cf. serrata Krüger, 1902 View in CoL

Selected references for Pornothemis serrata Krüger, 1902 View in CoL :

Pornothemis serrata Krüger, 1902 View in CoL ;— Krüger, 1902: 163–164 (original description from North Sumatra);—Dow et al. 2024: 54 (summary of distribution), 79 (note 94—taxonomy).

Selected reference for Pornothemis sp. cf. serrata View in CoL :

Pornothemis serrata Krüger, 1902 View in CoL A;—Dow 2021: 378–379, Note 81 (summary of records from Sarawak, taxonomic note).

Specimens collected. M2a: 1 ♂ ( RER20 _ LIB86 About LIB ; RER), 16 i 2020; M4a : 5 ♂♂ ( RER23 _ LIB216–220 About LIB ; RER), 5 vi 2023; M4b : 4 ♂♂ ( RER23 _ LIB87–90 About LIB ; RER), 13 ii 2023 ; 1 ♂, 1 ♀ ( RER23 _ LIB221–222 About LIB ; RER), 5 vi 2023 ; 2 ♂♂ ( RER23 _ LIB225–226 About LIB ; RER), 13 vi 2023 ; 1 ♂, 1 ♀ ( RER23 _ LIB338–339 About LIB ; RER), 27 ix 2023; M5b : 1 ♂ ( RER23 _ LIB227 About LIB ; RER), 17 vi 2023; M5e : 1 ♀ ( RER23 _ LIB223 About LIB ; RER), 6 vi 2023; M5f : 1 ♂ ( RER23 _ LIB340 About LIB ; RER), 28 ix 2023; M10a : 1 ♂ ( RER23 _ LIB224 About LIB ; RER), 8 vi 2023; P1b : 1 ♂ ( RER23 _ LIB213 About LIB ; RER), 31 v 2023 ; 2 ♂♂ ( RER23 _ LIB214–215 About LIB ; RER), 2 vi 2023; P1c : 2 ♂♂ ( RER23 _ LIB336–337 About LIB ; RER), 24 ix 2023 .

Remarks. This is the taxon listed as P. serrata A in, for instance, Dow (2021). Until recently it was not possible to tell which of three similar taxa was the true P. serrata . At least in the lowlands this is a PSF species while the true P. serrata appears to be primarily a species of freshwater swamp forest. The first author is working on a revision of Pornothemis and it would be premature to make further comments here.

Pornothemis starrei Lieftinck, 1948

Selected references:

Pornothemis starrei Lieftinck, 1948 View in CoL ;— Lieftinck 1948a: 270 (original description from South Sumatra);—Dow et al. 2024: 54 (summary of distribution in Sundaland).

Specimens collected. M7h: 1 ♂ ( RER23 _ LIB228 About LIB ; RER), 15 vi 2023 .

Remarks. Recorded from Riau Province for the first time. One individual was collected and another seen in the same stand of freshwater mangrove beside the Kampar River where M. megabinluyog was found. Although described from South Sumatra the only later Sumatran records had been from Belitung ( Alfarisyi 2018, 2019). Although fairly widely distributed in Sundaland, this species has not often been recorded but might well be more common than is currently obvious. It appears to prefer mangrove and nipa palm habitats that are difficult to work in and is often found at the banks of rivers or around creeks with deep water in these habitats, so that a boat is required to find it.

Potamarcha Karsch, 1890

Potamarcha congener ( Rambur, 1842) View in CoL

Selected references:

Potamarcha congener ( Rambur, 1842) View in CoL ;— Karsch 1891: 245 (first record from Sumatra: North Sumatra);— Dow et al. 2018: 16 (first records from Riau).

Specimens collected. P4a: 1 ♂ ( RER23 _ LIB229 About LIB ; RER), 31 v 2023 ; 1 ♂ ( RER23 _ LIB230 About LIB ; BRIN), 31 v 2023 ; 1 ♂ ( RER23 _ LIB231 About LIB ; UMRI), 31 v 2023 ; P5a: 1 ♂ ( RER23 _ LIB342 About LIB ; UMRI), at the shallow pool beside the stream, 22 ix 2023 ; P5f: 1 ♂ ( RER23 _ LIB341 About LIB ; BRIN), 22 ix 2023 .

Remarks. Seemingly fairly common on the mineral soils at the base of the Kampar Peninsula but almost entirely absent from the peat soil part of the peninsula, where the only record is from a rain-fed artificial pond not in peat and presumably not with low pH water.

Rhodothemis Ris, 1909

Rhodothemis rufa ( Rambur, 1842) View in CoL

Selected references:

Rhodothemis rufa ( Rambur, 1842) View in CoL ;— Ris 1927: 43 (first record from Sumatra: West Sumatra);— Dow et al. 2018: 17 (first records from Riau).

Specimens collected. M1i: 1 ♂ ( RER20 _ LIB87 About LIB ; RER), 15 i 2020 ; 1 ♀ ( RER20 _ LIB88 About LIB ; BRIN), found in spider’s web, 18 i 2020 ; M1j: 1 ♂ ( RER23 _ LIB343 About LIB ; RER), 2 x 2023 ; M2e: 1 ♂ ( RER23 _ LIB91 About LIB ; BRIN), just before dusk, 6 ii 2023 ; 1 ♂ ( RER23 _ LIB233 About LIB ; BRIN), 10 vi 2023 ; 1 ♀ ( RER23 _ LIB234 About LIB ; UMRI), 10 vi 2023 ; M3c: 1 ♀ ( RER23 _ LIB92 About LIB ; UMRI), 10 ii 2023 , leg. RER staff; 1 ♀ ( RER23 _ LIB116 About LIB ; BRIN), 10 ii 2023 , leg. RER staff; M5a: 1 ♂ ( RER20 _ LIB89 About LIB ; UMRI), 20 i 2020 ; 1 ♂ ( RER20 _ LIB94 About LIB ; UMRI), 25 i 2020 ; M7a: 1 ♂ ( RER20 _ LIB91 About LIB ; BRIN), 23 i 2020 ; 1 ♀ ( RER20 _ LIB92 About LIB ; UMRI), perched in dry hole just inside acacia, 23 i 2020 ; 1 ♂ ( RER23 _ LIB93 About LIB ; UMRI), 19 ii 2023 ; 1 ♂ ( RER23 _ LIB94 About LIB ; BRIN), 19 ii 2023 ; M7c: 1 ♂ ( RER20 _ LIB93 About LIB ; BRIN), 23 i 2020 ; M9a: 1 ♂ ( RER20 _ LIB90 About LIB ; RER), 21 i 2020 ; M11a: 1 ♂ ( RER23 _ LIB235 About LIB ; BRIN), 11 vi 2023 ; P3a: 1 ♂ ( RER23 _ LIB232 About LIB ; UMRI), 30 v 2023 ; P5d: 1 ♀ ( RER23 _ LIB236 About LIB ; RER), 21 vi 2023 .

Remarks. Generally common at open waters in the Kampar Peninsula.

Rhyothemis Hagen, 1867

Rhyothemis aterrima Selys, 1891

Selected references:

Rhyothemis aterrima Selys, 1891 View in CoL ;— Krüger 1902: 91 (first record from Sumatra: North Sumatra);— Ris 1913: 953 (first record from Riau).

Specimens collected. M1a: 2 ♂♂ ( RER20 _ LIB96 About LIB , 99 About LIB ; BRIN), 19 i 2020 ; 1 ♂ ( RER20 _ LIB97 About LIB ; UMRI), 19 i 2020 ; 1 ♂ ( RER20 _ LIB98 About LIB ; RER), 19 i 2020 ; 1 ♂ ( RER23 _ LIB95 About LIB ; BRIN), semi-teneral, 12 ii 2023 ; M1c: 1 ♂ ( RER20 _ LIB95 About LIB ; RER), 15 i 2020 ; M1j: 1 ♂ ( RER23 _ LIB345 About LIB ; BRIN), 2 x 2023 ; 1 ♂ ( RER23 _ LIB346 About LIB ; UMRI), 2 x 2023 ; 1 ♂ ( RER23 _ LIB347 About LIB ; RER), 2 x 2023 ; M2e: 1 ♂ ( RER23 _ LIB238 About LIB ; UMRI), 10 vi 2023 ; M4d: 1 ♂ ( RER23 _ LIB344 About LIB ; UMRI), 27 ix 2023 ; M5a: 1 ♂ ( RER20 _ LIB100 About LIB ; UMRI), 20 i 2020 ; 1 ♂ ( RER20 _ LIB101 About LIB ; RER), 20 i 2020 ; 1 ♂ ( RER20 _ LIB102 About LIB ; BRIN), 20 i 2020 ; M7a: 1 ♂ ( RER20 _ LIB103 About LIB ; UMRI), 23 i 2020 ; 1 ♂ ( RER23 _ LIB96 About LIB ; UMRI), 19 ii 2023 ; M11a: 2 ♂♂ ( RER23 _ LIB239 About LIB , 241 About LIB ; BRIN), 11 vi 2023 ; 1 ♂ ( RER23 _ LIB240 About LIB ; UMRI), 11 vi 2023 ; P1c: 1 ♂ ( RER23 _ LIB237 About LIB ; BRIN), 2 vi 2023 .

Remarks. Rhyothemis aterrima thrives in low pH waters (although it is not confined to them) and this is very evident in the Kampar Peninsula where the species is common on open sections of PSF streams with emergent vegetation and even occurs on some sections of drain at the acacia edge.

Rhyothemis obsolescens Kirby, 1889

Selected references:

Rhyothemis curiosa Selys, 1889 ;—Selys 1889: 451 (first records from Sumatra: North Sumatra including Nias).

Rhyothemis obsolescens Kirby, 1889 View in CoL ;— Lieftinck, 1935a: 17 (first record from Riau).

Specimens collected. M1f: 1 ♂ ( RER20 _ LIB104 About LIB ; RER), 19 i 2020; M1h : 1 ♂ ( RER20 _ LIB105 About LIB ; BRIN), 19 i 2020; M1j : 1 ♂ ( RER23 _ LIB351 About LIB ; UMRI), 2 x 2023; M 1m : 1 ♂ ( RER23 _ LIB99 About LIB ; UMRI), 16 ii 2023; M4c : 1 ♂ ( RER23 _ LIB245 About LIB ; UMRI), 5 vi 2023; M4d : 1 ♂ ( RER23 _ LIB97 About LIB ; RER), 8 ii 2023; M5a : 2 ♂♂ ( RER20 _ LIB106– 107 About LIB ; UMRI), 20 i 2020 ; 2 ♂♂ ( RER20 _ LIB108–109 About LIB ; RER), 20 i 2020 ; 1 ♂, 1 ♀ ( RER20 _ LIB110–111 About LIB ; BRIN), 20 i 2020 ; 1 ♂ ( RER20 _ LIB112 About LIB ; UMRI), 25 i 2020 ; 1 ♂ ( RER23 _ LIB98 About LIB ; BRIN), 9 ii 2023; M5e : 1 ♂ ( RER23 _246; BRIN), 6 vi 2023; M12a : 1 ♀ ( RER23 _ LIB247 About LIB ; RER), 18 vi 2023 ; 1 ♂ ( RER23 _ LIB350 About LIB ; BRIN), 29 ix 2023; P1a : 1 ♂ ( RER23 _ LIB242 About LIB ; BRIN), 31 v 2023; P1c : 1 ♂ ( RER23 _ LIB243 About LIB ; UMRI), 2 vi 2023 ; 1 ♂ ( RER23 _ LIB244 About LIB ; BRIN), 2 vi 2023; P1e : 1 ♀ ( RER23 _ LIB349 About LIB ; UMRI), 24 ix 2023; P6c : 1 ♂ ( RER23 _ LIB348 About LIB ; RER), 23 ix 2023 .

Remarks. Rhyothemis obsolescens is common in swampy habitats, forest edge ponds and slow, open and semi-open streams in swamp; very common in such habitats in the main part of the Kampar Peninsula.

Rhyothemis phyllis phyllis (Sulzer, 1776)

Selected references:

Rhyothemis phyllis (Sulzer, 1776) View in CoL ;—Selys 1889: 450 (first record from Sumatra: South Sumatra);— Ris 1927: 44 (first record from Riau).

Specimens collected. M2e: 1 ♂ ( RER23 _ LIB249 About LIB ; UMRI), 10 vi 2023; M3a : 1 ♀ ( RER20 _ LIB113 About LIB ; RER), 17 i 2020 ; 1 ♀ ( RER23 _ LIB100 About LIB ; BRIN), 10 ii 2023, leg. RER staff; M7d : 1 ♂ ( RER23 _ LIB101 About LIB ; UMRI), 19 ii 2023; M 7g : 1 ♂ ( RER23 _ LIB102 About LIB ; RER), 19 ii 2023; P3a : 1 ♂ ( RER23 _ LIB248 About LIB ; BRIN), 30 v 2023; P5d : 1 ♂ ( RER23 _ LIB250 About LIB ; RER), 21 vi 2023; P6c : 1 ♀ ( RER23 _ LIB352 About LIB ; BRIN), 23 ix 2023 .

Remarks. Another species that is much more common in the Kampar Peninsula than the records above suggest, with individuals frequently seen flying at open drains in the acacia.

Risiophlebia Cowley, 1934

Risiophlebia dohrni ( Krüger, 1902) View in CoL

Selected references:

Nannophlebia dohrni Krüger, 1902 View in CoL ;— Krüger 1902: 186–187 (original description from North Sumatra).

Risiophlebia dohrni View in CoL ;— Lieftinck 1935a: 12 (first record from Riau).

Specimens collected. M5b: 1 ♂ ( RER23 _ LIB103 About LIB ; RER), 9 ii 2023 ; 1 ♀ ( RER23 _ LIB253 About LIB ; RER), 17 vi 2023; P1b : 1 ♂ ( RER23 _ LIB251 About LIB ; BRIN), 2 vi 2023 ; 1 ♂ ( RER23 _ LIB252 About LIB ; UMRI), 2 vi 2023 .

Remarks. Risiophlebia dohrni is most often found in swamp forest but is usually local in occurrence even in such habitat and this is the case in the Kampar Peninsula where it was found at only two sites so far.

Tetrathemis Brauer, 1868

Tetrathemis flavescens Kirby, 1889

Selected references:

Tetrathemis flavescens Kirby, 1889 View in CoL ;— Krüger 1902: 191 (first record from Sumatra: North Sumatra).

Specimens collected. M5b: 1 ♀ ( RER23 _ LIB254 About LIB ; RER), 17 vi 2023 .

Remarks. Recorded from Riau Province for the first time. The single female collected was placing eggs in a mass on hair-like aerial roots hanging from horizonal shoot ca 20cm above shaded water between a log and the densely vegetated margin of the pool. Ngiam et al. (2024) describe similar oviposition behavior of this species in Singapore.

Tholymis Hagen, 1867

Tholymis tillarga ( Fabricius, 1798) View in CoL

Selected references:

Tholymis tillarga ( Fabricius, 1798) View in CoL ;— Karsch 1891: 245 (first record from Sumatra: North Sumatra);— Ris 1927: 44 (first record from Riau).

Specimens collected. M2f: 1 ♀ ( RER23 _ LIB256 About LIB : BRIN), 6 vi 2023; M3d : 1 ♀ ( RER23 _ LIB115 About LIB ; BRIN), 17 i 2020; M8b : 1 ♀ ( RER20 _ LIB114 About LIB ; RER), 13 i 2020; P3a : 1 ♀ ( RER23 _ LIB255 About LIB ; UMRI), 30 v 2023 .

Remarks. Another species that is more common in the Kampar Peninsula than the number of specimens collected suggests, frequently seen in the late afternoon and at dusk around drains and flooded areas in clearings.

Tramea Hagen, 1861

Tramea transmarina euryale (Selys, 1878)

Selected references:

Tramea euryale (Selys, 1878) ;—Selys 1889: 450 (first record from Sumatra: West Sumatra).

Specimens collected. M3a: 1 ♀ ( RER20 _ LIB116 About LIB ; RER), 17 i 2020 ; M3e: 1 ♂ ( RER20 _ LIB118 About LIB ; UMRI), 24 i 2020 ; M 7g: 1 ♂ ( RER20 _ LIB117 About LIB ; BRIN), 23 i 2020 ; 1 ♂ ( RER23 _ LIB257 About LIB ; RER), 15 vi 2023 ; 1 ♂, 1 ♀ ( RER23 _ LIB258–259 About LIB ; BRIN), in tandem, 15 vi 2023 .

Remarks. Common at the rain-fed pond beside the Kampar River at location M7 and probably common at drains in the acacia as well, where Tramea were quite often seen but much less often captured. It cannot however simply be assumed that all red-marked Tramea seen in the Kampar Peninsula are T. transmarina euryale since other similar looking Tramea might occur there, in particular T. phaeoneura Lieftinck, 1953 , which has been recorded in Belitung and might well occur in mainland Sumatra and which is most often found at low pH waters in Borneo. Recorded from Riau Province for the first time.

Tyriobapta Kirby, 1889

Tyriobapta kuekenthali ( Karsch, 1900) View in CoL

Selected references:

Tyriobapta kuekenthali ( Karsch, 1900) View in CoL ;— Ris 1919: 1122 (first record from Sumatra: Riau).

Specimens collected. M 1m: 1 ♂ ( RER23 _ LIB356 About LIB ; RER), 1 x 2023; M1o: 1 ♂ ( RER23 _ LIB357 About LIB ; RER), 1 x 2023; M4a: 1 ♂ ( RER23 _ LIB109 About LIB ; UMRI), 13 ii 2023; 2 ♂♂ ( RER23 _ LIB262 About LIB , 264 About LIB ; BRIN), 5 vi 2023; 1 ♂ ( RER23 _

LIB263 About LIB ; UMRI), 5 vi 2023; 1 ♂ ( RER23 _ LIB354 About LIB ; BRIN), 27 ix 2023; 1 ♂ ( RER23 _ LIB355 About LIB ; UMRI), 27 ix 2023; M4b: 1 ♂ ( RER23 _ LIB104 About LIB ; RER), 8 ii 2023; 1 ♂ ( RER23 _ LIB267 About LIB ; UMRI), 13 vi 2023; M4e: 1 ♂ ( RER23 _ LIB353 About LIB ; UMRI), 27 ix 2023; M5b: 2 ♂♂ ( RER23 _ LIB105 About LIB , 108 About LIB ; BRIN), 9 ii 2023; 1 ♂ ( RER23 _ LIB106 About LIB ; UMRI), 9 ii 2023; 1 ♂ ( RER23 _ LIB107 About LIB ; RER), 9 ii 2023; 1 ♂ ( RER23 _ LIB268 About LIB ; BRIN), 17 vi 2023; M5f: 1 ♂ ( RER23 _ LIB265 About LIB ; UMRI), 6 vi 2023; M10a: 1 ♂ ( RER23 _ LIB266 About LIB ; BRIN), 8 vi 2023; P1b: 1 ♂ ( RER23 _ LIB260 About LIB ; BRIN), 31 v 2023; 1 ♂ ( RER23 _ LIB261 About LIB ; UMRI), 31 v 2023 .

Remarks. Not found during the unusually dry conditions of January 2020, but when surface water was present in the PSF during the surveys from February 2023 onwards, T. kuekenthali was generally common in the PSF of the Kampar Peninsula.

Urothemis Brauer, 1868

Urothemis signata insignata (Selys, 1872)

Selected references:

Libellula sanguinea Burmeister, 1839 View in CoL (nec Müller, 1764);—Selys 1889: 468 (first record from Sumatra: West Sumatra?). Urothemis signata insignata (Selys, 1872) View in CoL ;— Dow et al. 2018: 18 (first record from Riau).

Specimens collected. M1a: 1 ♂ ( RER20 _ LIB120 About LIB ; BRIN), 15 i 2020 ; 1 ♂ ( RER20 _ LIB123 About LIB ; BRIN), 19 i 2020 ; 1 ♀ ( RER20 _ LIB124 About LIB ; UMRI), 19 i 2020 ; M1c: 1 ♂ ( RER20 _ LIB119 About LIB ; RER), 15 i 2020 ; M1l: 1 ♂ ( RER23 _ LIB112 About LIB ; BRIN), 15 ii 2023 ; 1 ♂ ( RER23 _ LIB361 About LIB ; UMRI), 1 x 2023 ; M1p: 1 ♂ ( RER23 _ LIB111 About LIB ; UMRI), 12 ii 2023 ; M2e: 1 ♂ ( RER23 _ LIB209 About LIB ; BRIN), 10 vi 2023 ; M3a: 1 ♂ ( RER20 _ LIB121 About LIB ; UMRI), 17 i 2020 ; 1 ♀ ( RER20 _ LIB122 About LIB ; RER), 17 i 2020 ; M5a: 1 ♂ ( RER20 _ LIB125 About LIB ; BRIN), 20 i 2020 ; 1 ♂ ( RER20 _ LIB128 About LIB ; UMRI), 25 i 2020 ; 1 ♂ ( RER23 _ LIB110 About LIB ; BRIN), 9 ii 2023 ; M7a: 1 ♂ ( RER20 _ LIB126 About LIB ; UMRI), 23 i 2020 ; 1 ♂ ( RER23 _ LIB113 About LIB ; UMRI), 19 ii 2023 ; M7b: 1 ♀ ( RER20 _ LIB127 About LIB ; BRIN), immature, 23 i 2020 ; M 7g: 1 ♂ ( RER23 _ LIB271 About LIB ; BRIN), 15 vi 2023 ; M11a: 1 ♂ ( RER23 _ LIB270 About LIB ; UMRI), 11 vi 2023 ; M12a: 1 ♂ ( RER23 _ LIB360 About LIB ; BRIN), 29 ix 2023 ; M13a: 1 ♂ ( RER23 _ LIB272 About LIB ; RER), 18 vi 2023 ; P5d: 1 ♂ ( RER23 _ LIB358 About LIB ; RER), 22 ix 2023 ; P6b: 1 ♂ ( RER23 _ LIB359 About LIB ; RER), 23 ix 2023 .

Remarks. The first record of this species from Sumatra was from “Soeroegoen [Surugun]”, collected by J.F. Snelleman (Selys 1889) during an expedition to central Sumatra that passed through several of the present day provinces, it is not clear where exactly this location was, but where the locations for other odonate material from the same source can be traced, they are all in present day West Sumatra, so “Soeroegoen” might well be in that province.

Zyxomma Rambur, 1842

Zyxomma petiolatum Rambur, 1842 View in CoL

Selected references:

Zyxomma petiolatum Rambur, 1842 View in CoL ;— Ris 1927: 43 (first records from Sumatra: Riau and West Sumatra).

Specimens collected. M2f: 1 ♂ ( RER23 _ LIB114 About LIB ; UMRI), 18 ii 2023 ; 1 ♂ ( RER23 _ LIB277 About LIB ; UMRI), at lights at ca. 7 PM, 4 vi 2023, leg. Eco Camp canteen staff; M3b: 1 ♂ ( RER20 _ LIB129 About LIB ; RER), 17 i 2020 ; M3d: 1 ♂ ( RER20 _ LIB130 About LIB ; BRIN), 17 i 2020 ; M7f: 1 ♀ ( RER23 _ LIB115 About LIB ; RER), 19 ii 2023 ; P2a: 1 ♂ ( RER23 _ LIB273 About LIB ; BRIN), 30 v 2023 ; 1 ♂ ( RER23 _ LIB274 About LIB ; UMRI), 30 v 2023 ; P4a: 1 ♀ ( RER23 _ LIB275 About LIB ; RER), found dead in spider web, 31 v 2023 ; 1 ♀ ( RER23 _ LIB276 About LIB ; BRIN), 2 vi 2023 .

Remarks. At least moderately common in the Kampar Peninsula and probably under-recorded because of its mostly crepuscular habits.