Taxonomic revision of Australian Copelatus Erichson, 1832 (Coleoptera, Dytiscidae, Copelatinae)

Abstract The genus Copelatus in Australia is revised and nine species are recognised. One new species, Copelatus martinbaehrisp. nov., is described from Papua New Guinea (Central Province) and Cape York Peninsula (Iron Range NP and Mt Tozer). Copelatus divisus Watts, 1978, syn. nov., is considered a junior synonym of C. portior Guignot, 1956, described from New Guinea. Species delimitation is based on the morphological characters and Cox1 data. All species are (re)described, and their important species characters (median lobes, parameres, habitus and colour patterns) are illustrated. A key to all nine species is provided. The known distribution and habitat preferences of each species are outlined briefly. In Australia, all nine species are distributed in the northern half of the continent. Four species are also reported from New Guinea: in addition to C. martinbaehrisp. nov., we record C. clarki Sharp, 1882 for the first time from southern New Guinea, and consider literature records of C. irregularis W.J. Macleay, 1871 and C. marginatus Sharp, 1882 from New Guinea as doubtful. Copelatus portior is widely distributed in Australasia, while C. tenebrosus is widely distributed in the Indomalayan and Australasian realms. All Australian Copelatus are confirmed to be lentic, found in a large variety of stagnant water, mainly in lowland areas up to 250 m.


Introduction
The genus Copelatus Erichson, 1832 has a worldwide distribution, with highest diversity in the tropics (Nilsson and Hájek 2019). With more than 400 described species, it We delineate the species using traditionally employed morphological characters such as shape, structure and setation of the male genitalia; size, shape and colour pattern of the body, shape of the male protibia, as well as features of the dorsal surface sculpture.

DNA sequencing and data analysis
The sequence data partly originate from Hendrich et al. (2010). We preserved a part of our collections in 96% ethanol and later extracted DNA for sequencing. The laboratory methods employed are detailed on our DNA laboratory wiki: https://zsm-entomology.de/wiki/The_Beetle_D_N_A_Lab. PCR conditions with Mango Taq (Bioline) were 1'94 °C -35× (30 s 94 °C -30 s 47 °C -1'72 °C) -10'72 °C -(hold at 14 °C) with primers Jerry and Pat to amplify and sequence the 3' of the gene encoding for cytochrome c oxidase 1 (Simon et al. 1994). All 46 individual vouchers bear a green cardboard label that indicates the DNA extraction number of M. Balke (e.g. "DNA M. Balke 2291"). This number links the DNA sample, the dried mounted voucher specimen, deposited in ZSM. We used a simple approach to calculate a neighbour joining tree (p-distances) in Geneious (11.0.4.) software (Fig. 29) and visual inspection to learn if there was any hidden diversity or haplotype sharing. The sequence data have been deposited at DRYAD (datadryad.org) as a Geneious project and in FASTA file format: https://datadryad.org/stash/dataset/doi:10.5061/dryad.w0vt4b8m7.

Taxonomy
The morphologically delineated species were all retrieved as monophyletic groups in our cox1 DNA sequence tree (Fig. 29). We observe geographic structure for the Western Australian and Queensland individuals of C. irregularis, but these are samples from most distant localities only, and the divergence amounts to only c. 1%.
Description of male. Body shape. In dorsal view, oblong oval, broadest at midlength of elytra, moderately convex. Body outline continuous, without discontinuity between pronotum and elytra. Head relatively broad; anterior margin of clypeus not bordered.
Pronotum broadest between posterior angles, lateral margins moderately curved. Base of elytra as broad as pronotal base; lateral margins of elytra moderately curved (Fig. 1).
Dorsal surface sculpture: Whole surface shiny (Fig. 1). Head uniformly microreticulated, reticulation composed of moderately deeply impressed isodiametric meshes. Punctation composed of very small punctures, sparsely spread on surface; rows of deep and coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with some moderately strong, short striae, more dense and weak laterally; lateral beading of pronotum very thin and indistinct. Microreticulation and punctation similar to that of head; row of coarse setigerous punctures present along anterior margin, basal margin (except for basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Punctation consisting of very fine sparse punctures. Each elytron with 11 strongly impressed discal and one submarginal longitudinal striae, intervals subequal, alternate striae tending to be shorter apically; subbasal stria reaching from middle of elytron almost to end of stria 10.
Antennae and legs: Antenna with antennomeres long and slender. Protibia straight, not modified. Pro-and mesotarsomeres 1-3 distinctly broadened, with adhesive discs on their ventral side; claws simple.
Male genitalia: Median lobe consisting of a few sclerites, closely attached together; apex in lateral view thin and elongate (Fig. 11A, B). Shape of paramere narrowly triangular, with thin, elongate subdistal part and weak but evident long setae along dorsal margin (Fig. 11D).
Female. Similar to male in habitus. Pro-and mesotarsomeres not broadened, without adhesive setae. Pronotal striae finer and denser.
Measurements. TL = 5.1-5.25 mm; TL-H = 4.5-4.65 mm; MW = 2.45-2.50 mm. Variability. All specimens studied are rather uniform in shape and colour, and vary only little in body length. Differential diagnosis. Copelatus bakewelli is close to the form of C. daemeli with 11 elytral striae and C. irregularis but smaller and without testaceous basal and apical markings on the elytra. Pronotal striae are weak (absent in C. daemeli) and the male protibia is not bent as in C. irregularis. Furthermore, all three species can easily be separated by the form of their median lobes.
Distribution. Endemic. The species occurs from the Kimberley region in northwestern Australia and in the Arnhemland in the Northern Territory to northern Queensland. In that area, the species is mainly distributed in rainforest pockets of the stone country (Fig. 20).

Copelatus clarki
Dorsal surface sculpture: Whole surface shiny (Fig. 2). Head uniformly microreticulated, reticulation weakly impressed with very small meshes. Densely, weakly and minutely punctate; rows of coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with lateral beading very thin and indistinct. Microreticulation and punctation similar to that of head; row of coarse punctures present along anterior margin, basal margin (except basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Punctation consisting of very fine sparse punctures. Apex of elytra with some large punctures. Each elytron with eight impressed discal and one submarginal longitudinal striae; stria 2 weakly impressed, reduced to a few elongated short striae; stria 1 well separated from suture and in position of innermost row of serial punctures, striae 4 and 6 shorter than striae 5, 7, and 8.
Antennae and legs: Antenna with antennomeres long and slender. Protibia modified, angled near base, slightly broadened anteriorly. Pro-and mesotarsomeres 1-3 distinctly broadened, with adhesive discs on their ventral side; claws simple.
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae.
Measurements. TL = 7.2-8.0 mm; TL-H = 6.5-7.15 mm; MW = 3.4-3.5 mm. Variability. All specimens studied are rather uniform but can vary in body length. In approximately half of the studied specimens, stria 2 on elytra is not interrupted and reduced to a few elongated short striae. There is a slight variation in the extension of the ferruginous basal band on elytra.
Differential diagnosis. The species can be separated from all other Australian Copelatus with more than six striae on elytron by the broad distance between the elytral suture and stria 1 (Watts 1978) and the shape of the median lobe. Copelatus clarki is the largest species of the genus in Australia.
Distribution. The species is widely distributed in the northern half of Australia. Records are from north-western Australia (Kimberley region), Northern Territories and Queensland south to Brisbane and Stradbroke Island (Fig. 22).
In this study, the species is recorded for the first time from southern New Guinea (Indonesia: Papua Province, Merauke Regency and Papua New Guinea: Western Province).

Habitat.
A widely distributed species in tropical northern Australia, C. clarki can be found in almost all lentic habitat types, in open country as well as forested areas (Larson 1993). Most specimens were obtained from isolated pools of seasonal creeks and streams, and pools adjacent to streams in Eucalypt or tropical woodland, filled from leaf and debris (Fig. 31A). During dry periods, the species occurred in high densities in shallow water under dense emergent grasses adjacent to the water's edge in irrigation reservoirs and dugouts (Larson 1993). On Stradbroke Island, the species was collected in the shallow water of a seasonal Baumea sedge swamp (Fig. 31B). The species is also attracted to light. Type locality. "Australia [Queensland] (Cape York)". Type material. We were not able to find the type material of C. daemeli, neither in Muséum national d'Histoire naturelle, Paris (MNHN) nor in the NHMUK. Copelatus daemeli is originally a manuscript name of Wehncke. The depository of many of Wehncke's types is unknown, but those which were found and studied are mostly stored in the MNHN. The identity of the species is quite clear and it cannot be confused with any other Australian (or New Guinean) species, therefore the designation of a neotype is not necessary and simply refers to undoubted identity of the species in the revision of Watts (1978).
Description of male. Body shape: In dorsal view, narrowly elongate, broadest at midlength of elytra. Body outline with small discontinuity between pronotum and elytra. Head relatively broad; anterior margin of clypeus not bordered. Pronotum broadest in middle, lateral margins moderately curved. Base of elytra as broad as pronotal base; lateral margins of elytra moderately curved (Fig. 4).
Dorsal surface sculpture: Whole surface shiny (Fig. 4). Head uniformly microreticulated, reticulation weakly impressed with very small meshes. Densely, weakly and minutely punctate; rows of coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with lateral beading very thin and indistinct. Microreticulation similar to that of head. Punctation similar to that of head; row of coarse punctures present along anterior margin, basal margin (except for basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Serial punctures very indistinct, located in striae 4, 6, 8 and 10. Each elytron with ten discal and one well marked submarginal longitudinal stria, alternate striae shorter apically and with a tendency to be interrupted basally. Striae 3 and 5 reduced to a few short grooves and stria 2 broken up basally. Submarginal stria reaching from middle of elytra almost to apical end of stria 10.
Antennae and legs: Antenna with antennomeres long and slender. Protibia modified, angled near base, slightly broadened anteriorly. Pro-and mesotarsomeres 1-3 distinctly broadened, with adhesive discs on their ventral side; claws simple.
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae.
Measurements. TL = 6.2-6.3 mm; TL-H = 5.5-5.6 mm; MW = 2.9-2.95 mm. Variability. A dimorphic species. Despite the fact that all specimens studied are rather uniform in habitus and colouration, they vary in extension and number of their elytral striae. Several specimens of both sexes, collected at the same spot at the same time with the main form (NT, Robin Falls), have 11 fully developed elytral striae. (Fig. 3).
Differential diagnosis. On the first view C. daemeli (especially the form with 11 elytral striae) resembles C. bakewelli but differs in the lack of short striae on the pronotum, the larger size, and the less developed and often shortened and reduced elytral striae in most of the specimens. Furthermore, both species can easily be separated by the form of the median lobe.
Distribution. Endemic. The species is distributed from the Kimberley region in Western Australia, over Northern Territory (Melville Island, Kakadu Area and around Darwin) to coastal Queensland (Cape York Peninsula) south to Townsville (Fig. 21). Always rare and collected only in low numbers.
Dorsal surface sculpture: Whole surface shiny (Fig. 5). Head uniformly microreticulated, reticulation composed of moderately deeply impressed isodiametric very small meshes. Punctation composed of very small punctures sparsely spread on surface; rows of deep and coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with some moderately strong, short striae, more dense and weak laterally; lateral beading of pronotum very thin and indistinct. Microreticulation and punctation similar to that of head; row of coarse setigerous punctures present along anterior margin, basal margin (except basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Punctation consisting of very fine sparse punctures. Each elytron with 11 strongly impressed discal and one submarginal longitudinal striae, intervals subequal, alternate striae tending to be shorter apically; submarginal stria reaching from little behind middle of elytron almost to end of stria 10. Serial punctures on elytron untraceable.
Female. Similar to male in habitus. Pro-and mesotarsomeres not broadened, without adhesive setae. Pronotal striae fine and dense.
Measurements. TL = 6.8-7.8 mm; TL-H = 6.0-6.9 mm; MW = 3.2-3.4 mm. Variability. All specimens studied are rather uniform in shape and size but vary in the extension of the testaceous elytral markings. Differential diagnosis. The species is close to C. bakewelli but can be easily separated by the larger size, the dorsal colouration, and the form of the median lobe.
Distribution. The species is widely distributed in the northern half of Australia. Records are from the Northern Territory (inland to the East MacDonnell Ranges), north-western Australia (Kimberley region and the Pilbara), and Queensland south to Brisbane (Fig. 23).
Habitat. This is a widely distributed species and one of the most common Copelatus in tropical northern Australia. It can be found in almost all habitat types, preferably in forested areas. Most specimens were obtained from shallow water, amongst leaves and plant debris, of isolated pools of seasonal creeks and streams, and pools adjacent to streams in Eucalypt or tropical woodland. Also, a few specimens were taken from slow flowing spring-fed streams. In the Pilbara (Hendrich 2002), C. irregularis was found in different isolated and half-shaded rocky and sandy pools (10-20 m², up to 1.5 m depth) of an intermittent stream. The bottom of most habitats consisted of sand and stones, with a thin layer of mud and plant debris (Figs 31A, 34A). Copelatus irregularis is also attracted to light.

Description of male. Body shape:
In dorsal view oval, almost ovoid, broadest in basal third of elytra, moderately convex. Body outline without discontinuity between pronotum and elytra. Head relatively broad; anterior margin of clypeus truncate. Pronotum broadest between posterior angles, lateral margins moderately curved. Base of elytra as broad as pronotal base; lateral margins of elytra moderately curved (Fig. 6).
Dorsal surface sculpture: Whole surface almost matt (Fig. 6). Head uniformly microreticulated, reticulation composed of moderately deeply impressed meshes. Punctation composed of coarse setigerous punctures, and very small punctures spreading sparsely on surface; rows of coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with lateral beading very thin and indistinct. Microreticulation and punctation similar to that of head; row of coarse setigerous punctures present along anterior margin, basal margin (except for basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Serial punctures on elytra rather weak. On each elytron six moderately impressed thin discal and one submarginal longitudinal striae, progressively closer towards sides; stria 1 (sutural stria) reduced to apical fourth, striae 2 and 4 complete, striae 3 and 5 a little shorter basally. Submarginal stria short, expanding from behind middle of elytron to end of stria 6.
Antennae and legs: Antenna with antennomeres long and slender. Protibia modified, distinctly broadened anteriorly. Pro-and mesotarsomeres 1-3 distinctly broadened, with adhesive discs on their ventral side; claws simple.
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae. Pronotum basolaterally with numerous short longitudinal strioles. Elytra between striae and side with numerous short longitudinal strioles.
Variability. All specimens studied are rather uniform and vary only in body length. In some specimens, the submarginal stria is reduced to few elongate grooves.
Differential diagnosis. The species is close to C. tenebrosus but can be easily separated by the larger size, much shorter inner striae of elytra, and the form of the median lobe.
Distribution. The species occurs in tropical and subtropical northern and central Australia, along the east coast south to Brisbane (WA, NT, QLD) (Fig. 25). Addi-tionally, C. marginatus was recorded from New Caledonia (South Province) and West Samoa by Wewalka et al. (2010). Zimmermann (1927: 17) reported the species from Tonga (two specimens from Tonga: Nukualofa, 22.xi.1925). He wrote also that the presence of the species in Samoa is confirmed by material of Dr K. Friederichs (Friederichs 1922: 148: Samoa, five specimens). Later, C. marginatus was reported from Samoa (Upolu), Fiji (Viti Levu and Vanua Levu) and New Guinea (Dorey, now Manokwari, Indonesia: West Papua Province) by Balfour-Browne (1945: 106 and 113) which was repeated by some later authors (Guéorguiev 1968: 21;Guéorguiev and Rocchi 1993: 159;Wewalka et al. 2010: 51). The records from Fiji and New Guinea are in need of confirmation.
Habitat. Most specimens were collected during or just after the rainy season when the beetles can be collected in seasonal flood meadows along rivers and creeks, shallow roadside ditches and swampy areas. At that time of the year, C. marginatus is often attracted in larger numbers to light (e.g., Normanton). In north-eastern Queensland, the species was collected in a small roadside pool and in isolated pools in seasonal fingertip tributary streams, all in closed forest (Larson 1993).  Description of male holotype. Body shape: In dorsal view, oblong-oval, broadest in basal third of elytra, moderately convex. Body outline without discontinuity between pronotum and elytra. Head relatively broad; anterior margin of clypeus not bordered. Pronotum broadest between posterior angles, lateral margins moderately curved. Base of elytra as broad as pronotal base; lateral margins of elytra moderately curved (Fig. 7).

Copelatus martinbaehri
Colouration: Body black, most of clypeus, anterior angles of pronotum, base and tip of elytra, appendages and much of ventral surface testaceous.
Dorsal surface sculpture: Whole surface shiny (Fig. 7). Head uniformly microreticulated, reticulation composed of moderately deeply impressed isodiametric very small meshes. Punctation composed of very small punctures spread sparsely on surface; rows of deep and coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with some weak and short striae laterally. Microreticulation and punctation similar to that of head; row of coarse setigerous punctures present along anterior margin, basal margin (except for basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. Punctation consisting of very fine sparse punctures. Each elytron with six strongly impressed discal and one submarginal longitudinal striae, intervals subequal, striae 1 and 5 tending to be shorter basally; submarginal stria reaching from little behind midlength of elytron almost to end of stria 6. Serial punctures on elytron untraceable.
Ventral part: Finely microreticulated, with intermixed, sparsely distributed, very small punctures. Prosternal process rather flat, distinctly bordered laterally, weakly and bluntly pointed. Lateral parts of metaventrite tongue-shaped, very slender. Metacoxal lines close, well-marked and moderately divergent anteriorly. Metacoxae with long and deep striae, abdominal ventrite I with numerous striae and ventrites 2-3 with a few longitudinal striae.
Female. Similar to male in habitus. Protibia not modified. Pro-and mesotarsomeres not broadened, without adhesive setae.
Variability. All specimens studied are rather uniform in shape and size but vary a bit in the extension of the testaceous elytral markings.
Differential diagnosis. Based on the characteristic sickle-shaped median lobe, the new species belongs to a difficult complex of species distributed in the Sunda Islands and New Guinea, including C. geniculatus Sharp, 1882, C. gentilis Sharp, 1882, C. lineatus (Guérin-Méneville, 1838 and C. subterraneus Guéorguiev, 1978 (of the C. irinus species group) and several additional undescribed species, both from the C. irinus group (i.e., with six dorsal striae on elytra) and the C. trilobatus group (with 11 dorsal striae). All those species are rather uniform in body shape and colouration; they differ in elytral striation (which may be, however, variable) and less so in the shape of the median lobe in lateral view, especially in the width of the medial part and in length and curvature of the apical part. Copelatus martinbaehri sp. nov. differs from the other species of this complex by the shape of the median lobe, which has the central part in lateral view broader, but without distinct tubercle on the ventral side; additionally, the apical part is shorter and almost straight (the angle between central and apical part of median lobe in lateral view is nearly rectangular).
Within other Australian species with six elytral striae, Copelatus martinbaehri sp. nov. can be easily distinguished by its larger size (C. tenebrosus is always less than 5 mm), more elongate habitus (C. portior more ovoid, oval), elytral colouration (C. marginatus and C. tenebrosus with almost black dorsal surface), and the shape of the median lobe.
Etymology. This species is dedicated in honour of our late colleague Dr Martin Baehr (*10.3.1943, †17.4.2019, coleopterist, arachnologist, and others as well as the most knowledgeable authority for Australian ground beetles. The specific epithet is a substantive in the genitive case. Distribution. Northern Queensland (Iron Range National Park at Cape York Peninsula) and south-eastern Papua New Guinea (Central Province) (Fig. 28).
Habitat. Unknown. Most probably, the new species is an inhabitant of temporary lowland rainforest pools. The type specimens were collected in a Malaise Trap and at light. Description of male. Body shape: In dorsal view, elongate oval, broadest at midlength of elytra, moderately convex. Body outline without discontinuity between pronotum and elytra. Head relatively broad, anterior margin of clypeus truncate. Pronotum broadest between posterior angles, lateral margins moderately curved. Base of elytra as broad as pronotal base; lateral margins of elytra moderately curved (Fig. 8).
Dorsal surface sculpture: Whole surface shiny (Fig. 8). Head uniformly microreticulated, reticulation composed of moderately deeply impressed isodiametric meshes. Punctation composed of small punctures, smaller than meshes of reticulation; rows of coarse punctures present around inner margin of eyes and in small depression anterolaterally of eyes. Pronotum with lateral beading very thin and indistinct. Microreticulation and punctation similar to that of head; row of coarse setigerous punctures present along anterior margin, basal margin (except for basomedially), and laterally close to sides. Elytra with microreticulation similar to that of head and pronotum, but less impressed. On each elytron 11 sharply incised discal striae present, inner three striae only weakly impressed anteriorly.
Antennae and legs: Antenna with antennomeres long and slender. Protibia modified, slightly broadened anteriorly. Protarsomeres 1-3 distinctly broadened and mesotarsomeres less so, with adhesive discs on their ventral side; claws simple.
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae.
Measurements. TL = 5.5-5.8 mm; TL-H = 4.9-5.2 mm; MW = 2.5-2.6 mm. Variability. All specimens studied are rather uniform and vary only in body length. Differential diagnosis. Copelatus nigrolineatus is distinguished from all other Australian species by the absence of submarginal striae on the elytra, the pale dorsal surface and the form of the median lobe.
Distribution. Endemic. The species is widely distributed in the northern half of Australia. Numerous records are from the Northern Territory, north-western Australia (Kimberley region and the Pilbara), and Queensland south to Brisbane (Fig. 26). The single records from South Australia ("Elliston", SAMA) and New South Wales ("Wakool", AMS) are in need of confirmation. Most probably those single specimens were drifted southwards by heavy thunderstorms, followed by flash floods.
Habitat. This widely distributed species is the most common Copelatus in the Northern Territory and north-western Australia and was found in almost all habitat types. It occurs in both open country as well as forested areas. Most specimens were obtained from isolated flood-zone pools of seasonal rivers and pools adjacent to streams in Eucalypt or tropical woodland. The species tended to be found more in seepage areas or on mineral substrates than other the Australian Copelatus (Larson 1993). Also, a few specimens were taken from slow flowing spring-fed streams (Figs 34B, 35A, B). Copelatus nigrolineatus is also attracted to light.
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae.
Measurements. TL = 5.0-5.7 mm; TL-H = 4.7-5.3 mm; MW = 2.7-2.85 mm. Variability. All specimens studied are rather uniform and vary only in body length and dorsal colouration. In some specimens, sides of elytron and areas between striae often lighter. A single female from Holmes Jungle Park in Darwin is on dorsal surface almost black, matt and with coarse microreticulation and numerous strioles on elytra and pronotum.
Differential diagnosis. Copelatus portior can be separated from the similar C. tenebrosus and C. martinbaehri sp. nov. by its broad and ovoid body shape, colouration of pronotum and elytra, and the six well-developed and strong elytral striae. Furthermore, it is the only Australian species with an anchor-like median lobe.
Comments on classification. Copelatus portior is closely related to the widespread Oriental species Copelatus oblitus Sharp, 1882 with which it shares a characteristic shape of male genitalia with anchor-like, medially bifid median lobe. We compared the holotypes of both C. portior and C. divisus and have found no differences between these two taxa. Therefore, we consider Copelatus divisus Watts, 1978 a junior subjective synonym of Copelatus portior Guignot, 1956. Distribution. The species occurs in the coastal tropical rainforest areas of the Northern Territory and north-eastern Queensland, from northern Peninsula (Lockerbie) to Mackay in the south (Fig. 24). Additionally, C. portior is known from northern part of Papua New Guinea: Sandaun Province, Seleo Island, and Madang Province, Friedrich-Wilhelmshafen, now Madang, (Guignot 1956: 53, localities for holo-and allotypes).
Habitat. Copelatus portior was mainly collected in puddles and pools in temporary flooded swamp forests (Fig. 33A, B), low gradient streams and drainage ditches at the edge of cane fields (Larson 1993), and in residual pools of shallow, intermittent and smaller creeks. The beetles hide among fallen leave litter and dense emergent grasses. The substrate was generally clay. Larson (1993) collected most of his specimens in open sites where rainforest had been cleared. Copelatus portior is commonly attracted at light. The species is regularly collected but never abundant or in larger numbers. Type locality. "[Indonesia, Sumatra] Solok, District of Rawas, Soeroelangoen". Type material. Not studied. The type specimens should be deposited in the Naturalis Biodiversity Center, Leiden, The Netherlands (former Rijksmuseum van Natuurlijke Historie), but they were not found during a visit of JH. The designation of the lectotype by Watts (1978: 124) based on specimens from "Siam, Bangkok" and deposited in NHMUK is invalid and concerns almost surely the type material of Copelatus pusillus Sharp, 1882 (a junior subjective synonym of C. tenebrosus); Copelatus tenebrosus was described based on specimens from Sumatra.

Copelatus tenebrosus
Additional material studied ( Male genitalia: Median lobe apically more or less evenly narrow in ventral view, and very strongly curved downwards in lateral view (Fig. 19A, B, C). Shape of paramere broad triangular, with weak, short setae along dorsal margin of subdistal part (Fig. 19D).
Female. Similar to male in habitus. Protibia simple, not angled basally and only slightly broadened distally; pro-and mesotarsomeres not broadened, without adhesive setae.
Differential diagnosis. The species is similar to C. marginatus but can be easily separated by the smaller size (smallest species of the genus in Australia), fully developed inner striae of elytra, and the shape of the median lobe.
Distribution. This is the most widespread species in the Indomalayan and Australasian realms. It occurs from Nepal, India, and Sri Lanka over Myanmar, Laos, Vietnam, Thailand, Philippines, Indonesia (Hendrich and Balke 1995), Malaysia, and New Guinea (Hendrich et al. 2004) to coastal northern and eastern Australia, south to Townsville (Fig. 27).
Habitat. The wide distribution of this species owes to the ability of adaptation to manmade habitats like rice or paddy fields and shallow irrigation ditches (Hendrich et al. 2004). In Australia, C. tenebrosus inhabits open, treeless and seasonally flooded meadows, billabongs, ponds, paddy fields (Larson 1993), puddles, swamps and roadside ditches with dense vegetation, often with mats of floating grasses (Figs 33A, B,  36A, B). The species is not that common in Australia as it is in many other countries of Southeast Asia (Hendrich and Balke 1995;Hendrich et al. 2004), and its population density in one spot is always very low.