Introduction of the Exocelinacasuarina-group, with a key to its representatives and descriptions of 19 new species from New Guinea (Coleoptera, Dytiscidae, Copelatinae)

Abstract Nineteen new species of Exocelina Broun, 1886 from New Guinea are described herein: E.adelbertensissp. n., E.ambuasp. n., E.bewanisp. n., E.cyclopssp. n., E.ibalimisp. n., E.kekisp. n., E.kumulensissp. n., E.mendiensissp. n., E.menyamyasp. n., E.okapasp. n., E.piusisp. n., E.pseudofumesp. n., E.pseudopusillasp. n., E.pusillasp. n., E.simasp. n., E.simbaiensissp. n., E.simbaijimisp. n., E.sumokedisp. n., and E.yoginofisp. n. All of them, together with five already described species, have been united into the newly defined casuarina-group, a polyphyletic complex of related species with similar shape of the median lobe and paramere setation. An identification key to all known species of the group is provided, and important diagnostic characters (habitus, color, male protarsomeres 4–5, median lobes, and parameres) are illustrated. Data on the distribution of the species are given, showing that most of the species occur in the central, mountain part of Papua New Guinea.


Introduction
Herein, we introduce the new species group of the genus Exocelina Broun, 1886. After the ekari-group with 51 species, it is the second largest species group of the New Guinea Exocelina (Balke et al. 2007, Shaverdo et al. 2012, 2016a. The group includes 24 species: 19 new species, which are described and illustrated here, and five previously known species: E. casuarina , E. fume , E. desii (Balke, 1999), E. heidiae , and E. messeri (Balke, 1999). Based on the results of a molecular phylogenetic analysis and morphological study, these species are suggested to be closely related and form a monophyletic complex including two monotypic groups (undescribed species) and the okbapensis-and aipo-groups (Fig. 1;Balke et al. 2007;Shaverdo et al. 2017;Toussaint et al. 2014Toussaint et al. , 2015. Also, they build the core of a larger monophyletic complex (including the ullrichi-group), which is a sister clade to all other New Guinea Exocelina (Toussaint et al. 2015). Morphologically, species of the casuarina-group are identified by a complex of characters, among which the important ones are shape of the paramere and median lobe and setation of the paramere.
Including the results of this work, 125 species of Exocelina are described from New Guinea and 180 species worldwide.
As in most of our previous papers on the genus (Shaverdo et al. 2012(Shaverdo et al. , 2013(Shaverdo et al. , 2016a(Shaverdo et al. , b, c, 2017, all species data will be presented on the species-id.net portal automatically created by ZooKeys with the publication of this paper. (total body length), TL-H (total body length without head), MW (maximum body width), and hw (handwritten). Figure 1 shows phylogenetic relationships of species within the Exocelina casuarina-group based on the MrBayes phylogenetic tree in figure S1 of Toussaint et al. (2015) and includes results of most recent phylogenetic investigations (Shaverdo and Balke in preparation).
-habitus elongate to oval, in most species oblong-oval (broadest approximately at elytral midlength); with rounded pronotal and elytral sides, body outline continuous; -pronotum short, trapezoidal, with posterior angles not drawn backwards; -coloration reddish to piceous, mainly uniform, sometimes with paler head and pronotum and darker elytra; -microreticulation and punctation of dorsal surface very fine to strongly impressed, beetles shiny to matt dorsally; -metacoxae and abdominal ventrites 1-5 (and 6 in males) with thin, almost longitudinal striae/strioles; -pronotum and elytra without striae or strioles; -pronotum with or without lateral bead; -antennomeres not modified; -male protarsomeres 1-3 not expanded laterally; -male protarsomere 4 cylindrical, narrow, with anterior angle slightly expanded in some species, with a large, hook-like to thin, long, slightly curved anterolateral seta; -male protarsomere 5 long and narrow, sometimes slightly concave ventrally; -median lobe of aedeagus with continuous outline in ventral and lateral view; almost straight or slightly curved in lateral view; in ventral view, almost parallel-sided, often narrowed distally before apex or towards it, or broadened subdistally; apex usually with thickened sides, slightly or distinctly enlarged ("swollen", often ventrally of shape of a baby pacifier), rounded, truncate, or slightly concave in ventral view; -ventral sclerite of median lobe more or less deeply divided apically; -median lobe without setation, in some species with minuscule spines; -paramere without dorsal notch and with long, dense, thin setae, situated along dorsal margin, subdistal setae usually denser and stronger than proximal ones.
Although the species of the group do not form a monophyletic complex with the distinguished autapomorphic morphological character ( Fig. 1; Toussaint et al. 2014Toussaint et al. , 2015, we designate this species group since its representatives are assumed to be closely related and for ease of their identification. The group can be clearly differentiated (keyed out) using the characters proposed above (also in Shaverdo and Balke in preparation). Additionally, most of its species are readily distinguished by the thickened apex of their median lobe in lateral view, which is a character in common for all the members of this group. Surprisingly, in ventral view, this "swollen" apex can be very differently formed, from broadly pointed to truncate or slightly concave. In addition, the shape (absence of dorsal notch) and setation (subdistal setae denser than proximal ones) of the paramere is useful for species differentiation of this group, especially the few species that do not have this characteristic "swollen" apex or where it is not strongly enough expressed, from some species of the okbapensis-and ransikiensis-groups.
Phylogenetically, the group is polyphyletic and includes five different clades, which are partially supported morphologically and contribute to two larger monophyletic complexes: 1) clades I and II plus the okbapensis-group and 2) clades III, IV, and V plus two monotypic groups (two undescribed species, which are very different morphologically from all the other species of the clades) ( Fig. 1; Toussaint et al. 2015).
Clade I includes E. simbaiensis sp. n., E. yoginofi sp. n. and, probably, E. okapa sp. n. (based on morphology). These species build a monophyletic complex with the species of the okbapensis-and aipo-groups. Interestingly, the two latter species demonstrate a distinct similarity with the species of the okbapensis-group in the shape of the median lobe and setation of paramere, though E. simbaiensis sp. n. does not.
Clade II is morphologically rather heterogeneous and is comprised of the largest (size) representatives of the group. Three of them, E. desii, E. simbaijimi sp. n. and, probably, E. heidiae (based on morphology), form a monophyletic complex and have broad, similar in shape median lobes. The remainder have median lobes distinctly narrower and more different in shape.
Clade III includes species without lateral pronotal bead, except for Exocelina piusi sp. n., which has narrow but distinct pronotal bead and seems to form a separate lineage. There are two monophyletic complexes in the clade: 1) E. casuarina, E. fume, and E. ibalimi sp. n. with a large, hook-like anterolateral seta of the male protarsomere 4 and 2) E. keki sp. n. and E. pseudofume sp. n. with a thin, long, slightly curved anterolateral seta of the male protarsomere 4, as well as E. messeri and E. sima sp. n., which also have a similar shape of this seta. The representatives of this clade best demonstrate a "swollen" apex of the median lobe.
Clade IV is the most homogeneous and includes the smallest in size species of the group. They are morphologically very similar, and three of them, E. cyclops sp. n., E. bewani sp. n., and E. adelbertensis sp. n., are a good example of recent allopatric speciation along the north coast of New Guinea (Toussaint et al. 2014).
Clade V includes two very different species. Exocelina menyamya sp. n. is the most uncharacteristic representative of the group because the apex of its median lobe is thin, flattened, and with ventral impression. The second species is E. pusilla sp. n., one of the smallest species of the group. Based on its size and coloration, this species could have been placed into the clade IV but the molecular analysis, as well as the shape of its median lobe, showed that it is a separate lineage of inland mountain Exocelina. Most likely E. pseudopusilla sp. n. belongs to this clade too. This species is very similar to E. pusilla sp. n., but larger and more elongate, with denser and coarser dorsal punctation and microreticulation and different shape of the median lobe (for more details on species delimitation, see the species descriptions). Exocelina pusilla sp. n. has wider distribution. Both species are known from the Mount Wilhelm, but from different altitudes: E. pusilla sp. n. only from 200 m (from other localities, it is known from up to 500 m) and E. pseudopusilla sp. n. only from 1200 m. If this species delimitation is correct, then this is the first distinct example in Exocelina of altitudinal peripatric speciation, which is also assumed for the Exocelina species of Weyland area (Toussaint et al. 2014).
Thus, this group, as defined now, is the subject of further study and may be divided into subgroups or even groups as and when additional species are discovered.  Coloration: Brownish, with head and pronotum paler. Head reddish brown, darker posterior to eyes. Pronotum reddish brown on sides, dark brown on disc. Elytra brown. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 14).
Structures: Pronotum with lateral bead. Its lateral sides with longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 slightly truncate.
Female: Unknown. Affinities. Exocelina adelbertensis sp. n. is very similar to E. sumokedi sp. n. and E. bewani sp. n. but it has slightly more strongly impressed microreticulation, therefore, dorsal surface is distinctly less shiny. Median lobe is more thickened, similar to that of E. sumokedi sp. n. but its apex is curved downwards and with stronger terminal angulation. The species is also similar to E. cyclops sp. n., E. pseudopusilla sp. n., and E. pusilla sp. n., see their "Affinities" and the "Key". 5 slightly concave ventrally, with anterior band of ca 70 and posterior band of ca 30 relatively long setae (Fig. 45D). Median lobe in lateral view short, slightly curved, and evenly tapering to dully pointed apex, apex not bent downwards; in ventral view, almost subparallel and distally slightly narrowed to apex, apex roundly truncate. Paramere slightly concave on dorsal side, with long, dense subdistal setae, proximal ones finer ( Fig. 45A-C). Abdominal ventrite 6 with 13-15 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina ambua sp. n. is similar to E. mendiensis sp. n. but differs from it in smaller size, coarser and denser dorsal punctation and microreticulation, and shape of the median lobe.
Distribution. Papua New Guinea: Southern Highlands Province. The species is known only from the type locality (Fig. 50).
Etymology. The species is named after Mt Ambua. The name is a noun in the nominative singular standing in apposition. Coloration: Brownish, with head and pronotum paler. Head reddish brown to brownish, sometimes paler anteriorly. Pronotum reddish brown on sides, brown to dark brown on disc. Elytra brown to dark brown, sometimes with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 13).
Structures: Pronotum with lateral bead. Its lateral sides with shallow longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, narrowly rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 slightly truncate.
Male: Antennae simple (Fig. 13). Protarsomere 4 with medium-sized, thick, curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior row of 21 and posterior row of 4 relatively short setae (Fig. 37D). Median lobe in lateral view slightly curved, with slightly thickened, angulate, and curved downwards apex; in ventral view, subparallel, with broad and slightly concave apex. Paramere slightly concave on dorsal side and with dense setae on subdistal part; proximal setae sparser . Abdominal ventrite 6 with 3 or 4 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina bewani sp. n. is very similar to E. sumokedi sp. n. but is larger and has a less striated abdominal ventrite 6; also, its median lobe is not narrowed distally in ventral view and with apex broad and slightly concave ventrally and curved downwards in lateral view. The species is also similar to E. adelbertensis sp. n., E. cyclops sp. n., E. pseudopusilla sp. n., and E. pusilla sp. n., see their "Affinities" and the "Key".
Distribution. Papua New Guinea: Sandaun Province. The species is known only from the type locality (Fig. 50).
Etymology. The species is named after the Bewani Mountains. The name is a noun in the nominative singular standing in apposition.
Affinities. Exocelina casuarina is the only species of the casuarina-group in Nabire Regency. In this area, Exocelina is represented mainly by the species of the ekari-group, which are small in size and have no pronotal bead. From them, as well as from E. ransikiensis Shaverdo et al., 2016d with the same characters, the species differs in larger size and the different shape of the median lobe. From E. bagus ((Balke & Hendrich, 2001), in Balke (2001)), which is similar in size and surface sculpture to E. casuarina, the species differs in simple male antennae and the different shape of the median lobe. From E. damantiensis  of the danae-group, the only species with the pronotal bead in the Nabire-Enarotali area, E. casuarina differs in absence of the pronotal bead, evidently stronger dorsal punctation and microreticulation, and the different shape of the median lobe.
Within the casuarina-group, the species is more similar to E. fume ) and E. ibalimi sp. n., with which it shares not only absence of the pronotal bead, but also a large, strongly curved anterolateral hook-like seta of the male protarsomere 4 (see their "Affinities" and the "Key").
Distribution. Papua: Nabire Regency. The species is known only from the area close to the type locality (Fig. 50). Coloration: Reddish. Dorsal surface almost uniformly yellowish red to reddish brown, with paler anterior part of head and pronotum laterally; head appendages and legs yellowish red (Fig. 12). All type specimens are teneral, therefore, coloration may be darker.
Structures: Pronotum with lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 slightly truncate.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina cyclops sp. n. is similar to E. sumokedi sp. n., E. adelbertensis sp. n., and E. bewani sp. n., but has coarser dorsal punctation. In this character, the species is more similar to E. pusilla sp. n. and E. pseudopusilla sp. n. but it differs from them in much broader and differently shaped median lobe (not distinctly narrowed distally, with apex thicker in lateral and ventral views) and from the latter, also in smaller size and slightly shinier dorsal surface.
Distribution. Papua: Jayapura Regency. The species is known only from the Cyclops Mountains (Fig. 50).
Etymology. The species is named after the Cyclops Mountains. The name is a noun in the nominative singular standing in apposition. (Balke, 1999) Figs 15, 39
Diagnosis. For complete description, see Balke (1998: 330). Beetle medium-sized: TL-H 3.7-4.4 mm; oblong-oval; brown to dark brown, with reddish brown pronotal sides, head, and sometimes also sides of elytra, in some specimens, disc of pronotum and elytron almost piceous; submatt, with fine but rather dense punctation and strongly impressed microreticulation; pronotum without lateral bead; male antennae simple (Fig. 3); male protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta; male protarsomere 5 long and narrow, with anterior band of more than 60 and posterior row of 6 relatively long, thin setae (Fig. 27D); median lobe in lateral view slightly curved, with apex curved downwards, with visible angle on dorsal side, in ventral view, distally distinctly narrowed to truncate apex; paramere slightly concave on dorsal side and with long, dense, thin setae, situated along dorsal margin: subdistal setae strong and dense, setae in middle part shorter and sparser, proximal setae long, only slightly sparser than subdistal ones ( Fig. 27A-C).
Affinities. In the area of its distribution, E. fume co-occurs with E. takime  and species of the ekari-, aipo-, okbapensis-, aipomek-, erteldi-, and danae-groups. From species of the ekari-group, the species differs in larger size, evidently stronger dorsal punctation and microreticulation, and the shape of the median lobe. In the lat-ter two characters, E. fume differs also from the species of the remaining groups, as well as in absence of the pronotal bead and simple male antennae.
Within the casuarina-group, the species is more similar to E. casuarina and E. ibalimi sp. n., especially the latter one, from which can be distinguished by paler coloration and the shape of the median lobe (see their "Affinities" and the "Key").
Distribution. Papua: Pegunungan Bintang. The species is known only from the type locality (Fig. 50).
Affinities. In the Herzog Range area, E. heidiae co-occurs with Exocelina jasminae , two species of the ekari-group, and four species of the danae-group. From all of them, the species differs in larger size and the shape of the median lobe. Additional characters for the species separations are presence of the pronotal bead, simple male antennae, and dorsal punctation and microreticulation.
Within the casuarina-group, the species is more similar to E. simbaijimi sp. n. (see its "Affinities" and the "Key").

Exocelina ibalimi
Coloration: Brown to piceous, with head and pronotum paler. Head reddish brown to piceous, darker posteriorly. pronotum reddish brown to piceous, broadly paler on lateral sides and sometimes also narrowly anteriorly and posteriorly. Elytra uniformly brown to piceous. Head appendages and legs yellowish red to reddish brown, legs distally darker, especially metathoracic legs (Fig. 4). Teneral specimens paler.
Surface sculpture: Submatt dorsally. Head with rather dense punctation (spaces between punctures 1-2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum and elytra with fine but rather dense punctation, sparser and finer than on head. Pronotum and elytra with strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine sparse punctation.
Structures: Pronotum without lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 broadly rounded or slightly truncate.
Male: Antennae simple (Fig. 4). Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior band of more than 80 and posterior row of 11 relatively long, thin setae (Fig. 28D). Median lobe in lateral view slightly curved, its apex rounded and not or only very slightly curved downwards; in ventral view, distally distinctly narrowed to truncate apex. Paramere slightly concave on dorsal side and with long, dense, thin setae situated along dorsal margin: subdistal setae denser, proximal setae sparser, setae in middle shorter, thinner ( Fig. 28A-C). Abdominal ventrite 6 with 7-11 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Variability. The species has variability in size, coloration and shape of the median lobe. Beetles are small to medium-sized (see the measurements above) and with coloration: from reddish head and pronotum and dark brown elytra to uniformly piceous with reddish brown pronotal sides. Median lobe shows different shape of its apex: in lateral view, it is not curved or differently slightly curved downwards reminding that of E. fume but without distinct angle.
Affinities. Exocelina ibalimi sp. n. is very similar to E. fume but differs from it in shape of the median lobe: its apex not curved or only slightly curved downwards, more or less rounded in lateral view, without distinct angle on the dorsal side. The species also has dorsal punctation distinctly finer and microreticulation less strongly impressed than in E. fume.
Etymology. The species is named for Sentiko Ibalim, one of the great young PNG entomologists, who collected most of these beetles. The species name is a noun in the genitive case. Coloration: Reddish to reddish brown, with head and pronotum paler. Head yellowish red to reddish brown, with small darker areas posterior to eyes. Pronotum yellowish red to reddish brown, with small brown to dark brown area on disc. Elytra reddish brown to brown, with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 6). Teneral specimens paler.

Exocelina keki
Surface sculpture: Submatt dorsally. Head with rather dense punctation (spaces between punctures 1-2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum and elytra with dense, distinct but fine punctation, sparser and finer than on head. Pronotum and elytra with strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine sparse punctation.
Structures: Pronotum without lateral bead, in few specimens with its traces in posterior part. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 rounded.
Male: Antennae simple (Fig. 6). Protarsomere 4 with anterolateral seta thin, long, smaller than more laterally situated large setae, slightly curved downwards. Protarsomere 5 long and narrow, with anterior band of more than 40 and posterior row of 7 relatively long, thin setae (Fig. 30D). Median lobe in lateral view almost straight, its apex rounded and not curved downwards; in ventral view, distally distinctly narrowed before rounded, narrow apex. Paramere slightly concave on dorsal side and with dorsal setae distinctly divided to long, dense subdistal setae and sparser proximal ones ( Fig.  30A-C). Abdominal ventrite 6 with 3-5 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Distribution and variability. Papua New Guinea: Madang and Eastern Highlands (Fig. 50). The species is known mainly from Keki area in Adelbert Mountains; only one beetle was collected in Bena, Eastern Highlands. It shows no morphological difference from the specimens of Keki populations, except for a small difference in the median lobe shape, which could be an expression of species variability. The species might have the same pattern of distribution as Exocelina brahminensis Shaverdo et al., 2012, which has a wide distribution in the Momase Region and is known from Adelbert Mountains and Bena.
Affinities. Exocelina keki sp. n. is very similar to Exocelina messeri (Balke, 1999) in body form and coloration, but has much more distinct dorsal punctation and stronger microreticulation, as well as median lobe more slender, with apex smaller and narrower in ventral view; the ventral setae of male protarsomere 5 are much less numerous and clearly divided into anterior band and posterior row.
Etymology. The species is named after Keki Village. The name is a noun in the nominative singular standing in apposition. Description. Body size and form: Beetle large: TL-H 5.4 mm, TL 6.0 mm, MW 2.9 mm, with broader, oblong-oval habitus.
Surface sculpture: Submatt dorsally. Head with dense, coarse punctation (no spaces between punctures or spaces of equal size of punctures), finer and sparser anteriorly; diameter of punctures equal to diameter of cells of microreticulation. Pronotum with relatively dense but fine punctation, sparser and finer than on head. Elytra with finer punctation than on pronotum. Pronotum and elytra with strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles, abdominal ventrites with distinct microreticulation and strioles. Metaventrite medially, metacoxal plates, and abdominal ventrites with fine, sparse punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively short, broad, slightly convex and smooth in the middle, with distinct lateral bead and few lateral setae, lateral sides flattened. Abdominal ventrite 6 rounded.
Male: Antennae simple (Fig. 25). Protarsomere 4 with anterior angle slightly expanded, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 slightly concave ventrally, with anterior band of ca 100 and posterior band of ca 40 relatively long setae (Fig. 49D). Median lobe in lateral view long, slightly curved, with small, very slightly bent downwards, thickened apex; in ventral view, evenly tapering to broadly pointed apex. Paramere slightly concave on dorsal side and with weak dorsal setation, setae on subdistal part stronger, denser, more evident than proximal setae ( Fig. 49A-C). Abdominal ventrite 6 with 17-18 lateral striae on each side.
Female: Unknown. Affinities. Exocelina kumulensis sp. n. is similar to E. mendiensis sp. n. but differs from it by being larger, having coarser and denser dorsal punctation and by the shape of the median lobe.
Distribution. Papua New Guinea: Enga Province. The species is known only from the type locality (Fig. 50).
Etymology. The species is named after Kumul Lodge. The name is an adjective in the nominative singular. Coloration: Piceous. Head piceous, narrowly brownish anteriorly and sometimes with two brownish spots between eyes. Pronotum piceous, brownish laterally and anteriorly. Elytra piceous, sometime with narrow brownish sutural lines. Head appendages and legs proximally reddish brown, legs distally darker, brownish, especially metathoracic legs (Fig. 24).

Exocelina mendiensis
Surface sculpture: Submatt dorsally. Head with relatively dense punctation (no spaces between punctures or spaces 2 times size of punctures), sparser anteriorly, denser and coarser between eyes; diameter of punctures smaller than or equal to diameter of cells of microreticulation. Pronotum with relatively dense but fine punctation, sparser and finer than on head. Elytra with very fine, sparse punctation. Pronotum and elytra with rather strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles, abdominal ventrites with distinct microreticulation and strioles. Metaventrite medially, metacoxal plates, and abdominal ventrites with very fine, sparse punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, and smooth, with distinct lateral bead and few lateral setae. Abdominal ventrite 6 slightly truncate.
Male: Antennae simple (Fig. 24). Protarsomere 4 with anterior angle slightly expanded, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 with anterior band of more than 60 and posterior row of 16 relatively long setae (Fig. 48D). Median lobe in lateral view long, slightly curved, with small, slightly bent downwards, thickened apex; in ventral view, evenly tapering to broadly pointed apex. Paramere slightly concave on dorsal side and with weak dorsal setation, setae on subdistal part stronger and denser than proximal setae (Fig. 48A-C). Abdominal ventrite 6 with 23-27 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina mendiensis sp. n. is similar to the larger species of the group, E. kumulensis sp. n. and E. ambua sp. n., but differs from them in its darker coloration, shinier dorsal surface and shape of the median lobe. Also, see under E. okapa sp. n.
Distribution. Papua New Guinea: Southern Highlands Province. The species is known only from the type locality (Fig. 50).
Etymology. The species is named after Mendi Village. The name is an adjective in the nominative singular. Coloration: Brown, with reddish pronotum. Head brown, with slightly darker areas posterior to eyes. Pronotum broadly reddish laterally and dark brown medially from anterior to posterior margins. Elytra uniformly brown, in the middle with traces of narrow reddish sutural lines. Head appendages and legs proximally yellowish red, legs distally darker, reddish brown, especially metathoracic legs (Fig. 20).

Exocelina menyamya
Surface sculpture: Matt dorsally. Head with rather dense, coarse punctation (spaces between punctures 1-2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures smaller than or equal to diameter of cells of microreticulation. Pronotum and elytra with distinct punctation, sparser and finer than on head. Pronotum and elytra with strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine sparse punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively short, broad, slightly convex and smooth in the middle, with distinct lateral bead and few lateral setae, lateral sides slightly flattened. Abdominal ventrite 6 slightly truncate.
Male: Antennae simple (Fig. 20). Protarsomere 4 with large, thick, slightly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of more than 50 and posterior row of 13 relatively long, thin setae (Fig. 44D). Median lobe in lateral view narrowed to apex, with thin, slightly curved upwards apex; in ventral view, narrowed before apex, with apex rounded, of shape of a baby pacifier, with distinct ventral impression. Paramere slightly concave on dorsal side and with long, dense, thin setae situated along dorsal margin, subdistal setae denser, proximal setae much sparser, setae in middle shorter, thinner ( Fig. 44A-C). Abdominal ventrite 6 with 19-22 lateral striae on each side.
Female: Unknown. Affinities. Exocelina menyamya sp. n. is similar to E. casuarina and E. fume in body size, shape, and coloration but can be distinguished from them by the completely different shape of the median lobe and presence of the pronotal bead.
Distribution. Papua New Guinea: Morobe Province. The species is known only from the type locality (Fig. 50).
Etymology. The species is named after Menyamya Village. The name is a noun in the nominative singular standing in apposition.
Diagnosis. For complete description, see Balke (1999: 274-275). Beetle small: TL-H 3.2-3.7 mm; oblong-oval, more strongly attenuated posteriorly; reddish to reddish brown, with head and pronotum slightly paler; shiny, with very fine, sparse punc-tation, almost invisible on elytra and weakly impressed microreticulation; pronotum without lateral bead, sometimes with its traces in posterior part; male antennae simple (Fig. 5); male protarsomere 4 with anterolateral seta thin, long, smaller than more laterally situated large setae, slightly curved downwards; male protarsomere 5 long and narrow, with more than 80 relatively long, thin setae, which divided in anterior and posterior ones proximally and mixed up together in distal half of tarsomere (Fig. 29D); median lobe in lateral view almost straight, its apex rounded and not curved downwards, in ventral view, distally narrowed before apex, apex broad, slightly rounded; paramere slightly concave on dorsal side and with dorsal setae distinctly divided into long, dense subdistal setae and sparser, rather inconspicuous proximal ones, setae in middle part short and fine ( Fig. 29A-C).
Affinities. See under E. keki sp. n. Distribution. Papua New Guinea: East Sepik Province. The species is known only from the type locality (Fig. 50). Coloration: Piceous, with reddish brown pronotum. Head reddish brown to piceous, paler anteriorly and darker posterior to eyes. Pronotum dark brown to piceous, with reddish to reddish brown sides narrowly or broadly. Elytra dark brown to piceous, sometime with narrow reddish sutural lines. Head appendages and legs proximally yellowish red, legs distally darker, reddish brown, especially metathoracic legs (Fig. 23). Teneral specimens paler.

Exocelina okapa
Surface sculpture: Shiny dorsally. Head mostly with fine, sparse punctation (spaces between punctures 2-3 times size of punctures) but punctation denser and coarser between eyes; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum and elytra with very fine, sparse punctation, sometimes inconspicuous on elytra. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles, abdominal ventrites with distinct microreticulation and strioles. Metaventrite medially, metacoxal plates, and abdominal ventrites with very fine, sparse, often inconspicuous punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, and smooth, with distinct lateral bead and few lateral setae. Abdominal ventrite 6 rounded.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina okapa sp. n. is similar to E. yoginofi sp. n. but differs from it in very weak dorsal punctation and microreticulation and more slender median lobe. The species is also similar to E. mendiensis sp. n. but differs from it in distinctly smaller size and differently shaped apex of the median lobe.
Surface sculpture: Submatt dorsally. Head with fine, sparse punctation (spaces between punctures 2-3 times size of punctures), only with some larger punctures between eyes; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum and elytra with very fine, sparse punctation. Pronotum and elytra with rather strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine, sparse punctation.
Structures: Pronotum with narrow lateral bead. Its lateral sides with inconspicuous, shallow longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 rounded.
Male: Antennae simple (Fig. 9). Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior band of ca 40 and posterior row of 6 relatively long, thin setae (Fig. 33D). Median lobe in lateral view slightly curved, broad, with apex bent downwards, not distinctly thickened, slightly angulate; in ventral view, almost subparallel and distally distinctly narrowed to apex, apex roundly truncate, of shape of a baby pacifier. Paramere slightly concave on dorsal side, with long, dense dorsal setae: subdistal setae strong and dense, setae in middle part shorter and sparser, proximal setae longer and stronger than subdistal ones ( Fig. 33A-C). Abdominal ventrite 6 with 9-10 lateral striae on each side.
Female: Unknown. Affinities. Exocelina piusi sp. n. is similar to E. messeri and, especially, to E. pseudofume sp. n. in body shape, coloration, and dorsal punctation and microreticulation, but differs from them in presence of narrow pronotal bead and shape of the median lobe.
Etymology. The species is named for Pius, a local collector. The species name is a noun in the genitive case. Description. Body size and form: Beetle medium-sized: TL-H 3.3-3.6 mm, TL 3.6-3.95 mm, MW 1.8-2.0 mm (holotype: TL-H 3.3 mm, TL 3.6 mm, MW 1.9 mm), with oblong-oval habitus.

Exocelina pseudofume
Coloration: Reddish to reddish brown, with head and pronotum paler. Head yellowish red to reddish brown, with small darker areas posterior to eyes. Pronotum yellowish red to reddish brown, darker (to brown) on disc. Elytra reddish brown to brown, sometimes with narrow yellowish or reddish sutural lines. Head appendages and legs yellowish red, legs distally darker, especially metathoracic legs (Fig. 7). All specimens are slightly teneral, therefore, the species coloration might be more darker.
Surface sculpture: Shiny dorsally. Head with rather dense punctation (spaces between punctures 1-2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures smaller than diameter of cells of microreticulation or equal to it. Pronotum and elytra with very distinct punctation, sparser and slightly finer than on head. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine sparse punctation.
Structures: Pronotum without lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 rounded.
Male: Antennae simple (Fig. 7). Protarsomere 4 with anterolateral seta thin, long, smaller than more laterally situated large setae, slightly curved downwards. Protarsomere 5 long and narrow, with anterior band of ca 40 and posterior row of 10 relatively long setae (Fig. 32D). Median lobe in lateral view slightly curved, its apex strongly bent downwards, with visible angle on dorsal side; in ventral view, almost subparallel and distally narrowed to truncate apex. Paramere slightly concave on dorsal side and with long, dense, thin setae, situated along dorsal margin: subdistal setae denser than setae in middle and proximal parts (Fig. 32A-C). Abdominal ventrite 6 with 5-8 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina pseudofume sp. n. is similar to E. messeri and E. keki sp. n. but it has distinctly broader and more oval habitus, shinier dorsal surface due to weaker microreticulation, as well as median lobe of different shape: thicker, with apex broader and curved downwards, with visible angle on dorsal side in lateral view. The shape of median lobe is similar to that of E. fume.
Distribution. Papua New Guinea: Madang (Fig. 50). Etymology. The species is named "pseudofume" because shape of its median lobe remains that of E. fume. The name is a noun in the nominative singular standing in apposition. Description. Body size and form: Beetle small: TL-H 3.25-3.55 mm, TL 3.65-3.95 mm, MW 1.8-1.85 mm (holotype: TL-H 3.5 mm, TL 3.85 mm, MW 2.0 mm), with oblong to oblong-oval habitus.

Exocelina pseudopusilla
Coloration: Reddish brown to dark brown, with head and pronotum paler. Head reddish to reddish brown, with small darker areas posterior to eyes. Pronotum reddish to reddish brown, with dark brown disc. Elytra brown to dark brown, with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 18). Teneral specimens paler.
Surface sculpture: Submatt dorsally. Head with dense, coarse punctation (no spaces between punctures or spaces of equal size of punctures), evidently finer and sparser anteriorly; diameter of punctures equal to or larger than diameter of cells of microreticulation. Pronotum and elytra with dense and coarse punctation, sparser and finer than on head. Pronotum and elytra with rather strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and fine sparse punctation.
Structures: Pronotum with narrow lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 slightly truncate or very slightly concave.
Male: Antennae simple (Fig. 18). Protarsomere 4 with anterior angle slightly expanded, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior band of ca 40 and posterior row of 13 relatively long, thin setae (Fig. 42D). Median lobe in lateral view simple, slightly curved; in ventral view, evenly tapering to broadly pointed apex, side of apex slightly thickened. Paramere slightly concave on dorsal side and with dense setae on subdistal part; proximal setae finer ( Fig. 42A-C). Abdominal ventrite 6 with 9-10 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina pseudopusilla sp. n. is similar to E. pusilla sp. n. but larger, more elongate, with denser and coarser dorsal punctation and microreticulation and differently shaped median lobe. See also under E. cyclops sp. n.
Distribution and note on taxonomy. Papua New Guinea: Simbu Province (Fig. 50). So far, this species is known only from the Mount Wilhelm, where it occurs at the high altitudes (1200 m), whilst E. pusilla sp. n. is also known from the Mount Wilhelm but only from 200 m. We consider the specimens from 1200 m as a distinct species (not belonging to E. pusilla sp. n.) because of the morphological differences mentioned above and because no intermediate forms were found. We realize a possibility that they might be just a larger, more elongate, and more strongly punctured and reticulated form of E. pusilla sp. n. adapted to the high altitudes. However, based on the present material, we cannot confirm it. For that, further morphological and molecular studies and more material, including one from intermediate altitudes, are requited.
Etymology. The species was mistaken for E. pusilla sp. n. due to their similarity. The name is a noun in the nominative singular standing in apposition. Coloration: Reddish to reddish brown, with head and pronotum paler. Head yellowish red to reddish, with small darker areas posterior to eyes. Pronotum yellowish red to reddish, with small brownish area on disc. Elytra reddish brown to brown, with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 10). Teneral specimens paler.

Exocelina pusilla
Surface sculpture: Shiny dorsally. Head with dense, coarse punctation (no spaces between punctures or spaces 2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures equal to or larger than diameter of cells of microreticulation. Pronotum and elytra with dense and coarse punctation, sparser and finer than on head. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and fine sparse punctation.
Structures: Pronotum with narrow lateral bead. Its lateral sides with longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 slightly truncate or very slightly concave.
Male: Antennae simple (Fig. 10). Protarsomere 4 with anterior angle slightly expanded and large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, with anterior band of ca 40 and posterior row of 12 relatively long, thin setae (Fig. 35D). Median lobe in lateral view simple, slightly curved; in ventral view, evenly tapering to broadly pointed apex, side of apex slightly thickened. Paramere slightly concave on dorsal side and with dense setae on subdistal part; proximal setae finer and much sparser (Fig. 35A-C). Abdominal ventrite 6 with 5-10 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina pusilla sp. n. is very similar to E. cyclops sp. n. in body shape, coloration, and surface sculpture but differs in having distinctly thinner and distally narrowed median lobe. It is also similar to E. adelbertensis sp. n., E. bewani sp. n., and E. sumokedi sp. n. but has coarser dorsal punctation and differently shaped median lobe. See also under E. pseudopusilla sp. n.
Distribution. Papua New Guinea: Madang and Simbu Provinces (Fig. 50). Etymology. The species name derives from the Latin "pusillus" (small, tiny) to express small size of these beetles. The species name is an adjective in the nominative singular. Coloration: Reddish brown head and pronotum and piceous elytra. Head reddish in its anterior half and dark brown in posterior one. Pronotum dark brown on disc and gradually paler to yellowish red laterally. Elytra dark brown, paler laterally and almost piceous on disc. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 8).

Exocelina sima
Surface sculpture: Shiny dorsally. Head with rather dense punctation (spaces between punctures 1-2 times size of punctures) but fine punctation; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum and elytra with distinct punctation, sparser and finer punctation than on head. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation stronger. Metaven-trite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and very fine sparse punctation.
Structures: Pronotum without lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, elongate, relatively broad, slightly convex, with distinct lateral bead and few. Abdominal ventrite 6 rounded.
Male: Antennae simple (Fig. 8). Protarsomere 4 with anterolateral seta long and thin, equal to more laterally situated large setae, slightly curved downwards. Protarsomere 5 long and narrow, with anterior band of more than 40 and posterior row of 12 relatively long, thin setae (Fig. 31D). Median lobe in lateral view short, slightly curved, with enlarged, rounded, not bent downwards apex; in ventral view, narrow, subparallel, and with truncate apex. Paramere very slightly concave on dorsal side and with long, dense, thin setae, situated along dorsal margin: subdistal setae strong and dense, setae in middle part shorter and sparser, proximal setae long but sparser than subdistal ones ( Fig.  31A-C). Abdominal ventrite 6 without lateral striae on each side, except one with setae.
Affinities. In absence of the pronotal bead and thin and not hook-like anterolateral seta of the male protarsomere 4, Exocelina sima sp. n. is similar to E. keki sp. n., E. messeri, and E. pseudofume sp. n. However, the species distinctly differs from them in more oval body form and more strongly expressed bicolor dorsal surface: reddish head and pronotum and piceous elytra, as well as in a characteristic shape of the median lobe and male abdominal ventrite 6 without lateral striae. The latter character is unique among New Guinea Exocelina.
Distribution. Papua New Guinea: Simbu and Eastern Highlands Provinces, Crater Mountain. This species is known only from the type locality (Fig. 50).
Etymology. The species is named after Sima River. The name is a noun in the nominative singular standing in apposition.

Affinities.
Exocelina simbaiensis sp. n. is similar to E. yoginofi sp. n. in body form, size, and coloration, but differs from it in distinctly stronger punctation and microreticulation and in thickened apex of the median lobe.
Coloration: Piceous, with head and pronotum paler. Head dark brown to piceous, reddish brown to brown anteriorly, with small darker areas posterior to eyes. Pronotum reddish brown to brown laterally and piceous on disc. Elytra brown to piceous, sometimes with narrow reddish sutural lines. Head appendages and legs proximally reddish, legs distally darker, brown, especially metathoracic legs (Fig. 17). Teneral specimens paler.
Surface sculpture: Submatt dorsally. Head with rather dense, coarse punctation (spaces between punctures 1-2 times size of punctures), evidently finer and sparser anteriorly; diameter of punctures smaller than or equal to diameter of cells of microreticulation. Pronotum with distinct punctation, sparser and finer than on head. Elytra with very fine and sparse punctation. Pronotum and elytra with strongly impressed microreticulation. Head with microreticulation stronger. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and fine, sparse punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, and smooth, with distinct lateral bead and few lateral setae. Abdominal ventrite 6 slightly truncate or broadly rounded.
Male: Antennae simple (Fig. 17). Protarsomere 4 with anterior angle slightly expanded, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 long and narrow, slightly concave ventrally, with anterior band of more than 80 and posterior band of ca 30 relatively long setae (Fig. 41D). Median lobe in lateral view evenly broad, with rounded, slightly angulated, thickened apex; in ventral view, almost subparallel, with broadly rounded apex, with thickened margins. Paramere slightly concave on dorsal side and with long, dense, thin setae situated along dorsal margin: subdistal setae denser, proximal setae sparser, setae in middle finer ( Fig. 41A-C). Abdominal ventrite 6 with 9-14 lateral striae on each side.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina simbaijimi sp. n. is similar to E. heidiae in body size and form but differs from it in darker coloration, more distinct dorsal punctation, broader median lobe, with more angulated apex in lateral view and more thickened margins in ventral view.
Distribution. Papua New Guinea: Western Highlands Province (Fig. 50). Etymology. The species is named after Simbai-Jimi area. The name is a noun in the nominative singular standing in apposition. Coloration: Brownish, with head and pronotum paler. Head yellowish red to reddish brown in anterior half and brown to dark brown in posterior ones. Pronotum yellowish red to reddish brown on sides, brown to dark brown on disc. Elytra brown to dark brown, with narrow reddish sutural lines. Head appendages yellowish red, legs reddish, distally darker, especially metathoracic legs (Fig. 11). Teneral specimens paler.
Structures: Pronotum with lateral bead. Its lateral sides with shallow longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 broadly rounded or slightly truncate.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina sumokedi sp. n. is similar to E. pusilla sp. n. but is smaller, darker, more oval, shinier, with finer and sparser dorsal punctation and weaker microreticulation, with shallow longitudinal impressions on lateral sides of pronotum and different shape of the median lobe. The species is also similar to E. adelbertensis sp. n., E. bewani sp. n., E. cyclops sp. n., and E. pseudopusilla sp. n., see their "Affinities" and "Key".
Distribution. Papua: Puncak Regency. The species is known only from the Iratoi area (Fig. 50).

Exocelina yoginofi
Surface sculpture: Submatt dorsally. Head with rather dense punctation (spaces between punctures 1-2 times size of punctures), finer and sparser anteriorly; diameter of punctures smaller than or equal to diameter of cells of microreticulation. Pronotum and elytra with sparser and finer punctation than on head. Head, pronotum and elytra with rather strongly impressed microreticulation. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and fine, sparse but distinct punctation.
Structures: Pronotum with distinct lateral bead. Its lateral sides with distinct longitudinal impressions. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct lateral bead and few setae. Abdominal ventrite 6 rounded.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocelina yoginofi sp. n. is similar to E. simbaiensis sp. n. in body form, size, and coloration, but differs from it in distinctly finer punctation and microreticulation and in having the apex of the median lobe not thickened. Also, see under E. okapa sp. n.
Distribution. Papua New Guinea: Eastern Highlands Province (Fig. 50). Etymology. The species is named after Yoginofi Village. The name is a noun in the nominative singular standing in apposition.

Key to species of the Exocelina casuarina-group
The key is based mostly on the male characters. In many cases, females cannot be assigned to species due to similarity of their external and internal structures (for female genitalia see Figs 17a and 17b in Shaverdo et al. (2005)). Some species are rather similar in point of external morphology; therefore, in most cases the male genitalia need to be studied for reliable species identification. Numbers in brackets refer to an arrangement of the species descriptions above. Median lobe not or slightly narrowed before truncate or slightly concave apex in ventral view (Fig. 26A)  Beetle more oval, broader, with pronotum reddish brown and elytra piceous (Fig. 8). Median lobe shorter, almost parallel-sided in ventral view, with distinctly rounded apex in lateral view (Fig. 31A, B)  Dorsal punctation almost invisible on elytra (Fig. 5). Median lobe narrowed to slightly rounded, broad apex in ventral view (Fig. 29A). Ventral setae of male protarsomere 5 much more numerous, usually not divided into two rows/bands (Fig. 29D)  Beetle dark brown, with elytral punctation finer. Median lobe thinner and narrower in lateral view (Fig. 40 B)  Beetle dark brown to piceous, with elytral punctation more distinct. Median lobe thicker and broader in lateral view (Fig. 41 B)  Beetle smaller, TL-H 3.25-3.55 mm, reddish brown to dark brown (Fig. 18). Apex of median lobe slightly thickened, not bent downwards in lateral view (Fig. 42B)  Apex of median lobe not bent downwards in lateral view, roundly truncate in ventral view (Fig. 45B, A). Beetle matt, with strong dorsal microreticulation (Fig. 21)

Habitat
The studied species have the same habitat preferences as those described in Shaverdo et al. (2012). They are associated with running water, but avoid the current, i.e., their preferred microhabitats are small creeks, small and quiet backflows, puddles at the edge of streams and creeks, and other similar situations.  ) 3 E. fume  4 E. ibalimi sp. n.