Nine new species groups, 15 new species, and one new subspecies of New Guinea diving beetles of the genus Exocelina Broun, 1886 (Coleoptera, Dytiscidae, Copelatinae)

Abstract Nine new species groups of Exocelina Broun, 1886 from New Guinea are introduced with keys to their representatives. Four groups are monotypic and include three new species: the E. aipomek group, the E. koroba group: E. korobasp. nov., the E. mekilensis group: E. mekilensissp. nov., and the E. morobensis group: E. morobensissp. nov. The remaining five species groups include 18 species with 12 new species and one new subspecies: the E. bacchusi group: E. akamekusp. nov., E. oiwasp. nov., E. oksibilensissp. nov., and E. bacchusi herzogensisssp. nov.; the E. jaseminae group: E. asekisp. nov., E. kailakisp. nov., and E. pseudojaseminaesp. nov.; the E. larsoni group: E. warahulenensissp. nov.; the E. takime group: E. mianminensissp. nov.; and the E. warasera group: E. haiasp. nov., E. kobausp. nov., E. pulchellasp. nov., and E. waraserasp. nov. Diagnoses of five already described species of these groups are provided, as well as comparatives notes on all species. Exocelina santimontis (Balke, 1998) syn. nov. is a junior synonym of E. aipomek (Balke, 1998). Data on the distribution of the species are given, showing that most of the species of these groups occur in the Papua New Guinea.


Introduction
This paper introduces nine new species groups of Exocelina Broun, 1886, completing our assessment of the supraspecific classification of the genus in New Guinea. Four of the species groups here diagnosed are monotypic and include species with distinct morphological characters and which were inferred as separate lineages in our previous molecular phylogenetic analyses . One of these groups is proposed for the described species, Exocelina aipomek (Balke, 1998), and the three remaining for three new species. Five other groups are small and consist of two to five species. Four groups (the E. bacchusi, E. jaseminae, E. larsoni and E. takime groups) are proposed for already known species with the addition of eight new species and one new subspecies, and the fourth group, the E. warasera group, includes only four new species. We provide a diagnosis for the complex of groups treated herein and notes on their phylogeny, as well as morphological diagnoses for each group separately. All species of the groups are treated, including comparative notes and detailed descriptions for the new species. Identification keys are presented for the groups with more than one species. Including the results of this work, 140 species of Exocelina are now described from New Guinea and 195 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(Shaverdo et al. , 2018, all species data will be presented on the species-id.net portal automatically created by ZooKeys with the publication of this paper.

Materials and methods
The present work is based on material from the following collections:

General diagnostic characters of the treated groups and notes on their phylogeny
Here, we provide general diagnostic characters for all representatives of the groups, which can be used to separate them from some of the previously studied groups. To complete diagnoses, special diagnostic characters for each group, mainly based on shape of the median lobe and shape and setation of the parameres, are provided below, before the species treatments.
-beetles small or medium-sized (TL-H 2.85-4.5 mm); -habitus elongate to oval, in most species oblong-oval; with rounded pronotal and elytral sides, body outline continuous; -pronotum short, trapezoidal, with posterior angles not drawn backwards; -pronotum and elytra without striae or strioles; -antennomeres not modified, simple; -male protarsomeres 1-3 not expanded laterally; -male protarsomere 4 cylindrical, narrow, with a large, hook-like to thin, long, slightly curved anterolateral seta; -male protarsomere 5 not modified, long and narrow, sometimes slightly concave ventrally; -median lobe of aedeagus with continuous outline in ventral and lateral view; -ventral sclerite of median lobe more or less deeply divided apically.
Diagnosis. For complete description, see Balke (1998: 322). Beetle medium-sized (TL-H 4.0-4.35 mm), oblong-oval; piceous, sometimes with paler pronotal sides; dorsally shiny, with extremely fine, inconspicuous punctation and weakly impressed microreticulation; pronotum with distinct lateral bead (Fig. 1); male protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta; male protarsomere 5 ventrally with anterior band of more than 60 and posterior row of 14 relatively long setae (Fig. 5D); median lobe simple, in lateral view, evenly tapering to broadly pointed, somehow elongate and gently curved downwards apex, in ventral view, apex more or less rounded; paramere with distinct dorsal notch and large, long subdistal part, dorsal setae numerous and strong, subdistal slightly denser and longer than proximal ones, the latter more or less distinct ( Fig. 5A-C).
Variability. The species shows variability within and between populations in shape of the apex of the median lobe, which can be shorter or more elongate (Figs 6,7).

Exocelina koroba
Structures: Pronotum with distinct lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, slightly rounded and with few transverse strioles anteriorly, without anterolateral extensions. Blade of prosternal process lanceolate, relatively broad, convex, with distinct bead and few setae laterally. Abdominal ventrite 6 slightly truncate.
Distribution. Papua New Guinea: Hela Province, Koroba area (Fig. 11). Etymology. The species is named after Koroba Village. The name is a noun in the nominative singular standing in apposition.

Exocelina mekilensis group
This group is characterised by fine and sparse dorsal punctation; pronotum without lateral bead; median lobe of aedeagus without setation, simple; in lateral view, apex thick, short and slightly curved downwards, its minuscule tip curved upwards; apexes of ventral sclerites of median lobe slightly unequal: left one slightly longer that right one; paramere without dorsal notch, evenly tapering to distal part, with numerous small spines and without long setae.  species without pronotal bead (E. pseudobifidae , E. pseudoeme Shaverdo & Balke, 2014, and E. ibalimi Shaverdo & Balke, 2018, it can be differentiated by the shape and setation of its median lobe and paramere, which are very characteristic and resemble those of the E. ullrichi group . Distribution. Papua New Guinea: Sandaun Province (Fig. 11). Etymology. The species is named after Mekil Village where most specimens of the species were found. The name is an adjective in the nominative singular.
Colouration: Brown to dark brown, usually with reddish pronotum and head. Head reddish to brown, sometimes darker posterior eyes; pronotum reddish to brown, often broader or narrower darker area on disc; elytra brown to dark brown, sometimes with reddish sutural lines; head appendages and legs proximally reddish, legs distally darker, reddish brown to brown (Fig. 4). Teneral specimen paler.
Surface sculpture: Shiny dorsally, with fine, sparse punctation and weakly impressed microreticulation. Head with relatively fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures almost equal to or smaller than diameter of cells of microreticulation. Pronotum and elytra with much finer and sparser punctation than on head, often inconspicuous on elytra. Pronotum and elytra with weakly impressed microreticulation. Head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Venter with extremely inconspicuous punctation, more evident on metacoxal plates and two last abdominal ventrites.
Structures: Pronotum with narrow 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 bead and few setae laterally. Abdominal ventrite 6 very slightly truncate.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae. Affinities. From the species co-occurring in the same area (E. brahminensis Balke, 2012, E. damantiensis, andE. garaina Shaverdo &Balke, 2016), E. morobensis sp. nov. can be distinguished by its size, colouration, narrow pronotal bead, and shape and setation of the median lobe and paramere.
Distribution. Papua New Guinea: Morobe Province (Fig. 11). Etymology. The species is named after Morobe Province, the only province of PNG where the species has been found. The name is an adjective in the nominative singular.

Other groups Exocelina bacchusi group
The representatives of this group are characterised by fine to coarse dorsal punctation; pronotum with distinct lateral bead; median lobe of aedeagus without setation, simple, broadly pointed; apexes of ventral sclerites of median lobe almost equal; paramere evenly tapering to apex, proximal setae often longer and more distinct that subdistal. Colouration: Dark brown, with reddish pronotal sides and head anteriorly. Head reddish brown, paler anteriorly; pronotum dark brown on disc, with reddish sides; elytra dark brown, with weakly indicated reddish sutural lines; head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 13).

Exocelina akameku
Surface sculpture: Shiny dorsally, with weak and sparse punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures equal to or smaller than diameter of cells of microreticulation. Pronotum with much finer and sparser punctation than on head, very inconspicuous. Punctation on elytra invisible. Pronotum and elytra with weakly impressed microreticulation; head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Punctation on venter invisible; inconspicuous on two last abdominal ventrites.
Structures: Pronotum with narrow lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, very slightly rounded anteriorly. Blade of prosternal process lanceolate, relatively narrow, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 slightly truncate.
Male: Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of more than 30 and posterior row of 7 relatively long setae (Fig. 19D). Abdominal ventrite 6 with 7-8 lateral striae on each side. Median lobe short, robust, evenly tapering to slightly pointed apex in lateral and ventral views; apex slightly sinuate in lateral view (Fig. 19A, B). Paramere as in Fig. 19C.
Female: Unknown. Affinities. From the species co-occurring in the same area (from E. danae, E. ekari, E. broschii, and E. ullrichi groups), E. akameku sp. nov. can be distinguished by its size, dorsal punctation, and shape and setation of its median lobe and paramere. For the affinities within the group, see the "Key".

Exocelina bacchusi
Additional  Diagnosis. For complete description, see Balke (1998: 326). Beetle small to medium-sized: TL-H 3.05-3.9 mm, oblong-oval; dorsally uniformly reddish to dark brown or with paler head and sides of pronotum; shiny, with very fine to distinct punctation and usually weakly impressed microreticulation; pronotum with distinct lateral bead (Fig. 16); male protarsomere 4 with anterolateral seta very long and thin, evenly curved, smaller than more laterally situated large seta; male protarsomere 5 ventrally with anterior band of more than 50 and posterior row of 8 relatively long setae (Fig.  22D); median lobe simple, evenly attenuated to broadly pointed apex in lateral and ventral views; paramere very slightly concave on dorsal side and with long, dense, thin setae, situated along dorsal margin; proximal setae longer that subdistal, more distinct ( Fig. 22A-C).
Variability. The species shows variability in size, colouration, how strongly impressed dorsal punctation and, more seldom, microreticulation, and slightly in shape of the apex of the median lobe (Fig. 24).
Affinities. From the species co-occurring in the same area (E. craterensis Shaverdo & Balke, 2014, E. damantiensis (Balke, 1998), E. hintelmannae (Shaverdo, Sagata & Balke, 2005), E. sima, E. kobau sp. nov. and two species of the E. larsoni group), E. bacchusi can be distinguished by its reddish dorsal colouration and shape and setation of the median lobe and paramere. The most similar (in body size and form and colouration) to E. bacchusi are E. warasera sp. nov. and E. haia sp. nov., which occur with it. Only males of these species can be clearly separated by shape and setation of the median lobe and paramere; and therefore, dorsal setae of the paramere are important: in E. bacchusi, proximal setae longer that subdistal, more distinct. For the affinities within the group, see the "Key".
Distribution. Papua New Guinea: Madang, Simbu, Eastern Highlands, Morobe and Gulf Provinces (Fig. 25). This is one of the most abundant species in the region. Colouration: Yellow reddish to brown. Head reddish brown to brown, dark brown posterior to eyes. Pronotum yellowish reddish, with small dark area on disc or brown, with paler sides. Elytra yellow reddish to brown. Head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 17). Teneral specimen yellowish.
Structures: Pronotum with lateral bead. 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 bead and few setae laterally. Abdominal ventrite 6 slightly truncate.
Male: Protarsomere 4 with anterolateral seta rather long and thing, evenly curved, smaller than more laterally situated large seta. Protarsomere 5 ventrally with anterior band of more than 60 and posterior row of ten relatively long setae (Fig. 23D). Abdominal ventrite 6 with 6-8 lateral striae on each side. Median lobe simple, evenly tapering towards apex in lateral and ventral views; in lateral view, apex elongate, thin, with slightly enlarged, rounded tip (Fig. 23A, B). Paramere as in Fig. 23C.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Variability. Colouration of the specimens from Woitape distinctly paler, yellowish; the specimen form Wagau much darker, brown.
Affinities. From the nominotypical subspecies, it can be distinguished by shinier dorsal surface, shorter setae of male protarsomere 4, and by apex of the median lone elongate, thinner, with slightly enlarged tip. The further study is necessary to confirm the status of this taxon, which seems to replace the nominotypical subspecies in the Papuan Peninsula.
Etymology. The subspecies is named after Herzog Mts., where the subspecies was the first time discovered. The name is an adjective in the nominative singular.
Diagnosis. For complete description, see Balke (1998: 330). Beetle small (TL-H 3.45-3.75 mm), oblong-oval; brown to piceous, usually with paler pronotal sides; dorsally more or less shiny, with fine but conspicuous punctation and weakly impressed microreticulation; pronotum with distinct lateral bead (Fig. 14); male protarsomere 4 with anterolateral seta thin, weakly curved, smaller than more laterally situated large seta; male protarsomere 5 ventrally with anterior band of ca. 70 and posterior row of 6 relatively long setae (Fig. 20D); median lobe in lateral view evenly attenuated to elongate, thin apex, which slightly pointed in ventral view; paramere slightly concave on dorsal side and with distinct, long, dense, uniform setae, situated along dorsal margin ( Fig. 20A-C).
Affinities. The species can be distinguished from the species co-occurring in the same area (E. ascendens, E. aipomek, E. takime, the E. ekari group: E. eme Shaverdo and E. bifida, the E. danae group: E. damantiensis and E. danae, the E. okbapensis group: E. ketembang, E. talaki, and E. okbapensis, and all species of the E. aipo group) by body size and colouration, presence of pronotal bead, fine but conspicuous dorsal punctation, and shape and setation of its median lobe, paramere, and male protarsomere 4. For the affinities within the group, see the "Key".
Surface sculpture: Submatt dorsally, with strong and dense punctation and strongly impressed microreticulation. Head with dense and coarse punctation (spaces between punctures 0-1 times size of punctures); diameter of punctures equal to or larger than diameter of cells of microreticulation. Pronotum and elytra with finer and sparser punctation than on head, very distinct, more even on elytra. Pronotum and elytra with strongly impressed microreticulation; head with microreticulation stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate, but shiny. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Punctation on venter weak; more distinct on two last abdominal ventrites.
Structures: Pronotum with lateral bead. 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 bead and few setae laterally. Abdominal ventrite 6 broadly rounded or slightly truncate.
Male: Protarsomere 4 with anterolateral seta rather long and thin, evenly curved, equal to laterally situated large seta. Protarsomere 5 ventrally with anterior band of ca. 60 and posterior row of five relatively long setae (Fig. 18D). Abdominal ventrite 6 with 8-9 lateral striae on each side. Median lobe short, evenly tapering to apex in lateral and ventral views, very tip of apex thickened dorsally (Fig. 18A, B). Paramere as in Fig. 18D.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. From the species co-occurring in the same area (from E. danae, E. ekari, E. broschii, and E. ullrichi groups), E. oiwa sp. nov. can be distinguished by its size, dorsal punctation and colouration, shape and setation of its median lobe and paramere, and thin, evenly curved anterolateral seta of the protarsomere 4. The species is especially similar to E. aseki sp. nov., from which it can be distinguished by shape of its median lobe. For the affinities within the group, see the "Key".
Distribution. Papua New Guinea: Morobe Province (Fig. 25). Etymology. The species is named after Oiwa Village. The name is a noun in the nominative singular standing in apposition. Colouration: Reddish brown to brown. Head reddish brown to dark brown, paler anteriorly. Pronotum dark brown on disc and narrower or broader reddish on sides. Elytra reddish brown to dark brown, with reddish sutural lines. Head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 15).

Exocelina oksibilensis
Surface sculpture: Shiny dorsally, with fine punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures equal to or smaller than diameter of cells of microreticulation. Pronotum and elytra with much finer and sparser punctation than on head, sometimes inconspicuous. Pronotum and elytra with weakly impressed microreticulation; head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Punctation on venter invisible; inconspicuous on two last abdominal ventrites.
Structures: Pronotum with narrow lateral bead. 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 bead and few setae laterally. Abdominal ventrite 6 slightly truncate.
Male: Protarsomere 4 with anterolateral seta rather long and thing, evenly curved, smaller than more laterally situated large seta. Protarsomere 5 ventrally with anterior band of more than 60 and posterior row of 4 relatively long setae (Fig. 21D). Abdominal ventrite 6 with 3-6 lateral striae on each side. Median lobe simple, evenly tapering to broadly pointed apex in lateral and ventral views (Fig. 21A, B). Paramere as in Fig. 21C.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. The species is very similar to E. bacchusi in shape of the median lobe but can be distinguished from it by smaller size and egg-shaped habitus and shorter setae of male protarsomere 4. From the other species co-occurring in the same province (E. ascendens, E. aipomek, E. takime, the E. ekari group: E. eme Shaverdo and E. bifida, the E. danae group: E. damantiensis and E. danae, the E. okbapensis group: E. ketembang, E. talaki and E. okbapensis, and all species of the E. aipo group), it can be separated by body size and form, presence of pronotal bead, and the shape and setation of its median lobe, paramere, and male protarsomere 4. For the affinities within the group, see the "Key".

Exocelina jaseminae group
This group is characterised by fine to coarse dorsal punctation; pronotum with distinct lateral bead; median lobe of aedeagus without setation; in ventral view, with distinctly concave apex forming two apical lobes; in lateral view, apex tip prolongated into characteristic "nose"; apexes of ventral sclerites of median lobe almost equal or slightly unequal; paramere without distinct notch but slightly concave on dorsal side, its subdistal part with dense, strong setae, proximal setae inconspicuous. Description. Body size and form: Beetle small: TL-H 3.4 mm, TL 3.8 mm, MW 1.8 mm, with oblong-oval habitus.
Surface sculpture: Submatt dorsally, with strong and dense punctation and strongly impressed microreticulation. Head with dense and coarse punctation (spaces between punctures 0-1 times size of punctures); diameter of punctures equal to or larger than diameter of cells of microreticulation. Pronotum and elytra with finer and sparser punctation than on head, very distinct, more even on elytra. Pronotum and elytra with strongly impressed microreticulation; head with microreticulation stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate, but shiny. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Punctation on venter weak; more distinct on two last abdominal ventrites.
Structures: Pronotum with lateral bead. 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 bead and few setae laterally. Abdominal ventrite 6 broadly rounded.
Male: Protarsomere 4 with anterolateral seta very long and thin, evenly curved, in size equal to more laterally situated large seta. Protarsomere 5 ventrally with anterior band of ca. 80 and posterior row of ca. 16 relatively long setae, which mixed up medially (Fig. 30D). Abdominal ventrite 6 with 4-6 lateral striae on each side. Median lobe in lateral view with apical lobes distinct but shallow, slightly rounded, "nose" elongate, large (Fig. 30A, B). Paramere as in Fig. 30C.
Female: Unknown. Affinities. From the species co-occurring in the same area (from E. danae, E. ekari, E. broschii, and E. ullrichi groups), E. aseki sp. nov. can be distinguished by its size, dorsal punctation and colouration, shape and setation of its median lobe and paramere, and thin anterolateral seta of the male protarsomere 4. The species is especially similar to E. oiwa sp. nov., from which it can be distinguished by shape of its median lobe. For the affinities within the group, see the "Key".
Etymology. The species is named after Aseki Village. The name is a noun in the nominative singular standing in apposition.
Affinities. In the area of its distribution, E. jaseminae co-occurs with numerous species of the E. ekari, E. ullrichi, E. broschii, and E. danae groups. From them, this species can be distinguished by its size, dorsal colouration, surface sculpture, simple male antennae, presence of pronotal bead, and mainly by the shape of its median lobe. In its external appearance, E. jaseminae is especially similar to E. monae (Balke, 1998), from which can be distinguished by the shape of its median lobe. For the affinities within the group, see the "Key".
Distribution. Papua New Guinea: Eastern Highlands and Morobe Provinces (Fig. 34). Colouration: Piceous, with paler sides of pronotum and head anteriorly. Head reddish brown to dark brown, paler anteriorly. Pronotum dark brown, to piceous on disc and to reddish on sides. Elytra uniformly dark brown to piceous. Head appendages and legs proximally yellowish to reddish, legs distally darker, reddish brown (Fig. 28). Teneral specimen paler, brown to reddish brown with to yellowish pronotum and head.

Exocelina kailaki
Surface sculpture: Shiny dorsally, with extremely fine, sparse punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures smaller than diameter of cells of microreticulation. Pronotum with much finer and sparser punctation than on head, very inconspicuous. Punctation on elytra invisible. Pronotum and elytra with weakly impressed microreticulation; head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles. Punctation on venter invisible; inconspicuous on two last abdominal ventrites.
Structures: Pronotum with narrow lateral bead. 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 bead and few setae laterally. Abdominal ventrite 6 truncate.

Variability.
Shape of apex of the medial lobe varies. In some specimens, especially from Myola, it is not clearly truncate in lateral view but very slightly concave and, due to that, the "nose" is more distinct.
Affinities. Exocellina kailaki sp. nov. can be distinguished from the species of the E. danae group, E. nomax and E. pulchella sp. nov., co-occurring in the same area by its size, dorsal colouration and punctation, and shape and setation of its median lobe and paramere. For the affinities within the group, see the "Key".
Etymology. The species is named after Kailaki Village. The name is a noun in the nominative singular standing in apposition. Colouration: Brown to dark brown, with paler sides of pronotum and head. Head reddish brown, dark brown posterior to eyes. Pronotum reddish brown to brown, with reddish sides. Elytra brown to dark brown, sometimes with weak reddish sutural lines. Head appendages and legs proximally yellowish to reddish, legs distally darker, reddish brown (Fig. 29).

Exocelina pseudojaseminae
Surface sculpture: More or less shiny dorsally, with fine but distinct punctation and distinctly impressed microreticulation. Head with coarse and dense punctation (no spaces between punctures or spaces 1-2 times size of punctures); diameter of punctures equal to diameter of cells of microreticulation. Pronotum with much finer and sparser punctation than on head. Elytra with distinct punctation, slightly finer and sparser than on pronotum. Pronotum and elytra with weakly or more strongly impressed microreticulation; head with microreticulation stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles. Abdominal ventrites with strioles and very fine, sparse punctation.
Structures: Pronotum with 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 bead and few setae laterally. Abdominal ventrite 6 slightly truncate.
Male: Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of more than 60 and posterior band of ca. 30 relatively long setae, which connected approximately in middle (Fig. 33D). Abdominal ventrite 6 with 1-4 lateral strioles on each side. Median lobe with apical lobes very strongly developed, rounded in lateral view, "nose" small but distinct (Fig.  33A, B). Paramere as in Fig. 33C.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrites 5 and 6 without strioles.
Affinities. Exocellina pseudojaseminae sp. nov. can be distinguished by its size, dorsal colouration and punctation, shape and setation of its median lobe and paramere from the species of the E. danae group (E. nomax and E. pulchella sp. nov.) co-occurring in the same area. In its external appearance and shape of the median lobe, E. pseudojaseminae is very similar to E. jaseminae but it has more strongly developed apical lobes of the median lobe and much larger, hook-like anterolateral seta of the male protarsomere 4. For further affinities within the group, see the "Key".
Distribution. Papua New Guinea: Central Province (Fig. 34). Etymology. The species was mistaken for E. jaseminae due to their similarity in general appearance and shape of the median lobe. The name is a noun in the nominative singular standing in apposition.

Exocelina larsoni group
This group is characterised by fine and sparse dorsal punctation; pronotum with very narrow lateral bead; median lobe of aedeagus with or without setation, very broad, robust, with sides strongly thickened; in ventral view, almost parallel-sided, with slight median constriction; apexes of ventral sclerites of median lobe very unequal: right one much longer than left one; paramere slightly concave on dorsal side and with long and dense subdistal and inconspicuous proximal setae.
Type material studied. Paratypes: 2 males "PAPUA NEW GUINEA Baiteta March 13, 1991 D. J. Larson" (NHMW). Note: According to the original description (Balke 1998), the holotype is deposited in the collection of D. Larson and is in the Australian National Insect Collection now. The holotype was not studied since the species is very characteristic and two paratypes from the same locality were examined.
Affinities. In the area of its distribution, E. larsoni co-occurs with numerous species of the E. ekari, E. ullrichi, E. broschii, and E. danae groups. From all them, this characteristic species can be easily distinguished by its size, colouration, fine surface sculpture, simple male antennae, and mainly by the shape of the median lobe. Even females of the species differ from more similar in body form E. brahminensis Shaverdo et al., 2012 and E. broschii (Balke, 1998) in colouration (more uniform in two latter species) and narrow pronotal bead (absent E. brahminensis in and distinct in E. broschii). For affinities within the group, see the "Key".
Distribution. Papua New Guinea: Madang and Eastern Highlands Provinces. The species is known from numerous specimens from the central and wertern part of Madang and from northern part of Eastern Highlands (Fig. 45).
Colouration: Dark brown, with paler sides of pronotum and head. Head reddish to reddish brown, darker posterior to eyes. Pronotum brown to dark brown on disc and reddish to reddish brown on sides. Elytra uniformly dark brown. Head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 36). Teneral specimen paler.
Surface sculpture: Shiny dorsally, with inconspicuous punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 1-3 times size of punctures); diameter of punctures smaller than or equal to diameter of cells of microreticulation. Pronotum with finer and sparser punctation than on head. Punctation on elytra finer and sparser than on pronotum, inconspicuous, in some specimens invisible. Disc of pronotum and elytra with weakly impressed microreticulation; head and lateral sides of pronotum with microreticulation stronger.
Structures: Pronotum with narrow lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, narrow, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 truncate.
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Notes on identity of the additional material with the holotype, affinities. Balke (1998: 334) indicates Exocelina nomax as species minus cognitus. However, our study of the material collected from Tapini, village ca. 20 km north to Mafulu, allows us to consider with certain confidence that it belongs to E. nomax. It is the only Exocelina species collected from this area, and it was collected in abundant number (50 specimens) in Tapini. We assume this locality as the most northern distribution border of the species, which is very numerous in Kokoda and Kailaki areas. Morphologically, the specimens from Tapini, Kokoda, Kailaki and Varirata are identical to the holotype (Fig. 36A, B). Only three species occur close to Tapini-Mafulu area: E. garaina, E. posmani Shaverdo &Balke, 2016, andE. woitapensis Shaverdo &Balke, 2016 (the E. danae group). But they are larger (TL-H 3.6-4.5 mm), and the smallest of them, E. woitapensis, is matt dorsally. Moreover, E. nomax can be differentiated from them by its narrow pronotal bead, a very characteristic feature. Smaller size and narrow bead of the pronotum can be used to distinguish it from E. jaseminae, a species very similar to it in colour and surface structures. From the other species co-occurring in the Central and National Capital District Provinces (E. bacchusi, E. pulchella sp. nov., and species of the E. danae and E. jaseminae groups), E. nomax can be distinguished by its body size and colouration, dorsal punctation and microreticulation, narrow pronotal bead, and shape and setation of its median lobe and paramere. See also under E. warahulenensis sp. nov. and "Key".

Exocelina warahulenensis
Colouration: Piceous, with reddish sides of pronotum and head. Head reddish to reddish brown, darker posterior to eyes. Pronotum brown to piceous on disc and reddish to reddish brown on sides. Elytra dark brown to piceous. Head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 37). Teneral specimen paler.
Structures: Pronotum with narrow lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, relatively broad, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 truncate or slightly concave.
Median lobe slender, with lateral setae apically; in lateral view, evenly curved to broadly pointed, short apex; in ventral view, apex slightly concave (Fig. 42A, B). Paramere very slightly concave on dorsal side, with long and dense subdistal and inconspicuous proximal setae (Fig. 42C).
Female: Without evident differences in external morphology from males, except for not modified protarsi and abdominal ventrite 6 without striae.
Affinities. Exocellina warahulenensis sp. nov. can be distinguished by body size, form, colouration, inconspicuous dorsal punctation, simple male antenna, and shape and setation of its median lobe and paramere from the species co-occurring in the same area (E. damantiensis, E. hintelmannae, and E. ullrichi (Balke, 1998)). In the dorsal colouration and surface sculpture, the new species is similar to E. larsoni but differs from it in shape and presence of setation of the median lobe. Exocelina warahulenensis sp. nov. is also very similar to E. nomax but is slightly larger and has darker colouration and longer median lobe, with lateral setae apically and shorter, broader apex in lateral view.
Distribution. Papua New Guinea: Simbu and Eastern Highlands Provinces (Fig.  45). The species is known only from Crater Mountain area.
Etymology. The species is named after Wara Hulene Village where one of the paratype was collected. The name is an adjective in the nominative singular.

Exocelina takime group
This group is characterised by more or less coarse and dense dorsal punctation; pronotum with narrow lateral bead; median lobe of aedeagus without setation, broad, robust, sides slightly thickened; in ventral view, it broadened medially or subdistally; apexes of ventral sclerites of median lobe almost equal; paramere with distinct dorsal notch and subdistal part well developed, with long and dense subdistal and inconspicuous proximal setae. Colouration: Piceuos. Head piceous, with reddish brown anterior margin. Pronotum dark brown to piceous, with reddish brown to brown sides. Elytra uniformly piceous. Head appendages and legs proximally yellowish, legs distally darker, reddish brown (Fig. 38). Teneral specimen paler.

Exocelina mianminensis
Surface sculpture: Submatt dorsally, with dense and coarse punctation and weakly impressed microreticulation. Head with very dense and coarse punctation (no spaces between punctures or spaces 1-2 times size of punctures); diameter of punctures equal to diameter of cells of microreticulation. Pronotum with distinct punctation, finer than on head. Punctation on elytra distinct, finer and sparser than on head. Elytra with weakly impressed microreticulation; head and pronotum with microreticulation stronger than on elytra. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites 2-4 with few strioles, two last one without strioles but with very weak wrinkles. Punctation on venter fine but distinct.
Structures: Pronotum with narrow lateral bead. Base of prosternum and neck of prosternal process with distinct ridge, rounded anteriorly. Blade of prosternal process lanceolate, narrow, slightly convex, with distinct bead and few setae laterally. Abdominal ventrite 6 truncate or very slightly concave.
Male: Protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of ca. 60 and posterior row of 17 relatively long setae (Fig. 43D). Abdominal ventrite 6 without lateral striae on each side, except one with setae. Median lobe slender, lateral sides slightly thickened; in lateral view, apex short, pointed, and curved downwards; in ventral view, lateral sides evenly expanded subdistally and apex slightly concave (Fig. 43A, B). Paramere with distinct dorsal notch and subdistal part well developed, with long and dense subdistal and inconspicuous proximal setae (Fig. 43C).
Female: Without evident differences in external morphology from males, except for not modified protarsi.
Affinities. In the area of its distribution, E. mianminensis co-occurs with species of the E. ekari, E. okbapensis, E. broschii, E. casuarina and E. danae groups. From species of the E. ekari group, the species differs in larger size, presence of the pronotal bead, evidently stronger dorsal punctation, and the shape of the median lobe. From the other species, E. mianminensis sp. nov. can be distinguished by body size, form, and colouration, dorsal punctation, simple male antenna, and shape and setation of its median lobe and paramere. In the general appearance, the new species is more similar to E. ibalimi Shaverdo et al., 2018, but can be easily distinguished from it in presence of the pronotal bead. Male abdominal ventrite 6 without lateral striae was so far known only for E. sima Shaverdo et al., 2018 among New Guinea Exocelina. For affinities within the group, see the "Key".
Distribution. Papua New Guinea: Sandaun Province (Fig. 45). Etymology. The species is named after Mianmin Village. The name is an adjective in the nominative singular.
Diagnosis. For complete description, see Balke (1998: 336). Beetle medium-sized: TL-H 4.1-4.5 mm; oblong-oval; dark brown to piceous, with brownish pronotal sides and head anteriorly; shiny, but with distinct dorsal punctation and weakly impressed microreticulation; pronotum with narrow lateral bead (Fig. 39); male protarsomere 4 with large, thick, strongly curved anterolateral hook-like seta; male protarsomere 5 with anterior band of ca. 40 and posterior row of eight relatively long setae (Fig. 44D); median lobe robust, in lateral view, evenly curved to narrowly rounded, not curved downwards apex; in ventral view, with more strongly thickened lateral sides, distinctly expanded in middle and narrowing to broadly pointed apex; paramere with distinct dorsal notch and subdistal part well developed, with long and dense subdistal and inconspicuous proximal setae ( Fig. 44A-C).
Affinities. In the area of its distribution, E. takime co-occurs with E. aipomek, E. ascendens and species of the E. bacchusi, E. ekari, E. aipo, E. okbapensis, E. casuarina, and E. danae groups. From species of the E. ekari group, the species differs in larger size, evidently stronger dorsal punctation, and the shape of the median lobe. In the latter character, E. takime differs also from the species of the remaining groups. For separating it from some of these species, also presence of the pronotal bead and simple male antennae, and shape and setation of the paramere can be used. For affinities within the group, see the "Key".

1
Beetle smaller, TL-H 3.75-4.25 mm. Dorsal punctation coarser (Fig. 38). Median lobe slender, with lateral sides slightly thickened; in ventral view, evenly expanded subdistally, apex slightly concave; in lateral view, apex short, pointed, and curved downwards (Fig. 43). Paramere as in Fig. 43C (Fig. 39). Median lobe with strongly thickened lateral sides; in ventral view, distinctly expanded in middle and narrowing to broadly pointed apex; in lateral view, evenly curved to narrowly rounded, not curved downwards apex (Fig. 44). Paramere as in Fig. 44C (Balke, 1998) A median lobe in ventral view B median lobe in lateral view C paramere in external view D male protarsomeres 4-5 in ventral view.

Exocelina warasera group
This group is characterised by extremely fine and sparse dorsal punctation; pronotum with distinct lateral bead; median lobe of aedeagus simple; in lateral view, slightly or more strongly curved, apex slightly curved downwards and bluntly pointed; in ventral view, apex bluntly pointed and often twisted sidewards; apexes of ventral sclerites of median lobe almost equal; paramere slightly concave on dorsal side, subdistal setae strong and dense, proximal setae usually inconspicuous.  Description. Body size and form: Beetle small: TL-H 3.4-3.45 mm, TL 3.7-3.75 mm, MW 1.8 mm (holotype: TL-H 3.4 mm, TL 3.7 mm, MW 1.8 mm), with oblong-oval habitus.
Surface sculpture: Shiny dorsally, with extremely fine and sparse punctation and weakly impressed microreticulation. As in E. warasera sp. nov.
Structures: Pronotum with 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 bead and few setae laterally. Abdominal ventrite 6 very slightly concave.
Male: Protarsomere 4 with anterolateral seta thin and evenly curved, smaller than more laterally situated large seta. Protarsomere 5 ventrally with anterior band of ca. 80 and posterior row of two relatively long setae (Fig. 53D). Abdominal ventrite 6 with 6-8 lateral striae on each side. Median lobe short, curved, with broadly pointed apex in lateral view, and evenly tapering to pointed apex in ventral view (Fig. 53A, B). Paramere concave on dorsal side, with dorsal setae distinct: subdistal setae only slightly stronger and denser than proximal (Fig. 53C).
Distribution. Papua New Guinea: Simbu Province, Crater Mountain area (Fig.  54). The species is named after Haia Village. The name is a noun in the nominative singular standing in apposition. Colouration: Piceous, with paler sides of pronotum and head anteriorly. Head dark brown, paler anteriorly. Pronotum dark brown, with brown sides. Elytra piceous, with weakly indicated reddish sutural lines. Head appendages and legs proximally reddish, legs distally darker, reddish brown (Fig. 46).

Exocelina kobau
Surface sculpture: Shiny dorsally, with extremely fine and sparse punctation and weakly impressed microreticulation. Head with fine and sparse punctation (spaces between punctures 2-3 times size of punctures); diameter of punctures equal to or smaller than diameter of cells of microreticulation. Pronotum with much finer and sparser punctation than on head, very inconspicuous. Punctation on elytra invisible. Pronotum and elytra with weakly impressed microreticulation; head with microreticulation slightly stronger. Metaventrite, metacoxae, and abdominal ventrites distinctly microreticulate. Metacoxal plates with longitudinal strioles and weak transverse wrinkles; abdominal ventrites with strioles. Punctation on venter invisible; inconspicuous on two last abdominal ventrites.
Structures: Pronotum with 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 bead and few setae laterally. Abdominal ventrite 6 truncate.
Female: Unknown. Affinities. Exocellina kobau sp. nov. can be distinguished by its size, dorsal punctation, shape and setation of its median lobe and paramere, and large anterolateral hook-like seta of the male protarsomere 4 from the species co-occurring in the same area (E. damantiensis, E. kabwumensis Shaverdo & Balke, 2016, and E. bacchusi). For the affinities within the group, see the "Key".
Distribution. Papua New Guinea: Morobe Province (Fig. 54). Etymology. The species is named after Kobau Village. The name is a noun in the nominative singular standing in apposition.   Beetle colourful, with reddish head and bicoloured elytra: yellowish at shoulders and brownish distally; smaller, TL-H 2.85-3.3 mm (Fig. 47)  Apex of median lobe shorter and thicker, with right lateral margin slightly concave (Fig. 52)  EHP, Papua New Guinea, as well as the PNG Binatang Research Center, Madang, Papua New Guinea. Thanks are especially due to our PNG friends Vojtech Novotny, Aloysius Posman, Bangan John, Andrew Kinibel, and Sentiko Ibalim, whose help is greatly appreciated. The specimens from Mount Wilhelm, Papua New Guinea were collected during the "Our Planet Reviewed Papua-New-Guinea 2012-2013" project. Sorting and processing of the material was supported by the European Research Council (ERC) grant 669609 to C. Wardhaugh. We express our gratitude to our Indonesian friend Bob Sumoked, naturalist, explorer, nature lover, and mountaineer for looking for beetles once the campfire was burning and the tents were set up. Never stop exploring! We thank Museum Zoologicum Bogoriense, Cibinong, Indonesia for hosting the type material and lending selected specimens for imaging, especially to Dr D. Peggie and Pak Sarino. Specimens were exported with permission from the Department of Environment and Conservation (DEC, Port Moresby), or loaned from MZB/KSP in the framework of a formally established longer-term capacity building program between the Cenderawasih University (Waena, Papua) and SNSB-ZSM (Munich).