Biogeographical and evolutionary aspects of a Guineo-Congolian bushcricket tribe: Revision of the genera Cestromoecha Karsch, 1893 and Poreuomena Brunner von Wattenwyl, 1878, with the description of new species (Orthoptera, Tettigoniidae, Phaneropterinae)

The genera Cestromoecha and Poreuomena of the tribe Poreuomenini in Phaneropterinae are revised and new generic characters are given for both genera, and six new species are described in Poreuomena. The newly described species are P. biaculeata sp. nov., P. eala sp. nov., P. gracilicercata sp. nov., P. ivoriana sp. nov., P. matthaei sp. nov., and P. tshuapa sp. nov. Based on characters defining the two genera, three species so far listed under Cestromoecha are transferred to Poreuomena: P. crassipes Karsch, 1890, P. laeglae (Massa, 2015), and P. magnicerca (Massa, 2013). One species of Cestromoecha, C. mundamensis Karsch, 1896, is synonymised with C. tenuipes (Karsch, 1890) since no morphological differences were detected between the type specimens. Thus, two species remain with Cestromoecha, and Poreuomena now contains 16 species. Morphological closely-related species of Poreuomena suggest rapid speciation in the Congo Basin due to several expansions and shrinkages of the Guineo-Congolian forest belt since the Oligocene. At least two different morphological lineages are discernible. On the other hand the genus Cestromoecha Karsch, 1893 is a species-poor taxon.


Introduction
Information on Phaneropterinae and also other Orthoptera of Central to West Africa is sparse. Most research activity, mainly the collecting of specimens, reaches back to colonial times. More recent studies in parts of Africa were conducted by, for example, Naskrecki (2009) or Heller et al. (2014). Only recently further more comprehensive research was conducted in West (Côte d'Ivoire) and Central Africa (Central African Republic) including light trapping, thus enabling the study of the Tettigoniidae fauna of these areas in more detail (e.g. Massa 2013Massa , 2015Massa , 2016Massa , 2017Massa , 2018Massa , 2020Hemp and Massa 2017;Massa et al. 2020). New species of Poreuomena have been detected by visiting various entomological collections in Europe or within material received from African expeditions.
In this study, we focus on the tribe Poreuomenini which includes the three genera, Cestromoecha Karsch, 1893, Poreuomena Brunner von Wattenwyl, 1878and the monotypic Paraporeuomena Massa, 2018, tentatively included in the tribe. Currently, the genera Cestromoecha and Poreuomena contain 13 species, all from central-western Africa. We review the genera Poreuomena and Cestromoecha providing new characters on generic level since both genera were described only on the few male specimens present at that time only by Brunner von Wattenwyl (1878) and Karsch (1893). A biogeographical analysis is conducted on the basis of the morphology of the outer male genitalic apparatus.

Materials and methods
Most specimens studied in the present paper were studied in museum collections, others were collected at nighttime attracted to light (UV) both on the ground and in the canopy of central-western countries of tropical Africa during scientific expeditions. Before mounting specimens, the left wing of every male having different cerci was spread in order to allow the study of the stridulatory file on the underside of the left forewing; the number and arrangement of the teeth are diagnostic and are useful characters to identify whether a species is bioacoustically separated from one another (Heller 2006). Characters of specimens, such as stridulatory area, stridulatory file, cerci in frontal and lateral views were photographed with a Nikon Coolpix 4500 digital camera, mounted on a Wild M3 Stereomicroscope, or with an Olympus Tough F2.0 camera. Photographs were integrated using the freeware CombineZP (Hadley 2008). Mounted specimens were measured with a digital caliper (precision 0.01 mm). Due to the difficulties in identifying females, in the present paper, they are included only in case they were collected at the same locality and on the same date as a corresponding male.

Tribe Poreuomenini Brunner von Wattenwyl, 1878
Iconography. The name Poreuomena is probably derived from the Greek verb Πορεύω meaning "bringing something into a definite direction". The name Cestromoecha is probably derived from Κέστρον, an instrument used in pyrography (drawing by means of heat), pointed on one side and rounded on the other. The same name was used by the Macedonians to indicate a particular type of arrow; the word indicates something that has the form of κέστρον (κέστρον μοι έχειν).
Remarks on the tribe Poreuomenini. Brunner von Wattenwyl (1878) erected the group Poreuomenae and the genus on the single species Poreuomena africana from Gabon, the only species known in this group at that time. Brunner von Wattenwyl (1878) noted that the new genus is similar in habitus to the genus Phaneroptera. Regarding differences to Phaneroptera both sides of the tympanal organs are closed in Poreuomena (not true for all newly-described species though, see below) while they are open in Phaneroptera. Furthermore, the fore tibiae are smooth without any furrow at their dorsal sides and completely unarmed. These characters differentiate the Poreuomenini from Phaneropterini and place them near to the Holochlorini (formerly divided into Holochlorae and Psyrae). Since Poreuomena was erected on the species africana generic characters were the 10 th abdominal tergite of the males being extended in two lobes and the Rs vein branching off near the base of the tegmen. Karsch (1890) described Poreuomena tenuipes but erected a few years later his own genus on this species (Karsch 1896). The differentiating character for the two genera as given by Karsch (1896) was a bilobed 10 th male tergite in Poreuomena and an undifferentiated 10 th tergite in Cestromoecha. Further Karsch noted that the first side vein of the radius (Rs) typically branches off near the base in Poreuomena but more in or behind the middle in Cestromoecha (Figs 1, 2). Comparing all species we found that a further typical character of Poreuomena is flaps on both tegmina -both with stridulatory files on the underside (Figs 6-8). A flap and very likely convergentlyevolved similar structure is only found in the East African endemic Ectomoptera Ragge, 1980 that has, however, a well-developed mirror on the right tegmen, while in Poreuomena a mirror is lacking completely. On the right tegmen only a reduced stridulatory file is found in Ectomoptera (for a review of stridulatory files on the right tegmen of Ensifera see Leroy 1970or Chamorro-Rengifo et al. 2014. Table 1 shows a compilation of characters for species of the two genera Poreuomena and Cestromoecha with respective taxonomic changes. Referring to the type species of Poreuomena, P. africana, and Cestromoecha, C. tenuipes, several species are currently misplaced and are here transferred to their respective genus on grounds of generic characters given above and below. A very obvious distinguishing character on generic level is the presence (Poreuomena africana) or Mirror area of Cestromoecha tenuipes lacking the flaps on both tegmina bases, but with a well-developed mirror on the right tegmen (arrows). 5. Mirror area of Cestromoecha tenuipes from the underside with a well-developed stridulatory file, typical for all Poreuomenini.  Table 1. Morphological characters of the genera Poreuomena and Cestromoecha. Rs: Position of Rs branching off from radius. Flaps: flaps on both tegmina developed or not. Mirror: mirror on right tegmen developed or not. 10 th : 10 th abdominal tergite "bilobed" (derived from the basic structure of an elongated 10 th tergite with lateral bulges or short or long, straight or downcurved lateral processes) or undifferentiated or differently shaped.

Species
Rs Flaps Mirror 10 th abdominal tergite Cestromoecha C. longicerca Massa, 2013 behind middle no large mirror stout 10 th tergite with almost straight posterior margin C. mundamensis Karsch, 1896 (synonym with the following species) behind middle no small mirror straight margin with median ridge C. tenuipes (Karsch, 1890) behind middle no small mirror undifferentiated, straight margin Poreuomena P. africana B. v. Wattenwyyl, 1878 basal yes no bilobed: posteriorly produced with two thick downcurved processes P. biaculeata sp. nov. basal yes no bilobed: posteriorly produced with two laterally compressed downcurved lobes P. crassipes (Karsch, 1890) stat. nov. basal yes no bilobed; elongated downcurved flap forming two bulges P. duponti Griffini, 1908 basal yes no bilobed : posteriorly produced with two thick processes P. eala sp. nov. basal yes no bilobed: posteriorly produced with two bulgy lobes P. forcipata Sjöstedt, 1902 basal yes no bilobed: posteriorly produced with two thick somewhat laterally expanded and downcurved processes P. gracilicercata sp. nov. basal yes no bilobed: two stout bulges with long downcurved processes P. huxleyi Massa, 2013 basal yes no bilobed: posteriorly produced with short stout processes narrowing suddenly to a thin elongate, laterally compressed, flagellum-like shape P. laeglae (Massa, 2015) stat. nov. basal yes no two broad but narrow lobes with median gap P. lamottei Chopard, 1954 basal yes no bilobed: posteriorly produced with two stout and downcurved lateral processes P. magnicerca (Massa, 2013) stat. nov. basal yes no undifferentiated, straight margin P. matthaei sp. nov. basal bulge no broad, shield-like with median gap P. sanghensis Massa, 2013 basal yes no bilobed: broad with short lateral flanges forming a u-shaped gap between them P. tshuapa sp. nov. basal yes no broad with shallow median depression and two reduced knob-like processes P. wilverthi Griffini, 1908 basal yes no bilobed: broad with short lateral flanges absence (Cestromoecha tenuipes) of a mirror on the right side of the tegmen (Figs 3-5) -as well as the well-developed flaps with the stridulatory files on the underside in Poreuomena (Figs 6-8). Cestromoecha either has, at most, a small bulge on the left tegmen and a separate flap with a stridulatory file on the underside on the right wing but a well-developed mirror. Karsch (1896) noted that he could not decide whether Poreuomena crassipes, described by him on a single female, also belonged to the new genus Cestromoecha or not since the male was unknown. Ragge (1968) in his index-catalogue of African Phaneropterinae listed the latter species under Cestromoecha without giving reasons for this change. Massa (2013) described the male of C. crassipes leaving it with Cestromoecha, although having a bilobed 10 th tergite and tegminal flaps typical for Poreuomena. Poreuomena magnicerca transferred by us from Cestromoecha, has typical tegminal flaps, a Rs branching off from the radius near the base of the tegmen, however, for Poreuomena, with an untypical, undifferentiated and thus not bilobed 10 th abdominal tergite. All other known Poreuomena species, including the here newly-described species have tegminal flaps on both tegmina, except for P. matthaei sp. nov. with a bulge at the right base of the tegmen. A flap is here defined as elongated and narrow, mostly pointed structure at the base of the tegmina, while a bulge is a broad and not pointed structure. Further, Poreuomena species have a Rs branching off from the radius near the base and a 10 th abdominal tergite derived from a bilobed basic structure (elongated bulges or with short or long, straight or downcurved lateral processes). Two species remain in Cestromoecha, C. tenuipes (syn. C. mundamensis) and C. longicerca, both having mirrors on the right side of the tegmen and no tegminal flaps (Figs 10,12,17).
Genus Cestromoecha Karsch, 1893 Figs 9-21 Cestromoecha Karsch, 1893. Berlin Ent. Z. 38: 128; type species: Poreuomena tenuipes Karsch, 1890 Re-description. Medium-sized, predominantly green, typical Phaneropterinae with narrow and elongate tegmina surpassed at their apices by the alae. Fastigium verticis smaller than the width of the scapus; triangular with rounded apex, shallowly sulcate, separated from conical fastigium frontis by a gap. Antennal sockets elevated beside fastigia. Fore coxa with a spine. Fore and mid femora dorsally rounded, ventrally with very tiny spinules. Hind femora slender, slightly thickened in basal part, with few tiny spinules along the ventral length. Fore tibiae very slender, thickened in the area of the tympana and slightly sulcate dorsally; tympana open on the inner, conchate on the outer side. Hind tibiae triangular or narrow rectangular in diameter, densely packed along each edge with slender spines; dorsally with a pair of tiny spurs on each side, ventrally with each one larger spur on each side.
Left tegmen of typical Phaneropterine shape, with a slight bulge where the stridulatory file is located at the underside (Figs 10,17). The right tegmen with a well-developed mirror (Figs 3,5). Male 10 th abdominal tergite either flap-like or stout (Figs 13,14,20). Cerci from stout to long, slender and pointed; subgenital plate deeply bilobate; without styli (Figs 15,21).  (9). Stridulatory area with mirror on right tegmen (10), stridulatory file on the underside of the left tegmen (11), close-up of mirror (12), abdominal apex in lateral view (13), rear view (14) and subgenital plate (15).  11-12. II. 2012, 21-22. II. 2012 Diagnosis. Sjöstedt (1912) stated that Griffini (1905/6) found no differences between C. tenuipes and C. mundamensis, both described by Karsch. Sjöstedt mentions that a generic character on which Cestromoecha was erected, is a missing mirror on the right tegmen, while C. mundamensis has a well-developed mirror. However, both C. tenuipes (Fig. 17) and C. mundamensis males have well-developed mirrors and a comparison of the outer genitalic system of both C. tenuipes  and C. mundamensis showed no differences. Therefore, we suggest to synonymize both species that also have an overlapping distribution pattern to be synonymised.
Distribution. Central to West Africa. Re-description. Medium-sized, predominantly green typical Phaneropterinae with narrow and elongate tegmina surpassed at their apices by the alae. Fastigium verticis smaller than the width of the scapus; triangular and sulcate above, separated from the conical fastigium frontis by a gap. Antennal sockets elevated beside fastigia. Fore coxa with a spine. Fore and mid femora dorsally rounded, ventrally with very tiny spinules. Hind femora slender, slightly thickened in basal part, with few tiny spinules along the ventral length. Fore tibiae very slender, thickened in the area of the tympana and sulcate dorsally; tympana open on inner, conchate on outer side. Hind tibiae triangular or narrow rectangular in diameter, densely packed along each edge with slender spines; dorsally with a pair of tiny spurs on each side, ventrally with one larger spur on each side. Bases of the tegmina differentiated into flaps; on each of these flaps, a similar shaped stridulatory file on the underside is present. No mirror developed on the right tegmen. Rs vein branching off from the radius basally. Male 10 th abdominal tergite usually bilobate, either with evenly rounded lobes, lobes reduced to short bulges or strongly elongated. Male cerci simple, expanded at their tips or differentiated in differently-shaped branches. Subgenital plate elongated (but not markedly surpassing abdominal apex) with mostly a pair of short stout to more slender lobes or unlobed with two rounded apices at the posterior margin. All checked specimens also have an area of dark cells surrounded by the green more elevated veins in the cubital area of the tegmina. Diagnosis. The 10 th abdominal tergite (Fig. 25) is similar to that of P. lamottei (Fig. 78) -with two lateral processes. However, the male cerci are completely different in P. africana, broader at the base tapering to acute tips of the two branches (Figs 22,25,28) while the male cerci in P. lamottei are simple, expanded into three tips apically (Fig. 78).
Colour. Small species, uniformly green-yellowish, a little brownish around the stridulatory area ( Fig. 23) and small black dots on the posterior margins of the tegmina.
Measurements (mm). Males. Body length: 18.5-19.9. Pronotum length: 3.7-3.8. Pronotum height: 2.8-2.9. Length of hind femora: 19.6-19.8. Length of tegmina: 26.5-26.8. Width of tegmina: 4.5-4.6. Diagnosis. Very closely related to P. wilverthi, a species widespread in the Congo basin and the Albertine Rift. P. biaculeata sp. nov. has the 10 th abdominal tergite deeply split into two lobes (Figs 33,34), while in P. wilverthi the 10 th abdominal tergite is not divided as deeply, just at the apex however, with a median groove. The cerci in P. wilverthi are thick but smoothly tapering to the apex with an acute tip (Figs 105, 106), while in P. biaculeata sp. nov., the cerci are thick at the base and then suddenly narrowing midway forming a finger-like but pointed and sclerotized apical section (Figs 32-34). P. biaculeata sp. nov. is also closely related to P. crassipes with a similar tegminal flap of the 10 th abdominal tergite but differently shaped cerci.
Description. Male. Typical Poreuomena species with wings protruding over the body by only a few mm (Fig. 29). Where tegmina meet, when folded, interior part of cells of dark colour while surrounding and elevated veins green (tawny in preserved insect). Rs branching off in the first half of the basal part of the tegmen. Tegmina with two flaps at their base, the flap of the left wing smaller and more pointed than the broader flap with a rounded tip on the right tegmen. The stridulatory rib marked dark brown on the flap of the left tegmen, uniformly brown on the right tegmen. Beneath flaps, tegmina with narrow longish, oval brown markings. Stridulatory file on the underside of left flap about 1.1 mm long; teeth at the apical part of the left flap very densely set and gradually getting larger to the middle of the file where the teeth are largest and widely set. At the end of the file at the interior part, strongly curved with small and a few widely set teeth; with about 20 widely and in the middle large teeth, apically more than 30 very densely set teeth (Fig. 31). Stridulatory file on the right tegminal flap not as strongly developed but of similar shape and the same arrangement of the teeth. The 10 th abdominal tergite of typical bilobate form, deeply divided medially thus forming two processes with upcurved posterior parts (Figs 33,34). Cerci thick at the base, then strongly narrowing and forming a sclerotised pointed apical tip (Figs 33,34). Subgenital plate with two slender but short lobes (Fig. 35). Titillators present (two slender long structures), protruding between the subgenital plate and the cerci (Fig. 32).
Distribution. Congo Basin. Etymology. Named after the shape of cerci that are similar to two stings, from Latin biaculeatus (= with two stings). Diagnosis. Morphologically closely related to P. biaculeata sp. nov. and P. wilverthi. All three species share a similar 10 th abdominal tergite that is flap-like, deeply divided into two lobes in P. biaculeata sp. nov. (Figs 33,34), with an indentation only at its posterior margin and a central furrow in P. wilverthi (Fig. 107) and with only a shallow groove medially in P. crassipes (Fig. 40). The cerci of the three species are also similar, stout at their bases, narrowed halfway into a sclerotised tip in P. biaculeata sp. nov. (Figs 33,34), evenly tapering into a tiny sclerotised tip in P. wilverthi (Figs 104,106) and stout in P. crassipes with two sclerotised dents at their apices (Figs 39,40).

Diagnosis.
Rather stout species with a 10 th abdominal tergite differentiated into two bulges (Figs 48,49). The cerci are stout and upcurved with stout bifurcate tips (Figs 48,49). No other Poreuomena species has such a combination of bifurcate tips of the cerci and a 10 th abdominal tergite differentiated into two bulges.
Description. Male. Stout species with wings projecting over the body by about half of their length. Where tegmina meet, when folded, interior part of cells of dark colour while surrounding and elevated veins green. Rs branching off in the first half of the basal part of the tegmen. Tegmina with two flaps at their base, the flap of the left wing smaller and more pointed than the broader flap with a rounded tip on the right tegmen. The stridulatory rib marked dark brown on the flap of the left tegmen, uniformly brown on the right tegmen. Beneath flaps, tegmina with narrow longish brown markings. Stridulatory file on the underside of the left flap about 1.3 mm long; teeth at apical part of the left flap very densely set and gradually getting larger, about from half of the file teeth large and more widely to very widely spaced; inner part then strongly curved and teeth becoming smaller and then obsolete; with about 45-50 teeth (Fig. 50). Stridulatory file on the right tegminal flap not as strongly de-veloped, but of similar shape and the same arrangement of the teeth. The 10 th abdominal tergite bilobate, differentiated into two bulges (Fig. 48). Cerci stout along whole length, at their ends upcurved and divided into two tips (Figs 48,49). Subgenital plate elongated, deeply divided into two lobes; without styli ( Fig. 49). Between subgenital plate and cerci, two longish internal structures present (titillators) (Fig. 51).
Female. As male comparatively stout, of uniform green colour without brown markings (Fig. 45) present in males on and beneath the stridulatory area. As in the male, where tegmina meet when folded, interior part of cells of dark colour while surrounding veins green. Posterior margin of 10 th abdominal tergite differentiated into two lobes or bulges, similar to those of the male, but much smaller and shorter (Fig. 46). Ovipositor short and upcurved. Subgenital plate triangular with an indentation at the posterior tip (Fig. 47).
Distribution. DRC, Équateur Province. Etymology. Named after the area Eala where specimens of this species were collected.
Diagnosis. Griffini (1908) supposed that, because Bolívar (1906) overlooked the paper of Sjöstedt (1902), P. gladiator Bolívar, 1906 from Cameroon could be synonymous with P. forcipata Sjöstedt, 1902, also from Cameroon. The male cerci of the two taxa are identical. Both lack the black marking on the stridulatory area of the male left tegmen (Fig. 54); thus P. gladiator has been synonymised with P. forcipata by Massa (2013). Morphologically most closely related to P. laeglae (both species share an asymmetrical supra-anal plate with a spine on the left margin, Fig. 55), P. tshuapa sp. nov. and P. magnicerca (also see diagnosis at P. laeglae).
Description. Rather stout species with comparatively broad tegmina (Fig. 54). The 10 th abdominal tergite is broad with two lateral processes, while the cerci are highly modified into two branches (Figs 55, 56). The inner branch is blade-like with sclerotised margins, while the outer or apical one is finger-like (also see at P. tshuapa sp. nov.). This species has an asymmetrical supra-anal plate with a stout spine on the left side, lacking on the right ; Fig. 55 arrow). The male subgenital plate is triangular and has a small apical concavity (Fig. 56). The stridulatory file has ca. 35 teeth, the last 8-10 placed more or less perpendicularly to the main file (Fig. 53).
Distribution. Cameroon and the Central African Republic. Diagnosis. The elongated and slender shape of the male cerci -thickened in the middle with an inner dent -and the 10 th abdominal tergite forming two long downcurved processes are unique.
Description. Male. Typical Poreuomena species with wings protruding over the body by only a few mm. Where tegmina meet when folded, interior part of cells of dark colour while surrounding and elevated veins green (or tawny in preserved insect). Rs branching off in the first half of the basal part of the tegmen. Tegmina with two flaps at their bases, the flap of the left wing smaller and more pointed than the broader flap with a rounded tip on the right tegmen. Left flap completely marked brown, right one partly brown, especially along the bulge of the stridulatory file on the underside (Fig. 57). Beneath flaps, tegmina with narrow longish, dark brown markings. Stridulatory file on the underside of left flap about 1.2 mm long; upcurved at the inner end with few smaller and widely-spaced teeth (about 5), in the middle part with widely set large teeth (about 12) and, at the apical end, with densely-set teeth decreasing in size (about 10-12); distal end strongly curved downwards (Fig. 58). Stridulatory file on the right tegminal flap not as strongly developed, but of similar shape and the same arrangement of the teeth. The 10 th abdominal tergite forming at the anterior part two convex bulges, at its posterior end differentiated into two long and slender and downcurved processes (Figs 60, 61). Cerci strongly elongated, in the middle thickened with an inner sclerotised dent. Subgenital plate bilobate (Fig. 59).
Distribution. Democratic Republic of the Congo. Etymology. Named after the long and slender male cerci. Diagnosis. This species is easy to recognise by the short apical lobes on the 10 th tergite of the male and cerci clearly upcurved and with a lateral spine. The most closely-related species is P. africana, which, however, has much longer lobes of the 10 th abdominal tergite and more robust cerci. Description. Typical Poreuomena species with narrow tegmina surpassed by the alae by a few mm (Fig. 62). Stridulatory area marked brown (Fig. 64). Two spines are present on the ventral margin of the hind femora. The apical lobes of the 10 th tergite are short and square, separated widely (Fig. 63); the cerci are in-and downcurved, dorso-ventrally flattened in the apical portion where a lateral spine is present.

Poreuomena huxleyi Massa, 2013
Colour. P. huxleyi is brownish coloured, with green tegmina and hind tibiae; a black marking is typical at the base of the tegmina and some small black spots on the posterior margin of the tegmina.
Distribution. Equatorial Guinea and Cameroon. Diagnosis. P. ivoriana sp. nov. is a comparatively small species of Poreuomena, characterised by its green colour, the blackish triangular areas on the left and right tegmina (Fig. 65) and incurved cerci with a flattened inner process (Figs 67, 68). Probably morphologically related to P. lamottei distributed further west in Africa. The male cerci of both species are differentiated into flattened structures in both species, however, more pronounced in P. ivoriana sp. nov. The 10 th abdominal tergite is very different in both species. While in males of P. lamottei, the posterior margin of the 10 th abdominal tergite forms two comparatively long and, at their tips, downcurved processes, in P. ivoriana sp. nov. only two short lobes are developed.
Description. Male. Green coloured with a faint blackish stripe on the stridulatory area; the triangular area close to the stridulatory file above the left tegmen and the corresponding area on the right tegmen are black. Antennae thin, fastigium of the vertex separated from the fastigium of the frons, face smooth, eyes round, prominent. Pronotum with a flat and smooth disc, the anterior margin straight, the posterior margin broadly rounded. Tegmina narrow, ca. 5.8 times broader than long, stridulatory area of the left tegmen short. The flap of the left tegmen comparatively broad (damaged in the holotype) (Fig. 65). The corresponding flap on the right tegmen also broad. Stridulatory file 0.3 mm long, with ca. 45 little arched teeth which are more evenly spaced at their base than at the apex (Fig. 66). Fore coxa armed with a small spine, fore femora with 4 small spines on ventral inner margins, mid femora with 4-5 small spines on ventral outer margins, hind femora with 2-3 rows of small ventral spines distally. Fore tibiae with tympa- num conchate on inner and open on the outer side, with 2-3 small spines on inner margins, mid tibiae with 9-10 small spines on outer and inner margins, hind tibiae with numerous spines and 3 apical spurs on each side. Last abdominal tergite flattened and enlarged with two apical small pointed processes, cerci stout, short and incurved, before their tips, they have an inner flattened process (Figs 67-69). Subgenital plate long with a narrow concavity and two parallel pointed processes; styli absent ( Fig. 69).
Measurements (   Diagnosis. P. laeglae was described in the genus Cestromoecha, but it actually belongs to the genus Poreuomena because it has two well-developed tegminal flaps and no mirror. The Rs vein branches off near the base and not past the middle as typical for Cestromoecha. It is morphologically most closely related to P. forcipata (both species share an asymmetrical supra-anal plate with a spine on the left side) and also to P. magnicerca and P. tshuapa sp. nov. The cerci of the males are differentiated into two branches in the first two species, with a finger-like apical or outer branch and a blade-like expanded inner branch, however, differently shaped between P. laeglae and P. forcipata. In P. magnicerca and P. tshuapa sp. nov., the third blade-like branch or expansion is present giving the expression of the cerci having three branches. The flaps on the left tegmina bearing the stridulatory files on the underside are differently shaped between P. tshuapa sp. nov. (oval and pointed) and P. magnicerca (laterally slightly expanded and not pointed) as is the shape of the stridulatory file itself supporting species status for P. tshuapa sp. nov. The 10 th abdominal tergites, however, are very similar amongst these four species since they are rather undifferentiated with a more or less straight posterior margin and thus very likely derived from the bilobed condition as the generic character of the genus Poreuomena.
The stridulatory file of P. laeglae is similar to that of P. magnicerca with a distal part with less and more widely-spaced teeth than in the proximal part (Massa 2015).
Description. Typical Poreuomena species with elongated habitus. Fore and mid femora with 4-5 very small spines, fore tibiae with 3 ventral spines + 1 spur on each side, mid tibiae with 6-7 ventral spines + 1 spur on each side, hind tibiae with 3 spurs on each side. Ventral margins of hind femora with 2 small basal spines. Tegmina narrow, stridulatory area of left tegmen black and straight; stridulatory file downcurved with ca. 50 teeth, distal part with asymmetrical and widely-spaced teeth (Fig. 71). The 10 th tergite slightly bilobate with an asymmetrical supra-anal plate having a spine on the left side at the margin (Fig. 72, arrow) (similar to P. forcipata, Fig. 55, arrow). Cerci stout, long and incurved, with the basal part rounded and the apical part flattened and pointed (Fig. 72); in the middle, with a well-developed flattened large inner spine, blackish at the tips (Fig. 73). Subgenital plate concave, triangular and long, with a deep concavity, processes almost parallel (Fig. 74).
Colour. Probably predominantly green when alive, brown to tawny when preserved. Stridulatory area of left tegmen and area below black. Small black spots are present on the posterior margins of the tegmina. Two longitudinal parallel dark lines are present on the outer surface of the hind femora.
Measurements ( Diagnosis. P. lamottei has a similar 10 th abdominal tergite as P. eala sp. nov., but the lobes are much narrower and have a large gap between them in P. lamottei. In addition, the male cerci are similar between the two species, stout and upcurved at their tips, however, with bifid tips in P. eala sp. nov. Description. Typical Poreuomena species with stridulatory area marked dark brown (Fig. 75). The stridulatory file is arched and consists of about 60 teeth, of which roughly 30 large teeth are situated in the distal part and 30 smaller and evenly-spaced teeth in the proximal part (Fig. 76). The last tergite is differentiated into two stout and downcurved processes (Figs 77,78); the subgenital plate is elongated with two outcurved lobes (Fig. 79); the cerci are stout and incurved and possess an apical flat tip with three short processes (Fig. 78).

Poreuomena magnicerca (Massa, 2013) stat. nov.
Description. P. magnicerca was described in the genus Cestromoecha, but actually belongs to the genus  Poreuomena since sharing all generic characters with this genus and lacking a mirror on the right tegmen, typical for Cestromoecha. The stridulatory area of the left tegmen is black (Figs 80, 81); the stridulatory file is long and straight and has about 50 teeth (Fig. 82) and is clearly longer and has smaller teeth than C. longicerca. The cerci are stout, long and incurved, with the basal part rounded and the apical part pointed; they appear trifid because, subapically, they have a well-developed upper laterally flattened bulge and an inner long spine (Figs 83, 84). The subgenital plate is concave, triangular and elongated, with a deep concavity and with processes positioned very close to each other (Fig. 85).
Colour. Probably predominantly green when alive, brown to tawny when preserved. The stridulatory area of the left tegmen and the area below black. Small black spots are present on the posterior margins of the tegmina.
Measurements ( Diagnosis. P. matthaei sp. nov. is a comparatively large Poreuomena species, characterised by its yellowish colour, whitish triangular areas on the left and the right tegmina and incurved cerci with a flattened blackish tip. The 10 th abdominal tergite is similar to that of P. gracilicercata sp. nov. Both species, however, have differently-shaped male cerci. While all other Poreuomena species have flaps at the bases of the tegmina, in P. matthaei sp. nov. only the area at the base of the right tegmen is developed as a flap, while on the right side, a bulge is present (Fig. 86).
Description. Male. Yellowish-cream coloured with a faint blackish stripe on the stridulatory area (Fig. 86); the triangular area close to the stridulatory file above the left tegmen and the corresponding area on the right tegmen are whitish. Antennae thin, fastigium of the vertex separated from the fastigium of the frons, face smooth, eyes round, prominent. Pronotum with a flat and smooth disc, the anterior margin straight, the posterior margin broadly rounded (Fig. 86). Tegmina narrow, ca. 10.7× broader than long; stridulatory area of the left tegmen comparatively long for the genus. Stridulatory file 0.5 mm long, with ca. 70 slightly arched teeth which are more evenly spaced at their base than at the apex (Fig. 87). Fore coxa armed, fore femora with 4 small spines on the ventral inner margins, mid femora with 5-6 small spines on the ventral outer margins, hind femora with 3-4 rows of small ventral spines distally. Fore tibiae with the tympanum conchate on the inner and open on the outer side, with 3-4 small spines on the inner margins, mid tibiae with 3-4 small spines on the outer margins, hind tibiae with numerous spines and 3 apical spurs on each side. Last abdominal tergite flattened and enlarged (Figs 88, 89), cerci basally stout, long and incurved, their tips blackish and flattened. Subgenital plate elongated with two roundish lobes (Fig. 90).
Etymology. P. matthaei sp. nov. is dedicated to the late Matteo Griggio, who at the age of 43 left us on 14 May 2020 due to an aneurysm. Matteo was a lively behavioural ecologist who was also very committed to nature conservation, curious about every particular aspect of nature, including Orthoptera as a food source for the Rock Sparrow in Sardinia.
Distribution. Presently known only from the Lope National Park (Gabon).  Diagnosis. Small and fragile species, green (alive) or brown (preserved) coloured, with a brown-reddish upper area of the abdominal tergites. The 10 th abdominal tergite of P. sanghensis is similar to P. wilverthi, however, not downcurved, but produced posteriorly with a deep median fold. The male cerci are also similar between these two species, however, much more fragile-built in P. sanghensis.

Poreuomena sanghensis Massa, 2013
Description. Typical Poreuomena species with an elongate habitus (Fig. 91). Stridulatory area of the left tegmen short and straight (Fig. 92). The stridulatory file has ca. 40 teeth, of which 7-8 are proximally placed nearly perpendicularly to the others (Fig. 93). The ventral margins of the hind femora have 2 spines. The 10 th tergite ends with two short reddish rounded flat lobes with an inner spine (Figs 94, 95); the cerci have a wide round base, with an inner spine, then becoming narrower; upcurved and pointed apically (Figs 94-96). The male subgenital plate is stout, the processes are slender and incurved, forming a circular space between them (Fig. 96).
Colour. Predominantly green when alive, brown to tawny when preserved; dorsal area of abdominal tergites brown-reddish. A black marking is present at the base of the tegmina of the male, absent in the female.
Measurements ( Distribution. Central African Republic (Dzanga-Ndoki National Park and Dzanga-Sangha Special Reserve), Cameroon (Massa 2013;2015), and Gabon (Massa, in press). Diagnosis. Similar in the outer male genitalic apparatus to P. magnicerca from further west in the Congo Basin. Differentiated from P. forcipata and P. laeglae by a different 10 th abdominal tergite which is clearly divided into two lobes in P. forcipata, while P. tshuapa sp. nov. only has small humps and the posterior margin of the 10 th abdominal tergite of P. laeglae is more-or-less straight. P. forcipata has male cerci differentiated into two branches, an outer rather blunt, finger-like part and an inner blade-like expanded branch with an acute tip, similar to the inner branch of P. tshuapa sp. nov. and P. magnicerca. However, P. tshuapa sp. nov. has an additional branch just below the finger-like part of the cerci, absent in P. forcipata, but also present in P. magnicerca (also see diagnosis at P. laeglae). In P. magnicerca, the blade-like subapical section or the "third" branch is more roundish and larger than in P. tshuapa sp. nov. and the subgenital plate differs between these two species. In P. tshuapa sp. nov., the subgenital plate is bilobate with the processes clearly separated, while in P. magnicerca, the lobes of the subgenital plate are shorter and situated more closely to each other. Further, in P. forcipata and P. laeglae, asymmetrical spines are present on the left side of the supra-anal plates.

Poreuomena tshuapa
Description. Male. Probably predominantly green when alive, preserved specimens of tawny colour (Fig. 97). Where tegmina meet when folded, interior part of cells of dark colour while surrounding and elevated veins green/tawny. Typical Poreuomena species with Rs branching off from the radius near the base. The tegmina have two typical well-developed flaps at their base, the flap on the left side smaller and more pointed than the flap on the right tegmen. Beneath the flaps, tegmina with narrow longish brown markings are typical for several Poreuomena species. The stridulatory file on the left tegminal flap is about 1.5 mm long with small broadly-spaced inner teeth becoming gradually larger and are more densely set (Fig. 98). The last third consists of very densely packed teeth becoming smaller again; the apical part is strongly curved. All-inall, the stridulatory file consists of about 70-80 teeth. Stridulatory file on the underside of the right tegmen not as well-developed, but similar in shape and size and arrangement of the teeth. The 10 th abdominal tergite has almost a straight posterior margin with only two bump-like structures laterally (Fig. 99). The cerci are stout, divided at their apical part into three branches: a subapical blade located just beneath the second elongated, finger-like branch and an inner blade-like or leaf-like expanded branch with sclerotised margins (Figs 99, 100). The subgenital plate is elongated and deeply divided into two lobes; without styli ( Fig. 100). Between the subgenital plate and the cerci, two longish internal structures are present (titillators).
Distribution. Democratic Republic of the Congo, Tshuapa Province. Griffini, 1908 Figs 101-107 Poreuomena wilverthi Griffini, 1908. Mem. Soc. entom  Re-description. Male. Typical Poreuomena species with wings protruding over the body by only a few mm (Figs 101, 102). Where tegmina meet when folded, interior part of cells of dark colour while surrounding and elevated veins green (tawny in preserved insect). Rs branching off in the first half of the basal part of the tegmen. Tegmina with two flaps at their base, the flap of the left wing smaller and more pointed than the broader flap with a rounded tip on the right tegmen. The stridulatory rib and surrounding part of the flap of the left tegmen marked dark brown, few patches of brown on right tegmen. Area beneath flap with large brown marking. Stridulatory file on the underside of left flap about 1.2 mm long; the area at the inner side of the file strongly curved; with a few small widely-set teeth (Fig. 103). This part is followed to about the middle of the file by about 16-18 large and increasingly more densely-set large teeth changing then to about 40 or more very densely-set teeth decreasing in size apically. Stridulatory file on the right tegminal flap not as strongly developed, but of similar shape and the same arrangement of the teeth. The 10 th abdominal tergite a rounded flap with a median groove and an indentation at the posterior margin giving the structure a bilobate shape (Figs 106, 107). The cerci are thick and slightly incurved with a very narrow and pointed tip (Figs 104-107). The subgenital plate is bilobate with short lobes with rounded tips (Fig. 105). Between the subgenital plate and the cerci, thick blade-like titillators are present (Fig. 107).
Distribution. Widespread west of the Albertine rift into the area of the Central African Republic. Remarks. At present only the holotype was known. The new material studied coming from the Natural History Museum of Budapest and the Africamuseum Tervuren considerably enlarges the known area of distribution of this species (Fig. 111).

3´
Cerci rather short and of normal shape, slightly in-and upbent at tips (Figs 19, 20)       In the light of these dramatic changes of the climate in the past and thus leading to fragmentation and recurrent expansion of forest cover, the high diversity found in Poreuomena could be explained. However, Cestromoecha, on the other hand is a species-poor genus with only two known species at present. Either the latter genus did not cope well with recurrent fragmentation events of its habitat and species became extinct or the picture we see is due to poor collecting activities and gaps in our knowledge of the diversity of many Central and West African taxa including Cestromoecha. In Poreuomena however, several morphological closely related species suggest a diversification during the past couple of million years, similar to time-scales of speciation found in East African Orthoptera (e.g. Schultz et al. 2007;Voje et al. 2009;Hemp et al. 2010aHemp et al. , b, 2015Hemp et al. , 2016Hemp et al. , 2018Hemp et al. , 2019Hemp et al. , 2020. All investigated Orthoptera taxa with an array of morphological closely-related species evolved more or less during the past 1-3 m years due to climatic fluctuations recurrently fragmenting and connecting forests in the Eastern Arc Mountains in Kenya and Tanzania and the old coastal forests. That iso-lation has not been 100% for this group of insects, however, as seen in genera with representatives both in Central/ West and East Africa (e.g. genera of Pseudophyllinae such as Zabalius Bolívar, 1886 or Stenampyx Karsch, 1890 or in morphologically closely-related genera, such as Tomias Karsch, 1890 in Central/West African and Pseudotomias Hemp, 2016 in East Africa; also see Hemp 2016;. Molecular analyses on wood mice of the genus Hylomyscus showed that species diversified in the Miocene, a first branch of mice branching off from Central African ancestors and reaching East Africa (Nicolas et al. 2020), while a second branch of East African mice diversified in the Pleistocene, 1-3 Ma. At the same time, Central African mice of the genus Hylomyscus diversified as well showing that major climatic changes and thus shifts of forest cover must be the reason behind this pattern seen in small mammals and analogous in Orthoptera.
In Poreuomena two morphological lineages are discernible: Lineage 1 consists of species with a (for Poreuomena) typical bilobed 10 th abdominal tergite in males or a 10 th tergite deviated from this condition (Fig. 108). The subgenital plate of the males of these species is bilobed and the cerci consist of a single branch (acute, bifurcate or with expanded tips, extremely elongated processes in P. gracilicercata sp. nov., Fig. 60). Morphologically most similar are species of Central Africa, the widespread P. wilverthi (Albertine Rift to Central African Republic), P. eala sp. nov. and P. biaculeata sp. nov., both in the Congo Basin (Democratic Republic of the Congo), P. crassipes and P. africana from Cameroon and Gabon and P. huxleyi from Equatorial Guinea (Bioko) and Cameroon (Fig. 108). Further West in the Côte dʼIvoire two species are known morphologically clearly different from the more centrally-distributed species with conspicuous male cerci expanded at their tips, P. ivoriana sp. nov. and P. lamottei. In addition, P. sanghensis distributed in the Congo Basin has bifurcate male cerci, however, not expanded. P. ivoriana sp. nov. has a flat expanded flange at the cerci. Such a flange is also found in species assigned to lineage 2, however, with elongated male cerci that are differentiated into two or three branches of different shapes, P. laeglae in the Ivory Coast, P. forcipata in Central Africa (Cameroon, Central African Republic), and P. magnicerca and P. tshuapa sp. nov., both recorded from the Congo Basin in the Democratic Republic of the Congo (Figs  109, 111). These species also have a more or less undifferentiated 10 th abdominal tergite, with a straight posterior margin to strongly globose but not bilobed as typical for many species of lineage 1.
The highest diversity of Poreuomena is found in forests between Gabon and Cameroon. The forests of this area persisted even during extremely arid times, for example during the Ice Ages as seen in various forest trees (Piñeiro et al. 2019) and could have served as refugia for Poreuomena (and other taxa, for example in plants, Linder 2014) explaining the high diversity and that numerous representatives of both lineages of Poreuomena are found in this area.

Outlook
Ultimately, molecular analyses should show the relationships of the species and lineages of Poreuomena, very likely supporting that forest remains of the once strongly-fragmented Guineo-Congolian area served as refugia for flora and fauna and a motor for diversification, analogous to the Eastern Arc Mountains in East Africa.