The finding came out of a systematic survey conducted between July 2025 and February 2026 on two peaks of the Cameroon Volcanic Line, a chain of mountains and islands running from the Gulf of Guinea inland through Cameroon that ranks among the most significant montane systems in West and Central Africa. The team, working under permit-free sweep-net protocols and targeting grasshoppers for sixty minutes per sampling day between mid-morning and late afternoon, collected a total of 22 individuals belonging to the genus Occidentosphena. Fourteen of them, nine males and five females, gathered in gallery forest on Mount Manengouba on 29 September 2025, turned out to be O. ruandensis. The remaining eight, collected on Mount Bamboutos at 2,440 meters in an agricultural field, represented the second species of the genus, O. uvarovi, confirming that thisCameroonian endemic still persists in the country more than a century after its type specimen was taken.

The biogeographic significance of the Manengouba record is difficult to overstate. Until now, O. ruandensis was known only from the Eastern Afromontane region around Lake Kivu and the Albertine Rift, with its holotype, a female deposited in the Museum für Naturkunde in Berlin, collected on Mount Niragongo in 1907. Its sister species, O. uvarovi, was believed to be restricted to the Cameroonian highlands until recent reviews of edible Orthoptera reported it from Congo and Gabon, hinting that the genus may be far more widespread than museum drawers suggest. The authors argue that the apparent restriction of O. ruandensis to the Albertine Rift may never have reflected a true biogeographic pattern at all, but simply the consequences of limited sampling across the poorly surveyed mountains of West and Central Africa.

Two scenarios could explain the new distribution map. The first is that O. ruandensis has always maintained a fragmented, disjunct range, with isolated populations clinging to separate montane blocks much as other Afrotropical orthopterans do. The second is that the species once occupied a broader continuous range that was later carved into refugia by climatic fluctuations, geological events, and, increasingly, by human activity. Agricultural expansion, pesticide use, and pastoralism are all transforming the grasslands of Mount Bamboutos, where gallery forests and mountain meadows have been largely converted into crop fields, eucalyptus plantations, and pastures. Comparable patterns of fragmentation driven by habitat destruction and natural habitat patchiness have been documented in other montane African katydids and grasshoppers, lending weight to the idea that Occidentosphena populations are relics of a once more connected fauna.

Beyond the range extension, the study delivers the first detailed descriptions of the male genitalia of both species, a technical milestone with real taxonomic consequences. Grasshopper systematists have long recognized that external morphology alone can be misleading when separating closely related montane taxa, and the genus Occidentosphena is a case in point. Both species were originally placed in the genus Parasphena on the basis of external characters, with O. ruandensis described from females in 1914 and O. uvarovi from males in 1942. Kevan’s 1956 revision of the African Pyrgomorphinae erected Occidentosphena and transferred both species into it, later synonymizing Chopard’s Parasphena granulata, described from female specimens, with Rehn’s O. uvarovi. Since then, identification within the genus has rested on shaky, incomplete comparisons.

The new material allowed the team to dissect and image the phallic complexes of both species under a high-resolution digital microscope, following established preparation protocols, and to formalize a suite of genital characters that reliably diagnose the two taxa. In O. ruandensis, the lophi of the epiphallus bear a bilobed apex, the apodemal plate of the cingulum is ovoid in lateral view with ventrally produced lobes ending in rounded tips, the valves of the cingulum are visible in ventral view and extend beyond the sheath of the ectophallus, the dorsal cleft of the cingulum is hidden beneath the aedeagal valves, the sheath’s apex is nearly straight, and the ventral process of the cingulum broadly covers the endophallic apodemes. O. uvarovi shows the mirror image of this constellation in several respects: lophi with an acute, unilobate apex, a rounded apodemal plate with acute ventral lobes, cingulum valves invisible in ventral view, a large dorsal cleft, a broad V-shaped ventral cleft, a sheath with a rounded apex, and a ventral process that entirely conceals the endophallic apodemes and even reaches the basal thickening of the cingulum.

External traits corroborate the genital differences. O. ruandensis is predominantly green in both sexes, with black eyes lacking the white banding seen in its relative; males have yellowish to bluish femora and blue to green tibiae, while females are green throughout with light green ovipositor valves tipped in yellow. O. uvarovi males are predominantly brown with whitish granules and grey eyes marked by two horizontal white bands, whereas females are light green with brown or burgundy fore and middle femora, greenish-yellow hind femora, and reddish hind tibiae and ovipositor. Morphometric analysis of ten body measurements, compared statistically between species for each sex separately, found only limited separation: significant differences emerged in male head length, pronotum length, and pronotum width, while females of the two species were statistically indistinguishable in nearly every measured trait, underscoring why genital anatomy is the more dependable key.

The ecology of both species adds another layer of intrigue. All O. ruandensis specimens were taken during the rainy season in an open herbaceous zone at the edge of a montane gallery forest beside a small permanent stream, suggesting that seasonal activity patterns may render the species nearly undetectable during drier months. No previous grasshopper survey had specifically targeted Mount Manengouba, so it remains unclear whether the species is genuinely rare there or simply evaded collection until now. O. uvarovi, by contrast, was found in an actively farmed field at 2,440 meters on Mount Bamboutos, a habitat far more disturbed than the forests its ancestors likely occupied, hinting at at least some ecological flexibility in a genus otherwise associated with specialized montane environments.

Both species share the hallmark adaptations of wingless montane grasshoppers: tegmina and wings are entirely absent, though a tympanum is present, and their thick, filiform antennae and slender hind legs suit life in dense herbaceous vegetation where flight would be a liability. Females are markedly larger than males, ranging from about 20.7 to 25.1 millimeters in body length compared with roughly 12 to 16 millimeters for males, and their long, compressed ovipositors with outwardly or inwardly curved valve tips provide further diagnostic cues. These traits, typical of flightless insects on isolated highlands, make Occidentosphena an excellent model for studying how mountain barriers shape diversification across the African continent.

The researchers emphasize that their work is a beginning rather than an end. The Cameroon Highlands are recognized centers of endemism, yet their orthopteran fauna remains astonishingly underexplored relative to the better-studied Eastern Afromontane hotspots. Future integrative studies combining extensive field sampling with morphological and molecular data are expected to reveal additional hidden diversity within Occidentosphena and to clarify how its two species came to be separated by thousands of kilometers of lowland forest and savanna. For now, the green grasshopper of Mount Manengouba stands as a reminder that even on well-mapped mountains, the smallest inhabitants can still redraw the map of African biodiversity.

Subject of Research: First record of the grasshopper Occidentosphena ruandensis in Cameroon and re-description of Occidentosphena uvarovi from the Cameroon Volcanic Line

Article Title: First record of Occidentosphena ruandensis (Rehn, 1914) in Cameroon, and re-description of Occidentosphena uvarovi (Rehn, 1942) ( Orthoptera , Pyrgomorphidae ) from the Cameroon Volcanic Line

Article References: First record of Occidentosphena ruandensis (Rehn, 1914) in Cameroon, and re-description of Occidentosphena uvarovi (Rehn, 1942) ( Orthoptera , Pyrgomorphidae ) from the Cameroon Volcanic Line. (n.d.). https://doi.org/10.3897/afrinvertebr.67.195122

Image Credits: AI Generated

DOI: 10.3897/afrinvertebr.67.195122

Keywords: Occidentosphena, grasshoppers, Pyrgomorphidae, Orthoptera, Cameroon Volcanic Line, Mount Manengouba, Mount Bamboutos, montane endemism, biogeography, male genitalia, taxonomy, Afromontane biodiversity

The Noun Plain is, in volcanological terms, a compressed textbook. Within a few tens of kilometers, phreatomagmatic maars formed where rising magma met groundwater, basaltic scoria cones built by Strombolian explosions, polygenetic volcanic complexes, and felsic intrusive domes all coexist in unusual spatial proximity. The basement consists of Pan-African granitic plutons and migmatitic gneisses, dissected by major tectonic fractures that channeled successive eruptions. Regional volcanism unfolded in three macro-phases: an early fissural effusive episode producing Tertiary flood basalts and rhyolites, a central phase constructing viscous rhyolitic domes and flows, and a final Plio-Quaternary explosive phase of synchronized Strombolian and phreatomagmatic events that sculpted the modern landscape. The erupted products trace a classic alkaline lineage from basanites and alkali basalts to trachytes and rhyolites, and recent petrological work on young pyroclastic deposits at Petpenoun and Baïgom has yielded clues about garnet-lherzolite mantle sources beneath the line.

To evaluate this heritage objectively, the team applied the Brilha methodology, a widely used quantitative framework that deliberately separates scientific value from potential educational and touristic use, and adds a degradation risk module. Scientific value was scored across seven criteria, with representativeness weighted at 30 percent, key locality at 20 percent, and integrity and rarity at 15 percent each, producing standardized scores from 100 to 400 points. Potential educational use emphasized accessibility and school-group suitability, while potential touristic use weighted landscape quality and accessibility at 15 percent each and explicitly credited the region’s Bamoun intangible cultural history. Degradation risk combined five factors, dominated by the vulnerability of geological components at 35 percent, alongside proximity to degrading activities, legal protection, accessibility, and population density. Nineteen geosites were classified into four morpho-volcanic categories: maars, scoria cones, polygenetic complexes, and felsic intrusive products.

The scientific headline is the Mbapit Massif, whose rhyolitic peak scored 395 for scientific value, the joint highest in the inventory. The massif is a composite volcano-plutonic complex reaching 1,988 meters, encompassing the South Volcano and the Mfou maar, and it provides outstanding morphological evidence of bimodal magmatism, the coexistence of mafic and felsic melts that marks a critical stage in the evolution of the Cameroon Volcanic Line. Equally significant are the Nkoambeng and Kechuentim scoria cone complexes, which scored 395 and 380 respectively. Their pyroclastic successions contain green-core clinopyroxenes, iron-rich crystal cores mantled by magnesium-rich rims, which microprobe analyses have shown to be direct petrographic evidence of deep magma mixing and mantle source heterogeneity. These small green-zoned crystals, invisible to casual visitors, record open-system magmatic processes operating beneath the African lithosphere, placing the Noun Plain on the global petrological map.

Lake Monoun, scoring 390 for scientific value, carries a darker and world-famous legacy. In 1984 the lake released a limnic eruption, a catastrophic burst of carbon dioxide that had accumulated in its deep waters, killing dozens of people and launching decades of international research on gas-charged crater lakes. The lake’s polygenetic maar structure, with internal walls exposing listric faults in the Pan-African basement, now doubles as an exceptional outdoor classroom, and its position near major roads makes it readily accessible to school groups. The study stresses that continued geochemical monitoring of Monoun remains essential, both as a hazard mitigation priority and as a living scientific record of one of the planet’s rarest natural phenomena.

Where the science peaks, so does the culture. Petpenoun, a rare volcanic dam formed when ancient Nkoambeng lava flows blocked the local river system to create twin lakes, earned the highest touristic score of the entire assessment at 395. Its geological origin maps directly onto the Bamoun Legend of the Twins, a mythological account of the lakes’ creation, and the site’s low degradation risk of 120 suggests this fusion of natural and cultural heritage is being conserved effectively. Lake Mfouet offers an even more striking example: its emerald waters serve as the permanent site of Bamoun community initiation rites, and that sacred status has achieved what formal law has not, holding degradation risk to just 180 in a region where legal protection is largely absent. The authors argue that such traditional taboos function as an invisible but highly effective governance tool.

The contrast with the study’s starkest numbers could not be sharper. The Njigoumbe intrusive dome, despite its scientific importance, recorded the maximum degradation risk of 400 in the entire inventory, driven by intense industrial quarrying, while the Chapchap cone scored 380 under combined pozzolan extraction and agricultural expansion. Nkoambeng itself faces a risk score of 360. These figures, the researchers write, expose a systemic failure in territorial management: geosites treated as material mines rather than non-renewable natural heritage. Their proposed remedy is a multi-use zonation strategy, with sanctuary zones fully protecting unique features such as the clinopyroxene-bearing outcrops, controlled buffer zones permitting limited artisanal extraction on less significant flows, and economic reorientation toward geotourism anchored at Petpenoun’s existing facilities.

To translate the scores into action, the team lays out a four-phase roadmap toward a UNESCO candidacy. Phase one secures national natural monument status for top-tier sites and delineates the Geopark perimeter. Phase two establishes a management body integrating regional administrators with traditional Bamoun authorities, paired with training programs for local youth. Phase three deploys multilingual interpretive signage in French, English, and Bamoun at hubs such as Mfoumben, an archetypal stratovolcano with the region’s highest educational score at 380, and Lake Monoun. Phase four links individual trails into a unified geocultural circuit, including a proposed bridge over the Noun River to connect the Neghop-Ghang and Mfouet clusters into a one-day itinerary, culminating in submission of the formal application to the UNESCO Secretariat. Training young Bamoun geoguides is central, converting volcanic landscapes into livelihoods that do not require their destruction.

The broader significance extends well beyond Cameroon. Africa remains dramatically underrepresented on the UNESCO Global Geopark list, and the Noun Plain study offers a replicable template for other under-documented volcanic regions: merge existing regional inventories, apply a standardized quantitative framework that decouples science from tourism, and build conservation on cultural foundations that already exist. The Water and Fire framework, pairing the plain’s hydrovolcanic lakes and maars with its scoria cones and magmatic intrusions, demonstrates how geodiversity can be structurally rooted in local identity rather than imposed from outside. If the roadmap succeeds, the plain where killer gases, green-cored crystals, and sacred twin lakes coexist could become Central Africa’s next World-class geoscience destination, proving that the most effective protection for geological heritage is sometimes written not in legislation but in legend.

Subject of Research: Quantitative geoheritage assessment of volcanic geosites in the Noun Plain, Cameroon, for UNESCO Global Geopark candidacy

Article Title: Quantitative assessment and valorization of the Noun Plain volcanic geoheritage in Cameroon for a UNESCO Global Geopark

Article References: Ziem à Bidias, L. A., Mouchili Nguegni, S., Kouske, A. P., Ilouga, D. C. I., Njeuatchoua Kameni, L. H., Nsangou, A., Kenna, H. S., Moundi, A., & Kamgang, P. (2026). Quantitative assessment and valorization of the Noun Plain volcanic geoheritage in Cameroon for a UNESCO Global Geopark. Discover Geoscience, 4(1), Article 328. https://doi.org/10.1007/s44288-026-00698-w

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00698-w

Keywords: geoheritage, geotourism, UNESCO Global Geopark, Cameroon Volcanic Line, Noun Plain, maars, scoria cones, bimodal magmatism, magma mixing, Lake Monoun, Bamoun culture, geoconservation