Review of Pterotiltus Karsch, 1893 (Orthoptera, Acrididae, Oxyinae) Author Rowell, C. H. F. 2CE1D80A-0864-44A3-8046-220042333B70 Zoological Institute, Department of Environmental Sciences, University of Basel, Switzerland. hugh.rowell@gmail.com Author Oumarou-Ngoute, Charly 1AA321F8-AD2A-469B-87DB-D86DC5778004 Zoology Unit, Department of Biology of Animal Organisms, Faculty of Science, University of Douala, Cameroon. coumaroungoute@gmail.com text European Journal of Taxonomy 2025 2025-04-03 986 1 104 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2853/12963 journal article 309386 10.5852/ejt.2025.986.2853 4b8a8b8e-0ad0-484b-83ac-efa865c16109 2118-9773 15235428 DAA7DC3A-8804-4484-A83B-BB2C66197A08 Genus Pterotiltus Karsch, 1893 Pygostolus Karsch, 1891: 192 (junior homonym of Pygostolus Haliday, 1833 , Hymenoptera ). Pterotiltus Karsch, 1893: 108 (replacement name for Pygostolus Karsch, 1891 ). Type species Pygostolus impennis Karsch, 1891 . (The name Pygostolus was preoccupied, replaced with Pterotiltus by Karsch 1893 ). Generic diagnosis Modified from Dirsh (1965) , and Hollis (1975) . Etymology From the Greek “ pteros ”, “wing” or “fin”, and “ tiltos ”, “shredded, ruined”, presumably an allusion to the microptery or aptery of the genus. Description Small to medium size (average body length males 14–22 mm , females 18–27 mm ). Integument often rugose and pitted on head, and on thoracic and proximal abdominal tergites, but otherwise smooth and shiny. HEAD . Antennae filiform, 22 segments, longer than head and pronotum together, especially in males (after allowing for body size differences, the male antennae are up to half as long again as those of the female). Fastigium of vertex roughly triangular, short, wider than long, sloping forwards, slightly concave, sometimes with a weak medial carinula or groove; the obtuse-angular apex runs smoothly into the frontal ridge. Frons oblique and sometimes slightly incurved in male, in female almost vertical or only slightly oblique; frontal ridge clearly defined in its upper half with a medial sulcus, but weak or absent in lower half. Lateral facial carinae complete. Eyes small, almost round, strongly convex, slightly more protuberant in males than in females; interocular space in males narrower, in females slightly wider, than antennal scape. THORAX . Pronotum cylindrical, without carinae, or with only a slight trace of a medial carina; three deep, wide sulci crossing dorsum, often with large transverse convexities between them. Metazona short, maximally about one-third length of prozona, usually much less, its posterior margin straight or slightly concave. Anterior pronotal margin weakly produced in the midline, overhanging the occiput. Transverse furrows between meso- and metanota and between metanotum and first abdominal tergite wide and deep. Prosternal process simple, conical or cylindrical, but always pointed at apex. Mesosternal interspace open, about as wide as long or sometimes longer than wide, mesosternal lobes rounded. Metasternal interspace nearly closed. Elytra and wings micropterous, vestigial, or absent. Hind femur slender, its tip exceeding the end of the abdomen. The lower lobes of the hind knee acutely pointed, as is typical of almost all members of the Oxyinae . LEGS . Hind tibia only moderately expanded distally; internal tibial spurs larger than external spurs. Usually 7 external, 9 internal hind tibial spines. External apical spines always present. Arolium large. Fig. 1. Pterotiltus spp. Diagramatic sketch to show the anatomy of the fully extended phallus when viewed from the left hand side. Sclerites are shaded, ectophallic membrane shown in stipple. The genital duct (ejaculatory duct → ejaculatory sac → spermatophore sac) that runs medially through the phallus, is indicated in red. All the species of the genus have a phallus of this type, although there are interspecific differences in the structure of some of the sclerites, especially the valvular plate and the ventral aedeagal sclerites, and to a lesser extent in the epiphallus and the ventral flange of the ventrolateral sclerite. For explanation of abbreviations, see Material and methods (pp. 4–5). ABDOMEN . Tympanum small, open. Tenth abdominal tergite of male partially divided, usually with a minute furcula, but in some species or individuals the paired projections fuse to a greater or lesser extent, to form a single medial process or a medial tubercle. Male supra-anal plate widely triangular, very short. Cercus laterally compressed, wide at base, narrowing to an acute or spine-like apex, triangular in lateral view, straight or slightly incurved in dorsal view. Male subgenital plate very short, rounded. PHALLIC COMPLEX ( Fig. 1 ). Epiphallus with divided bridge ( Hollis 1975 ), ancorae absent or greatly reduced, and large lophi; the outer lophi are long, slender, blade-like and curved forwards. Smaller inner lophi additionally present in some species. Epiphallic membrane also contains a unitary ventrolateral sclerite, encircling the ventral half of the phallus. The anterior edge of this sclerite is usually somewhat produced forward in the ventral midline, forming a small, sclerotized plate in the membrane, here referred to as the ventral flange; it varies in shape between species. Cingular valves absent, presumed fused and elaborated together with the arch sclerite into the roughly selliform valvular plate ( Hollis 1971 , 1975 ) covering the aedeagus dorsally and partially laterally. In most species of Pterotiltus this plate is ornamented with complex cuticular folds and lamellae, often of species-specific form. Endophallus with a slender sclerotized flexure, terminating abruptly in short spatulate endophallic processes that are appressed to the ventral aedeagal sclerites. Aedeagus composed of the valvular plate and the ventral aedeagal sclerites, together with the sheathing ectophallic membrane. The ventral aedeagal sclerites too are often species-specific in shape. Their posterior extremities are the ventral aedeagal “valves”. FEMALE REPRODUCTIVE STRUCTURES ( Figs 2 , 24A , 50F–G ). Dorsal valves of ovipositor laterally compressed, with tapering apices, leaf-shaped in lateral view, often deeply grooved on their dorsal edges; ventral valves smooth, slender, straight, rod-like, sometimes dorsally flattened or slightly grooved. Egg-guide prolonged horizontally rearwards as a stiff rod between the ventral valves, up to half the length of the latter, straight or weakly curved, sharply pointed. Ventral surface of female subgenital plate flat or smoothly rounded. Bursa copulatrix large, sac-like, spermatheca with small apical diverticulum and a large curved subapical diverticulum ( Fig. 2C–D ). Key to species of Pterotiltus All species are extremely similar in external morphology, this key is therefore based on colouration in life and provenance. It applies to males only, unless otherwise stated, but the two sexes are usually similarly coloured. As colouration is often labile, especially in museum specimens, a serious determination should always be checked by a phallic examination and detailed comparison with the description of the species. 1. Hind knee blue-black or black in lateral view .............................................. .................................... 2 – Hind knee red or brown in lateral view ............................................................................................ 3 2. Antennae black with white tips. Dorsum of pronotum black with about 4–6 pale (white or yellow) spots .......................................................................... P. hollisi Rowell, 2005 (S & W Uganda, p. 60) – Antennae green basally, flagellum red. Dorsum of head and thorax blue and red ............................. ............................................. P. campoensis Oumarou-Ngoute & Rowell, 2024 (S Cameroon , p. 72) – Antennae brownish green; upper frons, genae, dorsum of pronotum black; metathoracic tergum bright yellow, small montane species ............................................................... ...................... P. inuncatus ( Karsch, 1892 ) (northern race) (NW Cameroon , E Nigeria , CRS, p. 16) 3. Hind knee brown ............................................................................................................................... 4 – Hind knee red .................................................................................................................................... 5 4. Frons and genae yellow. In female, femora of fore and middle legs red, hind femur green, hind tibia blue, apex of abdomen yellow-green (male unknown) ...................................................................... ........................................................................ P. giorgii Ramme, 1929 (NCentral DR Congo , p. 49) – Thorax & 1 st abdominal tergite uniform light brown colouration, head black and white, abdomen and legs green, antennae black with white tips ......................................................................................... ..................................... P. occipitalis Ramme, 1929 ( Cameroon , N DR Congo , West Uganda, p. 51) – Antennae blackish brown, with paler brown tips several segments in length. Genae and spots of lateral pronotal lobes white. Otherwise colouration only black or green ........................................... ..................................................................................... P. sobrius sp. nov. (C & W Cameroon , p. 85) 5. Hind knees red/brown, antennae mostly black ................................................................................. 6 – Hind knees red/brown, antennae mostly brown ............................................................................... 7 – Hind knees red, antennae solid red, no pale tips ............................................................................... 8 6. Antennae black. Abdominal apex red; frons and genae white; hind femora green with prominent darker chevron markings; hind tibia blue green; male furcula replaced by a vertical medial process ........................................................... P. impennis ( Karsch, 1891 ) ( Cameroon , Nigeria , CRS, p. 10) – Antennae black with minute pale tips. Abdominal apex red; head, thoracic and most abdominal tergites black, metazona yellow or white. Hind femora green, hind tibia pale blue ........................... ................................................................. P. miniatulus Karsch, 1893 (NE Ghana , NW Togo , p. 22) – Antennal flagellum shiny black, tips unknown. Frons and genae yellow, hind tibia green. Abdominal tip red ................................. P. nigroantennatus Bolívar, 1908 stat. nov. (Central DR Congo , p. 33) – Antennae black, with prominent white tips (fading in dried specimens). Frons and genae white, legs green, apex of abdomen red. Head and thorax black, strongly tinged with blue in fresh specimens. Polymorphic for male furcula/median tubercle .................................................................................. ................................................ P. coeruleocephalus Bolívar, 1905 (W Cameroon , E Nigeria , p. 36) – Antennal flagellum black basally, tip segments shading to light brown. Legs and apex of abdomen green. Hind knee red or reddish brown. Hind tibia dark green. In fresh specimens compound eye with a violet cast. Large robust species ............................................................................................. ............................................. P. ngoylaensis Oumarou-Ngoute & Rowell, 2024 (E Cameroon , p. 66) 7. Antennae brown, femora of pro- and meso-thoracic legs red, hind tibia black .................................. .................................................... P.biafrensis sp. nov. (coastal Rio Muni , Equatorial Guinea , p. 92) – Antennae brown, small yellow tips. Abdominal apex red. Hind femur green, but red at base. Hind tibia blue-green .................................................. P. femoratus Ramme, 1929 (SW Cameroon , p. 45) – Antennae brown, white tips. Female abdomen red, hind femur and tibia green, condyle red. (Male unknown) .................................... P. apicalis Bolívar, 1905 (Bioko Island, Equatorial Guinea , p. 28) – Antennae light greenish brown. Metathoracic tergite and abdominal tergites 1–4 bright yellow or red, frons and genae white, small montane species ............................................................................ .................................................. P. inuncatus ( Karsch, 1892 ) (southern race) (SW Cameroon , p. 19) – Antennae light brown (tip colour unknown). Frons and genae light brown. Legs green, hind knee reddish brown, hind tibia olive. Apex of abdomen red in female, perhaps in male too. Labrum and clypeus of female red. (Male colouration uncertain) ................................. P.berlandi Ramme, 1929 ( Rio Muni , Equatorial Guinea (see text pp. 56_57 for discussion; p. 57) 8. Antennae red, frons and lower genae yellow, legs green, hind tibia blue grey, apex of abdomen green ................................................................................... “Faradje male” (NE DR Congo , p. 97) – Antennae red, Frons and lower genae white...................................................................................... 9 9. Antennae red, frons and genae white. Abdomen tip male red (female unknown) ............................. .................................................... P. rubroantennatus Ramme, 1929 stat. nov. (W Cameroon , p. 30) – Antennae red, frons white with green mottle. Abdomen tip green, legs green, hind tibia blue-green with red condyle ............................................................. P. erythrocerus sp. nov. ( Cameroon , p. 77) Species diagnoses We first treat the previously described species in their chronological order of description.