Pterotiltus erythrocerus Rowell & Oumarou-Ngoute, 2025, sp. nov.
Creators: name: Rowell, C. H. F.
name: Oumarou-Ngoute, Charly
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Orthoptera
Acrididae
Pterotiltus
Pterotiltus erythrocerus

description: 16. Pterotiltus erythrocerus sp. nov.
urn:lsid:zoobank.org:act: 6E6BC5F8-037B-4FA8-838E-A16192E8F464
Figs 45–48; Table 14
Etymology
Latinised from Greek ‘ erythros ʼ [‘redʼ] and ‘ keras ʼ [‘horn, antennaʼ]. Specific name selected to emphasize the most striking external feature (the red antennae) and to link the species linguistically with its taxonomic history of being originally but erroneously described as the female of apicalis rubroanntenatus.
Material examined
Holotype
CAMEROON • ♂; Nyong-et-So Division, Zamakoe Village; 668 m a.s.l.; 4 May 2018; C. Oumarou-Ngoute leg.; MfN 2017250.
Paratypes
CAMEROON • 1 ♀; same data as for holotype; MfN 2017249 • 1 ♂; same data as for holotype; MfN 2017251 • 1 ♀; Yaoundé; [3°52′0″ N, 11°31′0″ E]; 1897; von Carnup leg.; [paratype of P. apicalis rubroanntenatus Ramme, 1929]; MfN, DORSA BA000507S02 • 1 ♀; Lolodorf; [3°14′ N, 10°44′ E]; L. Conradt leg.; [paratype of P. apicalis rubroanntenatus Ramme, 1929]; MfN, DORSA BA000507S03 • 1 ♀; Bipindi; [3°04′ N, 10°25′ E]; G. Zenker leg.; [paratype of P. apicalis rubroanntenatus Ramme, 1929]; MfN, DORSA BA000507S04.
Description
Size, medium; males average ca 19 mm in body length, females ca 22 mm – see Table 14. Integument rugose and pitted on head, thoracic, and proximal abdominal tergites, but otherwise smooth and shiny.
Male
HEAD. Antennae filiform, longer than head and pronotum together. Fastigium of vertex (Fig. 46A) roughly triangular, short, wider than long, sloping forwards, slightly concave, sometimes with a weak medial carinula; the obtuse-angular apex runs smoothly into the frontal ridge. Frons oblique and straight in profile; frontal ridge clearly defined in its upper half with shallow medial sulcus but obliterated in lower half. Lateral facial carinae well defined dorsally, but obsolete below level of medial ocellus. Eyes small, almost round, strongly convex; interocular space in males equal to, in females slightly wider than, the antennal scape.
THORAX. Pronotum cylindrical, without medial or lateral carinae; three deep, wide sulci crossing dorsum, with large transverse convexities between them that project laterally between sulci 3 & 4. Metazona less than one-fifth length of prozona, its posterior margin straight, slightly concave in the midline, the anterior pronotal margin slightly produced in the midline, overhanging the occiput. Furrows between meso- and metanota and metanotum and first abdominal tergite wide and deep. Prosternal process simple, conical, acute at apex. Mesosternal interspace open, slightly longer than wide, mesosternal lobes rounded. Metasternal interspace nearly closed. Elytra and wings almost completely absent, elytron reduced to a minute immoveable cuticular scale on the mesothoracic tergite. Hind femur slender, 4.5 times as long as wide. Hind tibia only moderately expanded distally, but densely haired; external apical spine present. External tibial spurs smaller than the internal spurs. Arolium large.
ABDOMEN. Tympanum small, circular, open. Last abdominal tergite of male with a minute furcula, the paired projections separated at their tips by 0.42 mm (Fig. 46B). Male supra-anal plate widely triangular, very short. Male cercus wide at base, laterally compressed, triangular in lateral view, narrowing to spine-like apex, slightly incurved. Male subgenital plate very short, rounded.
PHALLIC COMPLEX. The ‘horseshoe’ formed by the cingulum and the cingular apodemes in dorsal view is slender. The anterior tips of the apodemes are widened and rounded, rather than pointed. Epiphallus (Fig. 47A–D) with divided bridge, ancorae absent, and large lophi; in this species the roughly triangular outer lophi are set obliquely and the pointed tips are sharply inclined cephalad, so that in axial view the lophi appear almost rectangular. There is also a pair of small inner lophi more medially on the lophal ridge (Fig. 49A, D). The ‘oval’ sclerites are roughly teardrop-shaped. The epiphallic membrane contains a ventrolateral sclerite, encircling the ventral half of the phallus. The ventrolateral sclerite is unusually variable in this species. In most individuals it forms the usual half hoop surrounding the ventral half of the ectophallus, its tips running obliquely upwards and rearwards in the ectophallic membrane to a point just anterior to the cingular rami. In some individuals, however, the sclerite takes the form of 2 oblique bands which touch or overlap in the ventral midline but are not joined together. The overlapping ends are widened – perhaps the origin of the ventral flange? This observation suggests that the ventrolateral sclerite of Pterotiltus was originally a paired structure, now fused in most species. Endophallus (Fig. 47E–F) with a slender flexure, which ends as a short spatulate endophallic process, applied closely to the ventral aedeagal sclerite. Cingular valves fused and elaborated together with the arch sclerite into a valvular plate (Hollis 1971, 1975) covering the aedeagus dorsally and laterally. The anterior part of the plate is saddleshaped and fits over the dorsal surface of the edeagus. The terminal lateral lobes of this plate are concave, cupped around the medial lobes, which form two vertical rounded lamellae (Fig. 48A–E).
Female
Dorsal valves of ovipositor laterally compressed, with obtuse apices; ventral valves smooth, slender, straight, rod-like, sometimes dorsally flattened or slightly grooved. Egg guide prolonged horizontally rearwards between the ventral valves, up to half the length of the latter, rod-shaped, straight or weakly curved, sharply pointed. Female subgenital plate simple, its ventral surface smoothly rounded; hind margin curves inwards to base of egg guide (Fig. 48F). Bursa copulatrix large, sac-like, spermatheca with small apical diverticulum and a large curved subapical diverticulum (Fig. 48G).
Colouration
Male and female are identically coloured (Fig. 45).
HEAD.Antennae uniformly red, without white tips. Eyes black, drying to yellow grey. Vertex and fastigium sometimes tinted red (see Fig. 45B). Margins of antennal sockets and the edges of the fastigium anterior to the lateral ocelli, often red. Genae behind eye blue-black, below eye white. Frons white with green or brown mottle. Clypeus and labrum white, heavily mottled with blue-green and black. Sides of mandibles dark blue-green.
THORAX. Pronotum shiny black, with paired white patches near both posterior and anterior margins of the disc. The white of the subocular genae continues along the lower margins of the lateral pronotal lobes, but is interrupted by black between sulci 1 and 2. Pleura and terga of meso- and metathorax black, with blurred white patches on both episterna. In some individuals the pronotal disc and the thoracic terga are blotched with red. All legs green, drying to yellow. Hind knee and condyle of hind tibia red, tibial shaft and tarsi dark blue green.
ABDOMEN. Abdominal tergites 1 to 3 black, with paired white patches on Abd. 1. In some individuals, the Abd. 1 tergite is red. Abdominal tergite 4 dirty white, remainder of abdomen green, drying to yellow. The tip of the abdomen is never red in this species.
Sexual dimorphism
Table 14 (below) shows that the length of the male pronotum (P) is 0.89 times that of the female. The ratio of their body lengths (L), however, is 0.88 – this discrepancy is due to a measurement error in the male body length caused by the upwardly inflected male genital segments. When the various measurements are normalised by dividing their averages by P, their male:female ratios mostly approach unity, showing that the body proportions are identical in the two sexes. The exceptions (which are typical of the genus as whole) are a) the male antennae are proportionately much longer (M/F = 1.39), and b) the male interocular space is proportionately smaller (M/F = 0.80).
Measurements
See Table 14.
Taxonomic history
Ramme (1929) erected the taxon P. apicalis rubroantennatus to cover a variety of specimens of Pterotiltus present in European museums, which had as their common feature their entirely red antennae. The holotype male (now P. rubroantennatus stat. nov.) from Cross River has been treated above (p. 30). The remainder of his type series comprised (a) a male paratype from the very distant Faradje (DR Congo); this specimen appears to be of a distinct species,which we discuss below (p. 97) under “Additional species requiring further collections before description” and (b) the female paratypes now transferred to P. erythrocerus sp. nov., from a different part of Cameroon.
The three female paratypes of Ramme’s P. apicalis rubroantennatus, MfN DORSA BA000507 S02 to DORSA BA000507 S04 (see p. 77), are included in this new species, and are here considered to be additional paratypes of it. Ramme’s female paratypes (all examined) are specimens from three localities on the South Cameroon Plateau. All have red antennae, and some of these individuals have additional red colouration on the fastigium, pronotum or head, but they all lack the red abdomen of Ramme’s holotype. Conradt’s specimen was collected probably in the 1890s, but certainly before 1905, as it was cited in Bolívar’s article of that year (other Conradt specimens of grasshoppers from Cameroon are labelled 1896–1899).
To investigate Ramme’s paratypes, and especially to examine the previously unknown males of this taxon, we collected and examined recent samples of Pterotiltus spp. from four different localities on the South Cameroon Plateau, close to the localities of Ramme’s specimens. It comprised 22 adults: 10 individuals from Ongot, nr Yaoundé; 9 individuals from Zamakoe; 2 individuals from Ngoutedjap; 1 individual from Bipindi.
They fall into two groups in their colouration, and in their epiphallic structure. Most specimens have red antennae and some of these also have minor red colouration on the fastigium, and/or the pronotum. The females of this group are indistinguishable from Ramme’s rubroantennatus females. The males’ epiphalli have heavy, wide, rather oblong outer lophi, and also a pair of smaller ‘inner lophi’ on the lophal ridge (see Fig. 47).
A minority, however (all from Ongot), have blackish brown antennae (but not shiny black as in P. nigroantennatus), and no red on head or thorax, and the hind knees are less vibrantly red in colour. These males have slim, tapering, crescent-shaped outer lophi, and lack inner lophi completely.We describe this form below (p. 85) as P. sobrius sp. nov.
What is the relation of this modern population to Ramme’s type of P. apicalis rubroantennata? The male of erythrocerus lacks the red abdomen of Ramme’ male holotype. We compared the phallus of his holotype (Fig 16) with that of erythrocerus. The holotype of rubroantennata has a different shape of epiphallus. The lophi are crescentic, but broader than in erythrocerus, and there is no inner lophus on the lophal ridge. We conclude that there are three different taxa within Ramme’s “ apicalis rubroantennata ”:
a) P. rubroanntenatus Ramme, 1929 stat. nov. (i.e., Ramme’s holotype male from Ossidinge)
b) the “Faradje male” paratype (see below, p. 97, an undescribed species)
c) Ramme’s paratype females from South Central Cameroon (= P. erythrocerus sp. nov.).
All three species have red antennae.
Distribution
South Cameroon Plateau, from Ongot and Yaoundé in the north, west to Bipindi and Boumnyebel, and South to Ngoutadjap. In Ongot it is sympatric with P. sobrius sp. nov. Bipindi is on the road from Kribi to Lolodorf, at Km 75; Lolodorf is at Km 110.
Boumnyebel is on route N3 from Doula to Yaoundé, just a little east of the border between Littoral and Central Divisions; coordinates 3.883694° N, 10.848956° E, Dept Nyong-et-Kéllé.
Status of taxonomic material
Good. Both sexes known, adequate numbers of specimens available, and modern localities known.
description: Published as part of Rowell, C. H. F. & Oumarou-Ngoute, Charly, 2025, Review of Pterotiltus Karsch, 1893 (Orthoptera, Acrididae, Oxyinae), pp. 1-104 in European Journal of Taxonomy 986 on pages 77-84, DOI: 10.5852/ejt.2025.986.2853, http://zenodo.org/record/15235428