Pterotiltus coeruleocephalus Bolívar, 1905

Rowell, C. H. F. & Oumarou-Ngoute, Charly, 2025, Review of Pterotiltus Karsch, 1893 (Orthoptera, Acrididae, Oxyinae), European Journal of Taxonomy 986, pp. 1-104 : 36-45

8. Pterotiltus coeruleocephalus Bolívar, 1905

Figs 19–24 ; Table 6

Pterotiltus coeruleocephalus Bolívar, 1905: 227 .

Pterotiltus coeruleocephalus – Kirby 1910: 386. — Ramme 1929: 313, designates the lectotype by inference of type. — Johnston 1956: 258. — Dirsh 1965: 236. — Hollis 1975: 226. — Mestre & Chiffaud 2009: 105.

Type material

Lectotype

CAMEROON • ♂; no locality data; 1898–99; L. Conradt leg.; MNCN, MNCN_Ent 119720 . We were unable to borrow this specimen, but were provided with good photographs of it ( Fig. 19 ).

Other material examined

CAMEROON • 1 ♂; Bounépoupa ; [4°04′49″ N, 10°02′15″ E]; 16 May 2023; C. Oumarou-Ngoute leg.; RC 192023MII • 1 ♀, same data as for preceding; RC 182023 MII • 2 ♂♂; Littoral Division , Yabassi; [4°27′30″ N, 9°58′15″ E]; 15 Apr. 2015; C. Oumarou-Ngoute leg.; RC 2021035 , 2021039 • 1 ♀; same data as for preceding; ONC 072023MII • 1 ♀; same data as for preceding; ONC 062023MII • 1 ♂; Littoral Division , Yabassi; 16 May 2023; C. Oumarou-Ngoute leg.; RC 172023MII • 1 ♂; same data as for preceding; ONC 162023 MII • 1 ♂; Littoral Division , Djawara; [3°04′ N, 10°08′ E]; 8 May 2023; C. Oumarou-Ngoute leg.; ONC 022023MII • 2 ♂♂; Haut Nyong Division , Lobéké National Park; [2°16.667 N, 15°38.775 E]; 8 Dec. 2023; C. Oumarou-Ngoute leg.; ONC 7492023D , 7502023D • 1 ♀; Haut Nyong Division , Lobéké National Park; [2°16.667 N, 15°38.775 E]; 8 Dec. 2023; C. Oumarou-Ngoute leg.; ONC 7482023D

NIGERIA • 1 ♂; Akwa Ibom State, Stubbs Creek Forest Reserve ; [between 4°32′ N to 4°38′ N, 7°54′ E to 8°18′ E]; J. Reid leg.; Oct. 1988; NHMUK, CIEA 20564 ( Fig. 21A ) • 1 ♂; Cross River State, Calabar, nr Unget ; 13 Oct. 1981; J. Reid leg.; NHMUK, CIEA 14152 ( Fig. 21B–C ) • 1 ♂; Cross River State, Calabar, Bakoko ; [4°58′37″ N, 8°20′19″ E]; 5 Apr. 1985; J. Reid leg.; NHMUK, CIEA 20564 .

Description

Male

Bolívar’s 1905 description of the male (made from dried museum material) is mostly adequate. Freshly caught males are predominantly blue, with green legs, red abdomens and red hind knees. However, Bolívar omits some features which are probably only to be seen in fresh material. In life both sexes have red fastigia and blackish brown antennae with white tips ( Figs 20 , 22 ). In dried specimens ( Figs 19 , 21 ) the antennal tips darken and the red colouration on the head fades.

HEAD. Antennae filamentous, longer than head and pronotum together, blackish brown with white tips, but drying to darker, scape and pedicel dark green. Fastigium finely punctate, red. Vertex blue-black, with two strips of punctate cuticle converging forward towards the interocular space. Frontal ridge present dorsally above the medial ocellus, sulcate, with the lateral carinae red in colour, but obsolete below ocellus. In modern Cameroonian specimens ( Fig. 20 ) frons dark green, densely punctate; palps, external surface of mandibles, labrum and clypeus dark green. Genae dark blue-green; there is no darker postocular stripe. In Nigerian specimens ( Fig. 21 ) and in the Cameroonian lectotype ( Fig. 19 ) frons and genae are, however, white. This may be another example of a geographic race, similar to that seen in P. inuncatus .

THORAX. Pronotum with 4 deep sulci, the posterior three crossing the disc. Cuticle inflated laterally between sulci 2 and 3. Cuticle anterior to 2 nd sulcus and posterior to 4 th sulcus pitted, but smooth between sulci 2 and 4. Metazona very narrow, only 1/16 length of prozona, its posterior margin almost straight, slightly embayed in the midline. Metathoracic tergite sparsely punctate, mesothoracic epimeron densely punctate, rest of thoracic pleura mostly smooth. Prosternal process cylindrical, erect, bluntly pointed. Wings and elytra absent, represented only by a faint wrinkle on the mesothoracic pleuron. All thoracic structures blue-black, except for the legs, which are green, and the hind knee and the condyle of the hind tibia, which are red. The pronotal metazona is a lighter blue than elsewhere and has a pair of ill-defined paler patches dorsolaterally.

ABDOMEN. Tergite of first abdominal segment sparsely punctate, dark blue-black with paler patches either side of the midline. Tympanum whitish. Tergites of second and third segments smooth and glossy, dark blue-black. Fourth segment yellowish. Fifth abdominal and all more distal segments red. Cerci cylindrical, tapering to an acute point, extending to the tip of the supraanal plate. Male 10 th abdominal tergite with either a small furcula or a medial tubercle, or an intermediate structure caused by a diminished separation between the furcula tips ( Fig. 24 ; see below under Taxonomic remarks).

THE PHALLIC COMPLEX ( Fig. 23 ). Broadly similar to that of all other members of the genus, but has a number of special features. The epiphallus ( Fig. 23A–D ) is unusually deeply sculptured; the bridge, seen dorsally, is bordered by a long continuous sclerotised lophal ridge along its posterior margin, extending from the central division to the tip of the lophus – there are no ‘peaked’ inner lophi, but instead a continuous sclerotized lophal ridge. The anterior edge of the bridge is also markedly raised; in combination with the lophal ridge this means that the lowest point on the bridge is the transverse midline, running between the two ridges. This structure causes difficulties in portrayal - in axial view the lower part of the lophal ridge tends to be obscured by the elevated anterior margin. The valvular plate is greatly developed and ornamented with longitudinal folds laterally and with an erect hood-like membranous fin dorsally ( Fig. 23E–G ). It is larger than in all other species of the genus. As in other spp., the endophallic valves are formed by relatively large ventral aedeagal sclerites adjoined to the spatulate endophallic processes.

Female

The female has not been described previously; it is appreciably larger than the male and can be strikingly different in colouration.We have deposited a female specimen (spec. no. 182023MII) in the MfN. Females are generally similar to the males in colouration, but in the Yabassi sample are predominantly green, not blue, with a red abdomen (see Fig. 22C ). Within the genus this sexual dimorphism in colouration is unique to this species. However, in a more easterly population in the Lobéké National Park the females are blue ( Fig. 22B ), like the males, so it appears that the dimorphism is confined to the females. Female terminalia as in generic description, but egg guide sculptured, laterally compressed, not cylindrical as in most species, sharply pointed, more than half the length of the ventral ovipositor valves.

Measurements

See Table 6 .

Remarks

The lectotype (see photograph, Fig. 19 ) was not available to us, so we cannot define the species by the lectotypic internal genitalia. Bolívar’s 1905 description of the male states that the specific name comes from the blue colouration of the head (this, however, is no longer visible on either the Madrid or the London specimens, though very striking in living males; see Figs 20 , 22 ). His description stresses that the last abdominal tergite has no furcula, unlike most species of the genus, but in its place a small medial tubercle ( Fig. 24A ) which is not bifid (he uses the Latin “ haud ” [by no means]), thus differing from impennis and finoti , both of which have a median process bifid at the tip, apparently derived by fusion of the furcula prongs.

The Nigerian specimens (NHMUK), two of which are illustrated in Fig. 21 , fit Bolívar’s description perfectly, though since collection they have lost all trace of blue colouration; they all have a medial tubercle, like the Cameroonian holotype. These specimens come from Cross River State and the former Akwa Ibom State, both situated on the SE coast of Nigeria, close or adjoining to Cameroon.

In Cameroon, we have recently collected new material in Littoral Division (from Djawara, near Edea, from Bonépoupa, and from Yabassi). There are five males; all have a medial tubercle on the last abdominal tergite as described by Bolívar, but contrary to Bolívar’s description the tubercle is clearly more or less bifid ( Fig. 24 ) and is obviously formed by the fusion of two processes presumed to be homologous with those forming a furcula in other species of the genus; in one Yabassi specimen (spec. no. 2021039, Fig. 24E ) the separation is enough to merit the structure being called a furcula, rather than a medial tubercle. The Nigerian specimens with a unitary tubercle and the Cameroonian specimens with a bifid tubercle differ in no other way, apart from the colour of their frons and genae. We have compared their phalli and found that they are identical and distinctive, unlike those of any other species. We conclude that the males of coeruleocephalus are variable with respect to the medial tubercle/furcula, and that this character as described by Bolívar is therefore not diagnostic of the species.

Apart from variation in the furcula, this species also shows more variation in colouration over its geographical range than usual in this genus: in addition to the polymorphism in body colour in the females, there are differences as described in the colour of genae and frons in different localities. However, the highly characteristic phallus seems to be invariant, suggesting that all these variations are intraspecific.

Distribution

Eastern and W Central Cameroon, SE Nigeria (Cross River State, Akwa Ibom State).

Status of taxonomic material

Adequate. Both sexes are now known, and modern localities. Adequate numbers of specimens present in museum collections.

Figures

Fig. 19. Pterotiltus coeruleocephalus Bolívar, 1905, lectotype, ♂ (MNCN_Ent 119720). A. Lateral view. B. Dorsal view. C. Labels (photos M. París, MNCN)

Fig. 20. Pterotiltus coeruleocephalus Bolívar, 1905, living males. A. W Cameroon, Littoral Division, Yabassi. B. E Cameroon, Lobéké Nat. Park. C. Nigeria, CRS, Ina River (photo Lincoln Fishpool).

Fig. 21. Pterotiltus coeruleocephalus Bolívar, 1905, males from Eastern Nigeria (ex NHMUK).A. Akwa Ibom State, Stubbs Creek F.R. (CIEA 20564). B–C. Cross River State, Calabar, nr Unget (CIEA 14152). These all have a medial tubercle on abdominal tergite 10, as described by Bolívar, rather than a furcula. It is clearly visible in C. Compare with Fig. 24A.

Fig. 22. Pterotiltus coeruleocephalus Bolívar, 1905, females. A. Lateral view of terminalia, showing the relatively short and sculptured egg guide below the ventral ovipositor valves. B–C. Living specimens. B. Cameroon, Lobéké National Park. Here, the females have the same predominantly blue colouration as the males. C. Cameroon, Yabassi. Here the females have a predominantly green ground colour,

Fig. 23. Pterotiltus coeruleocephalus Bolívar, 1905, phallic complex. It is noticeable for a) the large size and form of the valvular plate, with a prominent dorsal fin, and b) the sclerotized lophal ridge of the epiphallus. A–C. Epiphallus in dorsal (A), axial (B) and oblique dorsal (C) views. D. Intact phallus, fully extended, stained with acid fuchsin, perspective dorsolateral view. E. Intact phallus, extended, unstained, lateral view. F–G. Valvular plate dissected free, two different dorsal views. In G the edge of the dorsal fin has been digitally lightened for ease of visualisation. Abbreviations: see Material and methods. Scale in F = 1 mm.

Fig. 24. Pterotiltus coeruleocephalus Bolívar, 1905, male furcula. A. Lateral view of terminalia of holotype, showing in profile (arrowed) the medial tubercle described by Bolívar (photo M. París, MNCN). B–E. Dorsal views of medial area of tenth abdominal tergite in four different males from Yabassi, Cameroon, showing the variation in spacing of the furcular prongs. In E (specimen no 2021039) the prongs are distinctly separated, forming a true furcula, whereas B–D show different degrees of fusion of the prongs, in B resulting in a medial tubercle rather than a furcula.