A new species of Pterotiltus Karsch (Orthoptera, Acrididae, Oxyinae) from Equatorial Guinea

Materials and methods

Field sites.-Collections were made from 15 December 2023 to 19 December 2023 by H. Song, J.B. Linde, B.M. Woo, R. Mariño-Perez, and C. Oumarou-Ngoute on Bioko Island in Equatorial Guinea. The vegetation type in this part of Africa is humid forest (Zwets et al. 2024). Bioko Island (Fig. 1) is of volcanic origin; together with the Sao Tomé and Principe Islands, they are part of the Cameroon Volcanic Line. The altitude of the island ranges from 0 m (sea level) to 3,011 m.a.s.l. (Mount Pico Basile) (Elhag 2016). The climate is the Guinean type, with four seasons: two short dry seasons between two long rainy seasons. Rainfall varies from 3,500 mm in the highest parts of the mountain to less than 2,000 mm in the peneplains. The main plant groups are Fabaceae, Orchidaceae, and Poaceae (Velayos et al. 2013). In West-Central Africa, human activities such as logging and agriculture have progressively modified the natural environment. After deforestation, the ground is dominated by fallow-land plant species such as Acalypha arvensis, Chromolaena odorata, and Ageratum conizoides.

Morphological study.-Specimens were studied using a Wild stereo microscope. Drawings were made (under 12-50× magnification) using a camera lucida attached to the microscope and refined in Photoshop 2021 (Adobe Corp.). Macrophotographs were taken using an AmScope MU130 digital camera attached to the microscope. Other photographs were taken in the field with a Canon IXUS camera and in the laboratory with a Nikon D90 camera. The male phallic structures were extracted using conventional techniques from relaxed specimens and then macerated in 8% KOH, manually cleaned, neutralized in dilute acetic acid, and stained in acid fuchsin. The terminologies used for male genitalia description and the female subgenital plate and spermatheca are from Hollis (1971 and1975) and Randell (1963), respectively.

Measurements.-Measurements were made under the microscope using a graticule eyepiece and a digital stage (Mitutoyo) reading to 0.01 mm. The following measurements were made: P: length of the pronotum in the midline; L: overall length from the tip of the fastigium to the most posterior part of the genitalia, measured in lateral view; Ant: length of the antenna from the scape to the tip of the antenna; IOS: inter-ocular space, measured dorsally ; E-E: maximum width across the eyes measured dorsally; Fast-B, breadth of the fastigium measured from a dorsal view, between the inner edges of the two lateral ocelli; Fast-L, length of the fastigium measured from a dorsal view, anterior to the most anterior portion of the compound eyes; F: maximum length of the hind femur; FD: depth of femur measured as the distance between the two parallel lines running through the dorsal and ventral extremities of the femur, drawn parallel to the long axis of the femur; Ta1, Ta2, Ta3: lengths of each of the three hind tarsal segments; Sp Ext: number of external spines in the hind tibia; Sp Int: number of internal spines in the hind tibia. Measurements and ratios were given as the range of average ± standard error of individual measurements and were also presented after normalization [obtained by dividing the measured value by P (the length of the pronotum)]. The normalized values allowed for a comparison of species of different sizes. The foot formula shows the relative lengths of the three tarsal segments within the total length of the foot and again allows for comparison between different species (Rowell 2005). The foot formula values and the ratios describing sexual dimorphism (i.e., male/female) were calculated from the average values of the sample and not from individual measurements.

Abbreviation of depositories.-MfN Museum für Naturkunde, Berlin, Germany ONC Personal collection of C. Oumarou Ngoute, Cameroon RC Personal collection of C.H.F. Rowell, Switzerland Results Taxonomy Order ORTHOPTERA Olivier, 1789 Superfamily ACRIDOIDEA MacLeay, 1821 Family ACRIDIDAE MacLeay, 1821 Subfamily OXYINAE Brunner von Wattenwyl, 1893 Genus Pterotiltus Karsch, 1893 = Pygostolus Karsch, 1891 (syn. Karsch 1893) Type species.-Pterotiltus impennis (Karsh, 1891).

Subsequent literature. -Ramme 1929: 313. Johnston 1956: 258. Jago 1964: 190-204. Dirsh 1965: 579. Johnston 1968: 173. Dirsh 1970: 119. Hollis 1975: 226. Rowell 2005: 33-43. Oumarou-Ngoute and Rowell 2024: 127-146. Rowell and Oumarou-Ngoute 2025: 1-104. Generic diagnosis.-(Slightly modified from Rowell and Oumarou-Ngoute 2025 in terms of the shape of the ventral surface of female subgenital plate). Our modification: ventral surface of female subgenital plate flat, smoothly rounded, or with a medial groove in the posterior part, which is bounded laterally by two slightly inflated ridges not exceeding the posterior edge of the plate. See Rowell and Oumarou-Ngoute (2025) for the complete redescription and diagnosis of the genus. Pterotiltus bioko Oumarou-Ngoute & Rowell, sp. nov. https://zoobank.org/4E97F154-F283-4ACC-8795-5EE0E0D3F599 Material examined.-Holotype: EQUATORIAL GUINEA, Bioko Island • ♂; Road to Ureka, Reserva Cientifica de la Caldera de Luba, Bioko Island; 03°13'3"N, 008°21'4"E; altitude 1345 m; 15-xii-2023; H. Song, R. Mariño-Pérez, J.B. Linde, B.M. Woo, & C. Oumarou-Ngoute leg.; specimen N°. 8012023D; MfN. Paratype: EQUATORIAL GUINEA, Bioko Island • 1♀; Pico Basile National Park, Bioko Island; 03°23'20"N, 008°29'51"E; altitude 1374 m; 18 December 2023; H. Song, R. Mariño-Pérez, J.B. Linde, B.M. Woo, & C. Oumarou-Ngoute leg.; specimen N°. 7732023D; MfN. Other material examined.-EQUATORIAL GUINEA, Bioko Island; H. Song, R. Mariño-Pérez, J.B. Linde, B.M. Woo, & C. Oumarou-Ngoute leg. (36♂, 24♀) • 9♂; road to Ureka, Reserva Cientifica de la Caldera de Luba; 03°13'3"N, 008°21'4"E; altitude 1345 m; 15 December 2023; specimens N° 7972023D 7942023D 7962023D

7952023D 7992023D 7982023D 8002023D 8022023D 8032023D; ONC • 1♂; same information as previous; 03°12'57"N, 008°21'11"E; altitude 1370 m; specimen N° 8122023D; ONC • 2♂; same information as previous; 03°20'09"N, 008°35'07"E; altitude 1204 m; specimens N° 7852023D 7862023D; ONC • 9♂, same information as previous; 03°12'7"N, 008°21'4"E; altitude 1192 m; specimens N° 8452023D 8312023D 8332023D 8342023D 8372023D 8322023D 8362023D 8352023D 8462023D; ONC • 3♀; same information as previous; 03°13'3"N, 008°21'4"E; altitude 1345 m; specimens N° 7932023D 7892023D 7902023D; ONC • 3♀; same information as previous; 03°20'09"N, 008°35'07"E; altitude 1204 m; specimens N° 7792023D 7812023D 7832023D; ONC • 10♀; same information as previous; 03°12'7"N, 008°21'4"E; altitude 1192 m; specimens N° 8302023D 8292023D 8222023D 8212023D 8242023D 8272023D 8282023D 8232023D 8252023D 8262023D; ONC • 1♂; same information as previous;, , 03°13'3"N, 008°21'4"E; altitude 1345 m, specimen N° 8382023D; RC • 3♂: Pico Basile National Park, 03°38'53"N, 008°49'45"E; altitude 1374 m; 18 December 2023; specimens N° 7702023D 7712023D 7722023D; ONC • 7♂; Lago Biao, Reserva Cientifica de la Caldera de Luba; 03°21'20"N, 008°37'17"E; altitude 1831 m; 16 December 2023; specimens N° 8082023D 8092023D 8112023D 8072023D 8052023D 8062023D 8042023D; ONC • 2♂; same information as previous; 03°13'3"N, 008°21'4"E; altitude 1345 m ; specimens N° 7842023D 7802023D; RC • 3♀; Pico Basile National Park; 03°38'53"N, 008°49'45"E; altitude 1374 m; 18 December 2023; specimens N° 7742023D 7752023D 7762023D; ONC • 5♀; same information as previous; 03°22'33"N, 008°28'48"E; altitude 1864 m; N° 8392023D 8402023D 8432023D 8422023D 8442023D; ONC • 1♂; same information as previous; ; 03°38'53"N, 008°49'45"E; altitude 1374 m; 18 December 2023; specimen N° 7692023D; ONC • 1♂; Lago Biao, Reserva Cientifica de la Caldera de Luba; 03°21'20"N, 008°37'17"E; altitude 1831 m ; 16 December 2023; specimen N° 8102023D; RC.

Type locality.-Reserva Cientifica de la Caldera de Luba, Bioko Island, EQUATORIAL GUINEA.

Etymology.-Toponymic, referring to Bioko Island, Equatorial Guinea.

Description.-(Figs 123456, Tables 1, 2). Male. Body of small size, average length of body 14.22 mm (Table 1); fastigium of vertex rounded or roughly pentagonal in dorsal view with a medial carina, its tip merging smoothly with frontal ridge. Frons slightly oblique; frontal ridge shallowly sulcate above medial ocelli, obliterated below; antennae longer than the combined length of head and pronotum together; eyes protuberant, inter-ocular space slightly wider than antennae scape. Pronotum dorsally crossed by three deep sulci; medial carina very weak or absent. Space between sulci 2 and 3 almost equal to or slightly wider than metazona in length; metazona short, accounting for less than 25% of the pronotum length (Fig. 3A). Lateral margins of prozona tuberculate in dorsal view, anterior margin of prozona slightly convex, sometimes slightly notched in the midline. Posterior margin of metazona slightly convex and notched in the midline; prosternal process conical, vertical, pointed. Mesosternal space slightly longer than wide, lobes rounded; metasternal space open, about half of mesosternal space; micropterous. Tegmina minute, lobiform, shorter than, reaching, or barely exceeding middle of metathorax but not reaching mesothorax (Fig. 3B). Hind femur slender, 5 times longer than wide (Table 1); 6 to 7 external tibial spines, 8 to 9 internal tibial spines (Table 1), external apical spine present; paired internal tibial spurs longer than external spurs. Tympanum wide, oval or rounded. Last abdominal tergite divided, the hind margin with two small lobiform processes forming a minute furcula, the tips separated by 0.3-0.35 mm (Fig. 3D, E), cercus compressed laterally, slightly incurved, slightly shorter than or exceeding the tip of the subgenital plate, with acute apex. Supra-anal plate triangular in dorsal view with acute or slightly rounded apex; proximally in the plate there is a short medial longitudinal groove bounded posteriorly by a curved transverse ridge that extends across the width of the plate (Fig. 3D). Phallic complex (Figs 4A, B, 5A, B) of large size for the genus, ectophallic membrane coarsely stippled and obscures most of the sclerites; epiphallus with large forwardly curved blade-like outer lophi; inner lophi absent (Figs 4C, D, 5C, D). Anterior processes of epiphallus well developed, axially large and rounded, ancorae absent (Figs 4C, D, 5C, D). Oval sclerites large with pronounced pointed tubercles on their ventral surfaces (Fig. 4F); valvular plate foliose, showing large lobes that dorsally join the cingulum by a well-prolonged arch. Cingular apodemes dorsally blade-like, incurved (Fig. 5E); cingular ramus laterally large, prolonged and rounded (Fig. 5F). Endophallic apodemes dorsally slender, laterally large, spatula shaped, with robust, long and pointed gonopore processes; endophallic process terminates on the ventral aedeagal sclerite which forms a part of the ventral aedeagal valve (Fig. 5G).

Female. In general, similar to the male. Female particularities: body of small to medium size, average L = 18.11 mm (Table 1). Lateral margins of prozona less tuberculate in dorsal view; last abdominal tergite short, divided, but the hind margin without a furcula. Cercus robust, very slightly compressed laterally almost Table 1. Measurements of Pterotiltus bioko sp. nov. P: length of the pronotum in the midline; L: overall length from the tip of the fastigium to the most posterior part of the genitalia, measured in lateral view; Ant: length of antenna from the scape to the tip of antenna; IOS: interocular space measured dorsally; E-E: maximum width across the eyes measured dorsally; Fast-B: breadth of fastigium measured in dorsal view between the inner edges of the 2 lateral ocelli; Fast-L: length of fastigium, measured in dorsal view anterior to the most anterior portion of the compound eyes; F: maximum length of the hind femur; FD: depth of femur measured as the distance between the two parallel lines running through the dorsal and ventral extremities of the femur drawn parallel to the long axis of the femur; Ta1, Ta2, Ta3: lengths of each of the three hind tarsal segments; Sp Ext: number of external spines in the hind tibia; Sp Int: number of internal spines in the hind tibia. The foot formula shows relative lengths of the three tarsal segments to the total length of the foot.

Male Dimensions in mm P L Ant IOS E-E Fast-B Fast-L F FD Ta1 Ta2 Ta3 Ta1-3 External spines Internal spines Minimum 2.68 12.75 7.35 0.34 2.70 0.79 0.45 8.04 1.84 0.93 0.48 1.09 2.51 6 8 Maximum 3.36 15.87 10.35 0.52 3.47 1.17 0.85 10.61 3.13 1.51 0.86 2.02 4.09 7 9 Average 2.98 14.22 9.09 0.43 3.23 0.98 0.61 9.88 2.09 1.23 0.63 1.73 3.60 Median 7 8 Standard error 0.03 0.12 0.15 0.01 0.01 0.01 0.01 0.11 0.03 0.02 0.01 0.02 0.06 N 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 Foot formula 34% 18% 48% Ratios L/P Ant/P IOS/P E-E/P Fast-B/P Fast-L/P F/P FD/P Ta1/P Ta2/P Ta3/P Ta1-3/P F/FD Ta1-3/F Minimum 4.07 2.39 0.10 0.96 0.25 0.14 2.92 0.63 0.33 0.15 0.39 0.89 2.93 0.29 Maximum 5.27 3.57 0.17 1.20 0.43 0.30 3.79 0.99 0.48 0.28 0.69 1.37 5.27 0.40 Average 4.78 3.05 0.14 1.08 0.33 0.20 3.32 0.70 0.41 0.21 0.58 1.21 4.76 0.36 Standard error 0.05 0.05 0.01 0.01 0.01 0.01 0.03 0.01 0.01 0.01 0.01 0.01 0.07 0.01 N 31 31 31 31 31 31 31 31 31 31 31 31 31 Female Dimensions in mm P L Ant IOS E-E Fast-B Fast-L F FD Ta1 Ta2 Ta3 Ta1-3 External spines Internal spines Minimum 2.99 15.09 7.82 0.46 3.25 1.06 0.56 10.61 2.06 1.24 0.49 1.81 3.69 6 8 Maximum 3.99 20.24 10.24 0.93 4.05 1.56 0.98 13.45 2.93 1.89 0.98 2.60 5.33 7 9 Average 3.61 18.11 8.99 0.63 3.75 1.34 0.76 12.26 2.56 1.57 0.82 2.18 4.59 Median 7 9 Standard error 0.05 0.29 0.17 0.02 0.04 0.02 0.01 0.01 0.03 0.03 0.02 0.04 0.19 N 24 19 24 24 24 24 24 24 24 24 24 24 24 24 24 Foot formula 34% 18% 48% Ratios L/P Ant/P IOS/P E-E/P Fast-B/P Fast-L/P F/P FD/P Ta1/P Ta2/P Ta3/P Ta1-3/P F/FD Ta1-3/F Minimum 4.47 2.14 0.12 0.93 0.27 0.14 2.99 0.62 0.34 0.16 0.50 1.03 4.38 0.32 Maximum 5.50 2.66 0.25 1.15 0.42 0.25 3.95 0.86 0.51 0.28 0.68 1.44 5.16 0.40 Average 5.01 2.47 0.17 1.04 0.37 0.21 3.39 0.70 0.43 0.22 0.60 1.27 4.79 0.37 Standard error 0.05 0.03 0.01 0.01 0.01 0.01 0.04 0.01 0.01 0.01 0.01 0.01 0.04 0.01 N 24 19 24 24 24 24 24 24 24 24 24 24 24 Sexual dimorphism Dimensions in mm P L Ant IOS E-E Fast-B Fast-L F FD Ta1 Ta2 Ta3 Ta1-3 External spines Internal spines Male/female Averages (or Medians) 0.82 0.78 0.98 0.68 0.86 0.73 0.80 0.80 0.81 0.78 0.76 0.79 0.78 1 0.88 Normalized on 82% 1 0.95 1.19 0.82 1.04 0.89 0.97 0.97 0.98 0.95 0.92 0.96 0.95 Male/female Ratios 0.95 1.23 0.82 1.03 0.89 0.95 0.97 1 0.95 0.95 0.96 0.95 conical, straight or very slightly excurved, equaling or slightly exceeding the supra-anal plate, with acute apex; supra-anal plate triangular in dorsal view, elongated, lingulate, with rounded apex.

Ovipositor valves smooth, slender, long, with rounded apex; subgenital plate ventrally conical, distally with a medial groove bounded laterally by two inflated ridges, not projecting posteriorly beyond the posterior edge of the plate. Egg-guide slender, rod-like, long, about half of the ventral ovipositor valves in length (Fig. 3C). Dorsally, subgenital plate smoothly triangular, terminated by a straight and pointed egg guide at the tip; a pair of large sclerotized columellae that are prolonged by a pair of less sclerotized stripes (Fig. 6A). Bursa copulatrix large, dorsally with a longitudinal groove separating the bursa into two somewhat distinct lobes (Fig. 6B, C), spermathecal duct long; spermatheca with a hooked terminal ampulla and a developed lateral diverticulum (Fig. 6B, D). Sexual dimorphism.-(Table 1) The average length of pronotum (P) of males is 82% of that of females. The male antennae are longer than those of females (after normalization, the ratio of male/female Ant = 1.23). In the males, the interocular space (IOS) is smaller than in the females (male/female IOS = 0.68, and 0.82 after normalization). Breadth of fastigium (Fast-B) is slightly shorter in males than in females (male/female Fast-B = 0.73, and 0.89 after normalization). There are generally less internal tibial spines in males than in females (male/female medians = 0.82) (Table 1). After normalization, the ratios of the various other body dimensions are closely similar in both sexes (Table 1).

Coloration.-(Fig. 2A-F). Male. Body multicolored, predominantly black; scape and pedicel of antennae light green. First two or three segments of flagellum green, tip white or light green, the remaining segments brown. Fastigium of vertex green or greenblack; vertex black, eyes black fading to brown when dried. Frons yellow-white; genae black in upper half and yellow-white or yellow in inferior half; clypeus, labrum, and palps green with whiter mottling. Pronotal disc black with a wide yellow patch at the anterior margin of prozona; metazona dorsally yellow; tegmina yellow; mesothoracic and metathoracic tergites black. Pronotal lobes black with two yellow patches, one in the antero-basal edge joining the yellow tripe of the genae, another at the postero-basal edge behind the third sulci of pronotum (in some specimens, the last yellow patch can join dorsally the yellow metazona to form a single stripe). Prosternum, mesosternum, and metasternum light-green; fore and middle femora orange-green, tibiae and tarsi orange-green fading green-brown or brown when dried. Hind femora orange-green; hind knee brown, upper lobes of hind knee brown, lower lobes brown-green. Hind tibiae and tarsi light green with black spines; tergite of first abdominal segment black, with paired yellow patches at the posterior margin; tergites 2 and 3 black; tergite 4 yellow-green or green or orange-green; all other abdominal segments green or orange-green. Female. We observed two different female morphotypes: All are green but some (the majority) have red patches in pronotal lobes (Fig. 2C), the rest have yellow patches. The yellow-patched females looked newly molted (Fig. 2D), suggesting that the color difference is developmental and that mature females are all red. Body multicolored, predominantly green, fading brown when dried. Scape and pedicel of antennae green; flagellum brown with white or light brown tip. Fastigium of vertex and vertex green; eyes black fading to light yellow or brown when dried. Frons green, clypeus, labrum, and palps green. Genae green with a red or yellow stripe, narrow below eyes, widened toward the pronotal lobes, and continuous in two patches in the pronotal lobes. Pronotum disc green; tegmina yellow; mesothorax and metathorax green, prosternum, mesoternum, and metasternum yellow-green or light-green. Fore and middle femora proximally yellow-green or orange-green; distally light-green. Tibiae and tarsi light-green; hind femora externally green, internally yellow-green or orange-green. Hind knee brown; hind tibiae and tarsi green with black spines. All abdominal segments green.

Diagnosis.-Of small size relative to the rest of the genus, with average L = 14.22 mm in male and L = 18.11 mm in female. Body predominantly black in male with wide yellow patches in pronotum, female genae green with a red or yellow stripe, narrow below eyes, widened toward the pronotal lobes, and continuous in two patches in the pronotal lobes, abdominal segments green (Table 2); different to P. apicalis (Fig. 7). Metazona short, accounting for less than 25% of the pronotum length; tegmina minute, lobiform, shorter than, reaching, or barely exceeding the middle of the metathorax but not reaching the mesothorax. Furcula small, lobiform, the tips separated by 0.3-0.35 mm. Oval sclerites of epiphallus large, with pronounced pointed tubercles on their ventral surfaces; endophallic apodemes dorsally slender, laterally large, spatula shaped, with robust, long, and pointed gonopore processes; pronounced flexure (Table 2).