Bioacoustics of Arantia (Euarantia) rectifolia

Remarks . The subgenus Euarantia was established by Heller et al . (2014) on the base of the width of the tegmina being greater than 12 mm and the hind tibiae curved; however, A. rectifolia Brunner von Wattenwyl, 1878 , considered to belong to the subgenus Euarantia , has the hind tibiae curved but the width of the tegmina is variable in size, sometimes being shorter than 12 mm , often mixing with A. marginata Massa, 2021 (belonging to the subgenus Arantia ) from which the morphological separation may be difficult (however, the shape of male cerci and stridulatory file allow for the distinction). In the group of A. rectifolia morphological differences generally are small, but the shape of the stridulatory file and the number of teeth, as well as the male cerci tip, allowed Hemp & Massa (2017) to describe Arantia tanzanica (ca. 80–85 teeth; Figs. 15a, 15b ), found in Zimbabwe , Mozambique , South Africa , Swaziland and Zambia ( Massa 2022a ). Massa (2021b) highlighted the difficulty in identifying Arantia rectifolia from A. marginata and a possible third species which is sometimes mixed between them, recognizable only by its stridulatory file (ca. 85 teeth, like in A. tanzanica while in A. marginata there are ca. 65 teeth, and in A. rectifolia ca. 45–50). Fig. 15 reports five stridulatory files and cerci of the respective specimens from Tanzania ( Arantia tanzanica ) ( Figs. 15a, 15b ), Côte d’Ivoire ( Arantia aff. tanzanica ) ( Figs. 15c, 15d ), Gabon ( Arantia marginata ) ( Figs. 15e, 15f ), Central African Republic ( Arantia rectifolia ) ( Figs. 15g , 15h ) and Côte d’Ivoire ( Arantia aff. rectifolia ) ( Figs. 15k, 15i ; this specimen, due to the width of the tegmina being shorter than 12 mm was considered as being Arantia aff. marginata by Massa 2021b ). It is possible that the specimens of Figs. 15g , 15h, 15k, 15i represent two species belonging to the rectifolia -group. A biomolecular analysis probably could answer this question, but the actual knowledge of taxonomy of this group of Arantia allows A. rectifolia , as well as A. tanzanica , to be moved from the subgenus Euarantia Heller, 2014 to the subgenus Arantia Stål, 1874 ; thus, their nomenclature should be changed as follows: Arantia ( Arantia ) rectifolia Brunner von Wattenwyl, 1878 , and Arantia ( Arantia ) tanzanica Hemp & Massa, 2017 .

Measurements . Males. Body length: 26.8–30.0 (mean: 27.0); pronotum length: 5.9–6.5 (mean: 6.2); pronotum height: 6.7–7.1 (mean: 6.9); hind femur: 25.5–28.5 (mean: 27.0); hind tibia: 27.1–30.1 (mean: 28.5); tegmina length: 45.0–49.0 (mean: 47.5); tegmina width: 12.0–13.8 (mean: 12.8); length/tegmina width: 3.5–3.7; width tegmina/length pronotum: 2.0–2.1. Measurements of the female holotype A . accrana . Body length: 24 mm ; pronotum length: 7 mm ; tegmina: 53 mm ; tegmina width: 12.8; hind femur length: 28 mm ; ovipositor: 5 mm ( Karsch 1889 ). Characters . A . rectifolia is a species of medium size [body length ♂ 26–30 mm ; ♀ 27–32 mm ; the size of the ♀ ( 47 mm ) reported by Griffini (1908) is uncertain, because doubtfully identified]. Brunner von Wattenwyl (1878) described the male and considered it similar to A . fatidica . Later, both sexes were recorded by Karsch (1889) , Brunner von Wattenwyl (1891) and Bruner (1920) from Lolodorf ( Cameroon ) and the Democratic Republic Congo . Ragge & Roy (1965) reported the species from Senegal , Ragge (1968b) from the Ivory Coast , and doubtfully Griffini (1908) from Mukonje Farm ( Cameroon ). Ebner (1943) recorded it again from Fernando Póo ( Equatorial Guinea ). The width of tegmina of the holotype is 12.8 mm , intermediate between Arantia and Euarantia , in other specimens examined it ranged between 12.0 to 13.8 mm . Hind tibiae are not as curved as it was given by Heller et al . (2014) for Euarantia . Typical is an ivory-coloured coating mixed with some dark traces on the fore tibiae in the area of the tympana. The dorsal sides of the tympana are conchate while the ventral sides are oval and open. The tegmina are not very broad, with sometimes only faintly visible 4–5 ivory (in living specimens) or more tawny to orange spots (in preserved specimens, see Figs 19 , 21, 22 ). The stridulatory file is short, curved and consists of 80–85 teeth ( Fig. 57 ). The fore femora are unarmed or armed with 1–2 small spines ventrally. The hind femora are armed with 3–5 inner and 4–7 outer ventral black-tipped or black small spines. Male cerci are long and slightly sinuous and have a black, chitinous and rounded apex ( Figs 88a, 88b ). Subgenital plate with tiny styli, in many specimens absent. Only the female of A . accrana was described by Karsch (1889) although 2 males are also present in the Berlin collection which Karsch himself identified as belonging to A . accrana in 1894 (examined; see Fig. 22 ). The comparison of material of the male holotype of A . rectifolia with the male identified by Karsch as A . accrana showed no differences between the two taxa. Also the female holotype of A . accrana was compared with females caught together with male A . rectifolia . No differences in size and shape of the ovipositor and subgenital plate could be detected. Brunner von Wattenwyl (1891) separated the taxa on base of the ventral spination of the fore femora (absent in accrana , present in rectifolia ) and the presence of ivory spots on the anterior margin of the tegmina. The ivory spots are expressed mostly in males and also the spination varies between specimens checked from being tiny to absent. At that time only the female of A . accrana was described and stored in Berlin and the key of Brunner of Wattenwyl was based on Karsch´s description. For these reasons here A . accrana is considered synonymous with A . rectifolia .