Acrotylus incarnatus Krauss 1907

Acrotylus incarnatus Krauss, 1907 Figs 58, 59, 60, 61, 64, 65 References for Socotra. Burr 1898: 384 [as Acrotylus longipes]; Burr 1903: 412, 419 [as A. longipes]; Krauss 1907: 17, 19–20, 29 [as A. longipes var. incarnata]; Uvarov (in Uvarov and Popov (1957)): 378; Wranik 1998: 171; Wranik 2003: 324, plates 153, 157; Massa 2009: 56–57, figs 10, 13, 16; Hemp and Rowell 2020: 104; Wehrt 2021: 5–7 [as Acrotylus longipes]. Diagnostic notes. Acrotylus Fieber, 1853 is a genus of relatively small and slender Oedipodine grasshoppers characterised by a short, strongly saddle-shaped pronotum with a dark mark on the lateral lobe, with an off-central white dot (Figs 58 – 60, 62 – 65). Acrotylus incarnatus is slender, long-winged and - legged. The hind wings are basally orange-red without a dark band. The pronotum is smooth with a rounded posterior margin, a weak median carina, weak first and primary transverse sulci and a gently sloping first half of the prozona (Figs 58 – 60, 64 C, F). A. incarnatus resembles a second species of Acrotylus present on the island: A. innotatus (Figs 62 – 65). The latter species is as slender as A. incarnatus, but A. incarnatus has longer femora of the mid-legs (Fig. 65). The main differences are in the pronota (Fig. 64). A. innotatus has a step-like raised frontal half of the prozona in lateral view, a subrounded to slightly angular posterior margin and a rugose surface. Hind wings are pinkish-red basally instead of orange-red, like in A. incarnatus, although the difference can be subtle. The wings in A. innotatus are infumated in the apical half, with prominent black apical spots (Figs 63, 65 B), while A. incarnatus lacks this infumation. Taxonomic notes. Krauss (1907) based his description of A. longipes var. incarnata on specimens collected by Oscar Simony on Socotra in 1899 (Fig. 59), but also lists the specimen collected by Bennet (in 1896–1897) in the description. Therefore, the latter specimen, present in OUMNH, must be considered one of the syntypes. Krauss (1907) mentioned that the described var. incarnata is characterised by hind wings with a “ meat red ” coloured base, contrary to the nominate species in which the base of the hind wing is yellow. He further stated that the same var. occurs in Sicily (It.) and southern Tunisia. Uvarov (in Uvarov and Popov (1957)) raised Krauss’ var. incarnata to a full species. He stated that all Socotran specimens have rose-coloured wings and that A. longipes is more heavily built and appears “ specifically distinct ” from incarnatus. At the same time, he stated that the Socotran incarnatus “ do not differ morphologically ” from Acrotylus longipes var. meruensis Sjöstedt, 1932 from East Africa and synonymised the latter with the former. Massa (2009) raised var. meruensis to species level, based on differences in femur length and characteristics of the pronotum and, as a consequence, considered incarnatus a Socotra endemic. Preliminary results of genetic analyses by Wehrt (2021) suggest incarnatus to be a junior synonym of A. longipes. Until that research has been published more extensively, we here consider incarnatus a full species, as indicated by Uvarov (in Uvarov and Popov (1957)) and Massa (2009). Distribution and occurrence. A. incarnatus is endemic to Socotra. It is widespread and very common and one of the most numerous species of grasshoppers (Fig. 61). Despite its abundance and widespread distribution on Socotra, there are no known records from other islands in the Archipelago. Acrotylus longipes occurs in southern Europe, northern Africa, Central Asia and the Middle East, including Arabia. Habitat and biology. It is a geophilous species of sparsely vegetated, sandy and gravelly soils. Very common on sandy and gravelly plains along the coast, as on stony plateaus and vegetated meadows in the Hagher. Records are mainly from sparse dwarf and low Croton - Jatropha shrubland, submontane grassland and open areas within higher-elevation woodlands and forests. It occurs at elevations from 0–1000 m a. s. l. Records are from all seasons. Bioacoustics. Members of the Oedipodinae subfamily are known to emit quiet, buzzing sounds during rivalry, courtship and flight. From the genus Acrotylus, the sounds resemble the noise created by squabbling house sparrows, Passer domesticus (Roesti and Keist 2009). On Socotra, sounds have not been recorded.