Ruspolia basiguttata Schulthess 1898

Ruspolia aff. R. basiguttata (Bolívar, 1906) Figs 203, 204, 205, 206, 207 References for Socotra. Uvarov (in Uvarov and Popov (1957)): 364 [Homorocoryphus nitidulus]; Popov 1981: 128–130, figs 35–38; Wranik 2003: 314–315, plate 148. Diagnostic notes. Ruspolia aff. R. basiguttata is a large conehead unlikely to be confused with any other bush-cricket in Socotra. Most members of the species-rich tribe Copiphorini are acoustically distinct, but morphologically very similar: medium-sized to large bush-crickets with a large, pointed head and long wings reaching far beyond the hind knees. R. aff. R. basiguttata is the only large conehead species of the Archipelago. It occurs in both green and brown forms, similar to most species in the subfamily Conocephalinae. Taxonomic notes. Popov and Bailey tentatively identified material from Yemen, Oman and Socotra as possibly belonging to R. basiguttata, using Bailey’s key (1975) (Popov 1981) (Fig. 204). There are some marked differences, however, between R. basiguttata from Ghana and Cameroon and the Arabian and Socotran specimens: the latter have a smaller size, a higher number of teeth in the stridulatory file and a much weaker armature of the hind femur and knee (Popov 1981). The song resembles that of R. differens (Serville, 1838) (KG Heller, in litt.) (see Bioaccoustics). Further study is required to determine the specific status of the Socotran specimens. The genus Ruspolia Schulthess, 1898 requires a complete revision, combining morphological, molecular and bioacoustic data (Naskrecki and Guta 2019). Distribution and occurrence. R. basiguttata is only known from its type localities in Cameroon and Ghana (Naskrecki 2009). On Socotra, Ruspolia aff. R. basiguttata is restricted to the Hagher and Dixam Plateau (Fig. 205). Habitat and biology. In 2010, some males sang from deep inside shrubs of Searsia thyrsiflora at Adho Dimello resulting in us being unable to catch them (Fig. 206). The species occurs from 450–1000 m a. s. l. Older records are from Frankincense and Dracaena woodland and forests at lower elevations. Adults were recorded in January, March and October; nymphs in February and October. Bioacoustics. The calling song of Ruspolia aff. R. basiguttata is a continuous echeme, sometimes mixed with very short silences (200 ms) (Fig. 207), typical for all African species of the genus (Bailey 1975). Echemes consist of equal syllables, repeated at 150 per second (SRR). The carrier frequency of the song is around 13–15 kHz and has no clear harmonics at higher frequencies. Close inspection of the spectrogram shows that the opening and closing movements of the wings produce different carrier frequencies. Based on the high syllable repetition rate (SRR) of nearly 150 Hz, the Socotran species could be related to R. differens (KG Heller, in litt.). R. differens has the highest SRR of the African species of 120–160 Hz and a peak frequency between 13 and 17 kHz (Bailey 1975). Heller (2019) recorded an SRR of 189 Hz and a peak at 14 kHz during a high nightly temperature of about 28 ° C. Temperatures at Adho Dimello were not noted, but certainly much lower at the time of the sound recording in 2010 (Fig. 207). Hence, a much lower SRR is expected under such circumstances.