Physemophorus sokotranus ( Burr, 1898 )

Physemophorus sokotranus ( Burr, 1898)

Figs 118 View Figure 118 , 119 View Figure 119 , 120 View Figure 120 , 121 View Figure 121 , 122 View Figure 122

References for Socotra.

Burr 1898: 384–385, plate XXX, fig. 4 [as Poecilocerus sokotranus ]; Krauss 1900: 155–157, figs 1–4 [as Poecilocerus socotranus (sic)]; Burr 1903: 412, 419–420 [as Poecilocerus sokotranus ]; Bolívar 1904: 434 [as Poecilocerus sokotranus ]; Krauss 1907: 17, 21–23, 29, plate II: fig. 5 [as Physemophorus socotranus (sic)]; Popov (in Uvarov and Popov (1957)): 371 [as Physemophorus socotranus (sic)]; Kevan 1973: 1169; Popov 1997: 143–145, figs 73, 74; Wranik 1998: 171 [as Physemophorus socotranus (sic)]; Wranik 2003: 320, plates 150, 154.

Diagnostic notes.

Physemophorus sokotranus is a unique and beautifully, but subtly coloured grasshopper with soft tones of greyish-green, olive-green, reddish-brown and black (Fig. 118 View Figure 118 ). The most peculiar characteristic of this species is the knob-like tubercle on the dorsal side of the first tergite (Figs 119 View Figure 119 , 122 View Figure 122 ). It measures 1 mm in diameter, is present in males and females and is visible with closed wings because of a bend in the hind margin of both tegmina. Erroneously, Burr (1898) considered the pale hard knob-like tubercle as a “ foreign body, possibly a fungus ” and, therefore, omitted it from the species description. Krauss (1900, 1907) tried to explain the function of this tubercle, but failed and suggested it could be a light-emitting organ. Popov (1997) mentioned that the function is still unknown and that at least there is no such thing as a discharge of any substances in live specimens.

Taxonomic notes.

According to Burr (1898), the description of Physemophorus sokotranus is based on two females (№ 87, 88). The specimen in OUMNH (Oxford) (labelled as type № 87) was re-assigned as Lectotype by Kevan in 1958 (Fig. 119 View Figure 119 ). Specimens in NHMUK are erroneously labelled as types (note by Kevan) since they were collected in 1899, a year later than the species description ( Burr 1898).

Krauss (1907) erected the new genus Physemophorus , positioned between Poecilocerum and Zonocerus , but belonging within the Poecilocerum group, based on some unique characteristics like the dull colour, the short, thin legs and, above all, the knob-like tubercle on the dorsal side of the first tergite. Kevan (1973) considered the species of Zonocerus , common in East Africa, as the nearest, though distant relatives of Physemophorus . Popov (1997) placed the genus in the tribe Phymateini and subtribe Zonocerina , together with the genus Zonocerus .

Distribution and occurrence.

Physemophorus sokotranus is endemic to Socotra. It is considered common by Burr (1903) and Popov (in Uvarov and Popov (1957)). It is widespread in the island’s eastern half and common in the Hagher and locally on Dixam (e. g. Wadi Zerig). There are few records from the east part of the island, Homhil and Hamadero. One record is from Noged Plain on the southern shore and there is currently one western record from near Qalansiyah (Fig. 120 View Figure 120 ).

Habitat and biology.

The species is found in various vegetated habitats at elevations from 10–1200 m a. s. l.: on gravelly ground, rocks, trunks of trees and within herbs and shrubs. Popov (in Uvarov and Popov (1957)) explicitly mentioned Buxus hildebrandtii . In 2009 and 2010, specimens were found in Senna socotrana and on stems and branches of Croton socotranus (Figs 121 View Figure 121 , 122 View Figure 122 ). Popov (1997) suggested that the species is univoltine, based on sightings of adults and older nymphs in January – March and young nymphs in August.