Oxytruxalis ensis (Burr, 1899)

Felix, Rob, Bouwman, Jaap, Odé, Baudewijn, Ketelaar, Robert, Pham, Duc Minh & Bailey, James, 2025, The grasshoppers and crickets (Orthoptera) of the Socotra Archipelago (Yemen): a comprehensive overview and a description of a new Oecanthus Tree Cricket (Oecanthidae), Contributions to Entomology 75 (1), pp. 21-166 : 21-166

Oxytruxalis ensis (Burr, 1899)

Figs 16 , 17 , 18

References for Socotra.

Burr 1899 b: 43–44 [as Truxalis ensis ]; Burr 1902: 161–162 [as Acrida ensis ]; Burr 1903: 412, 413, 416, plate XXV: figs 4, 4 a [as Truxalis ensis ]; Krauss 1907: 29 [as Acrida ensis ]; Dirsh 1950: 149–151, figs 50, 51; Popov (in Uvarov and Popov (1957)): 384–385; Wranik 2003: 325, plates 153, 158.

Diagnostic notes.

Oxytruxalis ensis is a very slender and elongated species (Figs 16 , 17 ). It differs from Truxalis viridifasciata (Fig. 19 ) in very long antennae that exceed the combined length of the head and pronotum, an almost flat and strongly elongated pronotum parallel in the prozona, very long tegmina that are gradually narrowed and pointed in the apical half and hind wings that are much shorter than the tegmina (Figs 16 , 17 ) ( Burr (1899 b, 1902, 1903). The inner upper lateral lobe of the hind knee is elongated and longer than the outer upper lobe (Fig. 17 B ) ( Dirsh 1950; Popov in Uvarov and Popov (1957)).

Taxonomic notes.

Burr (1899 b, 1903) described the species, based on two female syntypes (Fig. 17 ). Dirsh (1950) gave a re-description of the genus and species. The male of O. ensis has never been described. A short description of the male is provided here, together with a photo of the only known adult male specimen (Fig. 16 ).

Description of the male.

Smaller than the female; body length: 39 mm; frons 10 mm; antenna length: 18 mm; tegmen length: 26 mm; hind wing length: 23 mm. The apex of the fastigium tapers more sharply and is less rounded than in the female. The hind wing is relatively longer than in the female: it is only 12 % shorter than the tegmen; in females, this is 20 % (Figs 16 , 17 A ) ( Dirsh 1950). The pronotum is malformed, making it indescribable in detail. The subgenital plate is short and conical with a sharp apex. The general colouration is yellowish-green. The tegmina have longitudinal reddish, brownish and white lines. The basal disc of the hind wing is reddish with a tessellate pattern (Fig. 16 ). Other characteristics are the same as in the female (see Dirsh (1950)).

Distribution and occurrence.

Oxytruxalis ensis is endemic to Socotra and a very scarce species. It is only known from one adult male, two adult females and a nymph found in the mid-elevations in the Hagher massif and on the surrounding limestone plateau (Fig. 18 ). There are no records after 1967.

Habitat and biology.

The habitat is unknown. Based on its distribution, the species probably inhabits herbaceous or grassy sites in wood- and shrubland at 250–950 m a. s. l. All known localities, Moukaradia Pass, Wadi Dineghen and Jena-agahan, are in Frankincense woodland. Records are from January, March (a nymph), April and December.

Bioacoustics.

It is unknown if this species emits a calling song. Members of Truxalini are known to possess a stridulatory apparatus and can produce sounds through crepitation by snapping their hind wings during flight ( Harz 1975; Haggag and Badawy 2017).

Figures

Figure 16. Oxytruxalis ensis (Burr, 1899), male. The only known male specimen collected by Kenneth Guichard at Wadi Dineghen in April 1967. Scale bar: 1 cm (photograph Rob Felix).

Figure 17. Oxytruxalis ensis (Burr, 1899), female, holotype. A, D. Habitus; B. Left hind knee with elongated inner upper lobe; C. Label. Collected by Forbes & Ogilvie-Grant at Moukaradia Pass, Rooget Hill, Socotra in 1898. Scale bar: 1 cm (photograph T. Hunter, WML, Liverpool).

Figure 18. Distribution of Oxytruxalis ensis (Burr, 1899) in the Socotra Archipelago.

Figure 19. Truxalis viridifasciata (Krauss, 1902), female, holotype. Collected by Oscar Simony in 1899. Scale bar: 1 cm (photograph Harald Bruckner, NOaS Image Collection, Natural History Museum Vienna).