Bioacoustics of Isopsera arcuata

Description. Fastigium verticis widening anteriorly, ca 0.90 mm wide and widens slightly towards the frons; dorsal surface shallowly sulcate and separated from fastigium frontis . Pronotum lateral margins rounded; in dorsal view disc flat, very slightly widening paranota 1.1–1.2 times higher than long, ventral margin rounded, humeral sinus weak. Mesosternal lobes triangular, metasternal lobes rounded. Tegmina surpassing hind knees, translucent; PLATE I. Isopsera arcautus sp. nov. Male 1–6: 1. Dorsal view of head; 2. Dorsal view of fastigium vertices; 3. Dorsal view of pronotum; 4. Lateral view of pronotum; 5. Pro, meso and metasternum; 6. Stridulatory file on left tegmen. PLATE II. Isopsera arcautus sp. nov. Male 7–12: 7. Ventral view of sub-genital plate; 8. Genitalia—ventro-lateral view; 9. Tenth abdominal tergite with cerci; 10. Dorsal view—Left cerci; 11. Apex of cerci; 12. Apical spines of hind tibia. radial and medial field with regular parallel transverse veinlets, less regular costal field and with a network of irregular veinlets; radius sector branching before middle of tegmina simply furcated; dorsal field flat, acute triangular, stridulatory vein slightly protruding; stridulatory file elevated on a ridge, with large pegs over the entire length. Coxal spine on foreleg present, anterior tibiae dorsally furrowed, tympana open on both sides. Genicular lobes of pro- and meso-femora with minute internal and external spines positioned ventrad. Hind knees with bispinose internal and external ventral lobes. Male: Stridulatory file on the underside of left tegmina with about 90 large teeth widely spaced and many closed spaced teeth in the anterior part. Hind wings longer than tegmina ( 5.85 mm ).Tenth abdominal tergite large, apex slightly concave in middle. Cerci moderately curved and narrowing apically, with a row of teeth on the outer side and serrated internally; the apex curved, beak-like. Sub-genital plate broad at base narrowing towards apex with styli longer than length of sub-genital plate, styli somewhat cylindrical. Supra-anal plate tongue-shaped. Anterior femora without internal spines, but with 3–3 external spines; meso-femora without internal, but with 3–5 external spines; posterior femora with 5–7 external and 3–5 internal spines. Hind femora gradually swollen towards the base and suddenly thin at apex. Hind knee with internal and external lobes bispinose ventrally. Anterior tibia with 3–3 internal and 3–4 external spines, with 3 apical spines (dorsal external spine absent); meso-tibia with 5–6 internal and 6–7 external spines, and 3 apical spines(dorsal external spine absent); posterior tibia with 26–28 dorsointernal, 22–24 dorso-external, 10–12 ventro-internal and 17–19 ventro-external spines, besides the 6 apical spines (3 pairs).

Discussion. This species differs from I . spinosa and I . caligula on the basis of the shape and structure of the male cerci, stridulatory file and the subgenital plate. The new species morphologically appears similar to Isopsera caligula Ingrisch, 1990 ; but differs in the structure of the stridulatory file on left tegmen with respect to the number of teeth, the apex of cerci possessing teeth externally and serrated margin internally; the 10th abdominal tergite is not pilose as I . caligula ; and the subgenital plate bears short styli with a narrow interspace between styli unlike that in I. caligula ; the new species is distinctly smaller in size than I. caligula . Colouration. The overall colour is brownish green when alive; head brownish, including the fastigium, frons, clypeus, gena and scapus. Pronotum anterior margin brownish in dorsal view with posterior margin greenish; antennae pale brown, annulated with black rings at base; the segments black at apices. Tegmen appears green, but is hyaline with veins and veinlets green; hind wings hyaline, with veins and veinlets green; exposed apex similar to tegmen, appears more green. Stridulatory vein brown in the middle with the file border brown to black. Abdominal tergite brown, dorso-medially reddish. Apex of spines on legs black. Anterior legs generally green, but the specimen at hand is discolored brown. Anterior tibia tympanum yellowish to brown, hind leg apical spurs with black tips.