Bioacoustics of Siamgryllacris

Description. Medium sized species; some individuals smaller. Head: Face ovoid; forehead nearly smooth with some very fine riffles or impressed dots; fastigium verticis little wider than scapus, separated by a transverse suture from fastigium frontis; ocelli distinct, yellow; subocular furrow indistinct, shallow ( Fig. 85H . Abdominal tergites two and three without stridulatory pegs. Wings surpassing hind knees ( Figs. 85 A–E). Tegmen: Radius with two branches, both forked near tip; media anterior free from base but in basal area closely approached to radius; cubitus anterior with a single branch at base that divides near end of basal quarter into CuA1 and CuA2; the anterior branch (CuA1) closely approaches MA in a curvature and is connected by a strong cross-vein at the point of closest approach, when it deviates again it divides into MP and CuA1. Variation: in two specimens MP fuses for a short distance, about one cell length, with MA; in one female only on left tegmen MP arises from MA while CuA remains undivided, single branched to tip. Cubitus posterior undivided, free throughout; with 4 anal veins the last two with a common stem. Legs: Fore coxa with a spine at fore margin; fore and mid femora unarmed; fore and mid tibiae with four pairs of large ventral spines and one pair of smaller ventral spurs; hind femur with 3–11 external and 6–16 internal spines on ventral margins; hind tibia with spaced spines on both dorsal margins, ventral margins with one pre-apical spine; with 3 apical spurs on both sides. Coloration. General color uniformly brown; vertex, pronotum, tip of abdomen, genicular area of hind femur legs and all tibiae dark purplish red; most spines on femora and tibiae black, the moveable spines on fore and mid tibiae black with white tip. Face yellowish brown with indistinct marbleization; vertex dark brown; compound eyes dark brown. Tegmen semi-transparent yellow, veins little darker; hind wing semi-transparent white; veins and veinlets pale yellow to brown ( Figs. 100 F–G). Male. Eighth abdominal tergite prolonged. Ninth abdominal tergite globular, down-curved posterior surface with a shallowly depressed groove with a furrow in middle; on top of groove with a small granular conical process over the upper end of the furrow. Tenth abdominal tergite band-shaped, in middle with a pair of posteriorly projecting processes with thickened globular swellings that carry along internal margins a rather wide, compressed, stiffened, black, vertical rim ( Figs. 86 A–E). Epiproct small, largely covered by paraproctes, latter forming large plates mediad of bases of cerci, little overlapping in middle. Subgenital plate little wider than long; lateral margins in roughly basal half with slightly diverging lateral margins, thereafter with converging lateral margins, apical margin substraight, faintly concave; the short (less than half the length of subgenital plate) and thin styli inserted behind the lateral angles ( Fig. 86F ). Phallus membranous. Female. Sixth abdominal sternite with a short conical projection overlapping base of seventh sternite. Seventh sternite with basal margin little excised in middle fitting the process of the sixth sternite, otherwise without striking modification, apex passes into a long membranous zone between seventh sternite and subgenital plate, sometimes building folds. Subgenital plate separated by a prolonged membranous zone from preceding sternite, sclerotised part regularly vaulted with little converging lateral margins; apical margin strongly concave ( Figs. 86 G–K). Base of ovipositor at very base of ventral valves with a small swelling. Ovipositor elongate, in subbasal area little upcurved, afterward straight or substraight, in about apical half with gradually approaching margins; before tip margins more strongly narrowed, tip subobtuse ( Fig. 85I ). Measurements ( 11 males , 6 females ).—body w/wings: male 26–34, female 27–28; body w/o wings: male 23.0–28.5, female 24–27; pronotum: male 3.5–5.2, female 4.5–5.5; tegmen: male 20.0–25.5, female 20–21; tegmen width: male 6.5–6.8, female 6.0–6.5; hind femur: male 11.5–15.5, female 12.5–13.0; antenna: male 90–110, female 90–110; ovipositor: female 16.5–18.0 mm.