Bioacoustics of Orphnus (Phornus) giganteus

Description Male ( Fig. 1A ) Body length 10.0– 14.5 mm . Colour uniformly brown to black. Anterior margin of frontoclypeus slightly convex in middle, serrate and setose, without distinct border ( Fig. 1C ). Frontoclypeus with process near anterior margin, varying for conical tubercle to small horn ( Fig. 1D ). Eye tubercles more or less developed. Frontoclypeus rugose anteriorly up to eye tubercles, including base of frontoclypeal process, convex and finely but densely punctate behind eyes. Eyes small: width about 1/15 distance between eyes in dorsal view. Antennae 10-segmented, with malformed segments. In the majority of specimens antennomeres 5 and 6 partly fused ( Fig. 1G ). In one specimen the malformations are asymmetrical: the left antenna has antennomeres 5–7 partly fused ( Fig. 1E ) while the right has antennomeres 3–5 partly fused ( Fig. 1F ). Pronotum widely rounded laterally, as wide as elytra ( Fig 1M ). Anterior border wide, with somewhat undulate or serrate posterior margin. Basal border narrow, keel-shaped, separated from pronotal disc by deep groove with irregular punctation. Pronotal disc anteromedially flattened, with two distinct rounded tubercles in majority of specimens ( Fig. 1A ). Pronotum covered with dense rounded punctures. Scutellum subtriangular, rounded apically, about 1/12 length of elytra. Elytra 1.1 times longer than wide, with distinct humeral humps. Elytra widest in middle, lateral margins almost parallel in basal half. First seven striae feebly distinct as shallow grooves, somewhat shagreened in most specimens. Elytral intervals covered with relatively smaller punctures, much finer than those on pronotum. Macropterous. Stridulatory field: carinae separated by 1/39 length of field in central ¼ rd ( Fig. 1K ). Abdominal sternite 8 medially longer than sternites 6 and 7 combined; sternite 6 about as long as sternite 7. Pygidium almost invisible from above, with slightly truncate apex. Plectrum triangular with rounded apex, wider than long ( Fig. 1J ). Lateral plate of second abdominal sternite is less distinct than in other Phornus species, situated more laterally and appears as sharp lateral edge of sternite. Aedeagus with relatively long parameres (0.68 length of phallobase), somewhat angulate and rounded apically in dorsal and lateral view ( Fig. 1 H–I), with excavations on ventral side of parameres. Female ( Fig. 1B ) Female differs from the male in having a relatively smaller pronotum without tubercles, frontoclypeus uniformly densely punctured, without convexity and process, prothoracic spur, finer stridulatory area (carinae separated by 1/57 of field in central ¼ rd , Fig. 1L ), smaller plectrum, less distinct abdominal lateral plate, and pygidium with rounded apex. Body length of examined specimens varies from 11.0– 14.5 mm .