Bioacoustics of Hygronemobius dialeucus

Comments. Hygronemobius dialeucus sp. nov. belongs to the amoenus group proposed by Desutter- Grandcolas (1993) . The male genitalia of Hygronemobius dialeucus sp. nov. is more similar to that of H. amoenus differing by: pseudepiphallic apical lobes apex longer and thinner ( Fig. 3 D–E); infero-posterior angle of pseudepiphallic sclerite rounded ( Fig. 3 F). Among species of amoenus group, position and shape of white spots are very important to determining the species, wherefore H. torquatus differs from H. dialeucus sp. nov. by having: dorsal disc of pronotum with a large transversal white stripe near its anterior margin and posterior margin without white markings; only a white dot on femur III; in females, tergites II–III with two pairs of lateral white dots and tergite IV black; H. albolineatus differs from H. dialeucus sp. nov. by having: two longitudinal white stripes running dorsally from fastigium to the posterior margin of pronotum, and in females reaching the tergite IX; a whitish dot behind the eyes; palpi without white markings; tibiae and tarsi without white dots; central portion of posterior margin of pronotum black; tegmina apex whitish. H. boreus differs from H. dialeucus sp. nov. by having: two longitudinal white stripes running dorsally from fastigium to the posterior margin of pronotum; central portion of posterior margin of pronotum black; in females, tergite II with a transversal white stripe, tergite III with white spots on lateral margins and tergite IV with central portion black; tibiae and tarsi without white dots. H. amoenus differs from H. dialeucus sp. nov. by having: head with two longitudinal thin white stripes, from fastigium to occiput; and two longitudinal white stripes along lateral margins of dorsal disc of pronotum. Calling song of H. amoenus , H. albolineatus and H. dialeucus sp. nov. are characterized by brief chirps with 3 pulses in H. amoenus , usually 4 pulses in H. albolineatus ( Desutter-Grandcolas 1993 ) and usually 5 pulses in H. dialeucus sp. nov. ( Fig. 4 B).

Description. Holotype , male, measurements (mm): body length, 6.0; pronotum length, 1.3; pronotum width, 2.0; head width, 2.0; length of femur III, 4.1; length of tibia III, 3.2; right tegmen length, 2.8; right tegmen width (dorsal field), 3.2. General color of the body black with some white markings. Head brown, except: vertex dark brown but the adjacent area to eyes light brown; occiput light brown; gena light brown; black eyes; scape e pedicel light brown; flagellum with the firsts antennomeres light brown becoming darker towards the apex; frons with an inverted dark brown T-shaped spot; clypeus, lateral portion of the postclypeus dark brown and center-basal portion of the anteclypeus whitish; labrum light brown, basal portion dark brown with a whitish stripe at the apex; Maxilla light brown, lacinia with whitish apex; maxillary palp: first two palpomere dark brown; third palpomere whitish with proximal portion dark brown; fourth palpomere whitish; fifth palpomere dark brown with whitish apex and third proximal portion light yellow; labial palp: first palpomere dark brown; second palpomere dark brown on proximal half and whitish on distal half; third palpomere from whitish to dark brown with apex whitish. Thorax , pronotum black with five white marks on the dorsal disc ( Fig. 5 A): anterior margin, a pair of dots; posterior margin, three dots, the lateral ones bigger; lateral lobe evenly black ( Fig. 5 C); pronotum with black fine pubescence and strong bristles covering all its extension. Dorsal field of right tegmen dark brown with light yellow spots ( Fig. 5 D) situated: 1) close to insertion of tegmen on metanotum; 2) on junction of anal veins; 3) distal portion of cordal area; 4) continuous band between Cu1 and M veins until external portion of apical area; 5) large spot between longitudinal vein in harp and Cu1. Lateral field of right tegmen with five veins; color pattern: a long dark yellow band between R vein and superior vein of lateral field; proximal and supero-distal portions dark brown, remaining areas lighter. Hindwings absent. Prosternum dark brown. Mesosternum dark brown with posterior third light brown. Metasternum dark brown. Legs I and II with similar pattern: coxae and trochanteres dark brown; femora dark brown to black with an elongated white dot on dorsal face ( Fig. 5 A); tibiae dark brown, tibia I with an oval tympanum on outer face; tarsi dark brown, first tarsomere with a dorsal elongated white spot. Leg III: coxa and trochanter dark brown; femur III black, knee and proximal area of lighter color, two white dots on the inner face, the distal bigger than the proximal ( Fig. 5 A); tibia III black with an elongated white spot close the last inner dorsal spur ( Fig. 5 A); tarsus III dark brown, first tarsomere with a dorsal elongated white spot. Abdomen, tergites black; a continuous band comprising latero-distal portion of tegite IX, proximal half of supranal plate and cerci adjacent area ( Fig. 5 A); supranal plate with apex rounded ( Fig. 5 E); sternites I–IV dark brown, sternites V–VII dark brown in central portion and black in laterals, sternite VIII evenly black ( Fig. 5 B); subgenital plate black with distal and lateral margins rounded; cerci light brown. Male genitalia ( Fig. 3 D–F): pseudepiphallic sclerite sub-trapezoidal, distal margin twice wider than the proximal margin; pseudepiphallic apical lobes well developed, longer than half length of pseudepiphallic sclerite; numerous smalls setae presents only on pseudepiphallic apical lobes; pseudepiphallic median lobes with distal margin rounded, visible in lateral view; ectophallic fold large, as long as pseudepiphallic sclerite, and as high as pseudepiphallic median lobes (in lateral view, Fig. 3 F); ectophallic apodeme crossing and surpassing rami ( Fig. 3 E); endophallus divided in three sclerites, the lateral sclerites triangular and larger than the central one ( Fig. 3 D–E). Observations in paratypes . Stridulatory file of right tegmen with 80–95 teeth (n=5). White band on terminal tergites not continuous forming two spots separated by a narrow black stripe ( Fig. 1 C). Female, body shape and color pattern similar to Holotype , except: tegmina reduced to black lateral scales ( Fig. 1 D); posterior margin of pronotum with a wide white stripe slightly incurved on lateral lobes ( Fig. 1 D); tergite IV with a wide transversal white band ( Fig. 1 D); supranal plate dark brown ( Fig. 5 G); subgenital plate from dark to light brown, sub-rounded with a central invagination on apex ( Fig. 5 H); all sternites dark brown; prosternum dark brown; mesosternum dark brown with posterior half light brown; metasternum dark brown; ovipositor, valves dark brown, proximal two-thirds of ventral valves light brown ( Fig. 5 I); apex of the dorsal valves slightly denticulate on their margins ( Fig. 5 I). Calling song (25.5–28°C, Tab. 0 1, Fig. 4 B): 5 pulses per chirp, rarely chirps with 4 pulses; chirp duration with 5 pulses of 91 ± 7 ms (83–99, n=40); inter-chirp interval of 272 ± 29 ms (220–330, n=40); chirp rate of 160 ± 15,67 chirps/min (140–176, n=4); pulse duration of 8.13 ± 0.43 ms (7–9, n=30); dominant frequency of 7.3 ± 0.39 kHz (6.8–7.7, n=4). Habitat and male calling site. Males and females live in litter and were collected only inside the forest. Males were seen stridulating on soil under dry leaves during daytime.