Segestes nostosalgos, Tan & Wahab, 2020

Tan, Ming Kai & Wahab, Rodzay Bin Haji Abdul, 2020, New taxa and notes on palm and false-leaf katydids (Orthoptera: Tettigoniidae: Mecopodinae, Sexavaini; Pseudophyllinae, Cymatomerini) from Brunei Darussalam, Zootaxa 4808 (2), pp. 301-316 : 303-306

Segestes nostosalgos sp. n.

( Figs. 1–3 )

Material examined. Holotype, 1 male (KB.19.14), Brunei Darussalam, Temburong District, Kuala Belalong Field Studies Centre, along Ashton Trail , N4.54563, E115.15696, 148.1± 6.6 m.a.s.l., 2031 hours, on foliage, 13 July 2019, coll. M. K. Tan & H. Yeo ( UBDM).

Genus status. Our specimen does not possess a small, posterior, dorso-apical spine on fore and middle tibiae, a character Willemse (1977) used to separate Segestes from other genera of the genus group Sexavae Karny, 1924. Cu1 of tegmen is running obliquely toward anal margin “hind margin” at a short distance from base of tegmen, distinguishing our specimen from Sexava Walker, 1870 .

Diagnosis. This species differs from all known congeners as well as species from Segestidea Bolívar, 1903 by smaller size and slender habitus; fastigium verticis with apex somewhat obtuse; knee-lobes with one spine; subgenital plate deeply and narrowly excised at apex and by the presence of very stout styli; tegmen very elongated and narrow; stridulatory file of left tegmen short and with few long teeth.

Comparison with congeners. This new species from Borneo appears more similar to species from the Philippines, Maluka/ Sulawesi and Java than those from Papua New Guinea and Bismarck Archipelago. It differs from S. beieri Kästner, 1934 from Philippines by the mirror on right tegmen more elongated, male subgenital plate with slightly deeper excision at apex and stouter styli; from S. celebensis Karny, 1931 from Sulawesi, it differs by the presence of a spine on outer knee lobe of hind femur and posterior margin of subgenital plate narrowly and deeply excised instead of triangularly excised; from S. frater Hebard, 1922 from Maluka, it differs by the more slender tegmen and appearing more rugose rather than smooth and shiny and Rs producing nearer to the apex, inner basal area of hind femur with a black stripe in the dorsal half and brownish ventral of this stripe instead of being pale, abdominal sternites whitish instead of red brown; from the female of S. fuscus Redtenbacher, 1892 from Philippines, it differs by the hind femur being distinctly paler coloured with dark brown stripes and patterns, but not unicolourous brown; from S. vittaticeps Stål, 1877 from Philippines, it differs by smaller habitus (PL = 4.6 vs. 5.5 mm) but with longer tegmen extending well beyond apex of subgenital plate (TL = 40.7 vs. 39 mm), the brown rather than green colouration, longer fastigium, and by the excision at the apex of the subgenital plate being narrow instead of broad triangular.

We could not compare our specimen with S. punctipes Redtenbacher, 1892 from the Philippines, which is only known from a female.

The new species differs from all New Guinean and Bismarck Archipelago species (i.e., S. brevipennis Willemse, 1977 , S. cornelii Willemse, 1977 , S. decoratus Redtenbacher, 1892 and S. stibicki Willemse, 1977 ) by the combination of these characters: fastigium verticis at apex somewhat obtuse, with excision in the middle (similar to S. decoratus ), but not spine-like as in S. brevipennis and S. stibicki ; apex of tegmen rounded instead of narrow or truncated; knee-lobes with one spine; smaller in size. It also differs distinctly from S. unicolor Redtenbacher, 1892 from Caroline Islands by brown colouration and more slender habitus.

Distribution. Currently known only from Brunei Darussalam. This is the first record of the tribe Sexavaini from Borneo. Sexavaini are previously known from the Philippines, Sulawesi, Maluka, Java, Papua New Guinea and Bismarck Archipelago, parts of Australia and Pacific oceanic islands.

Description. Habitus typical for genus, shown in Fig. 1 . Fastigium of vertex elongated, surpassing antennal scapus; tapering into subacute apex, minutely excised at apex; with longitudinal groove ( Fig. 2A ). Frons oblique, smooth; without lateral carinae ( Figs. 2B, 2C ). Maxillary palps elongated and slender; apical segment about as long as third segment, longer than subapical segment; apical segment slightly curved, with apex slightly more bulbous. Eyes very weakly protruding, oblong in dorsal view ( Figs. 2A, 2B ); median ocellus reduced, indicated only by lighter spot ( Fig. 2C ); lateral ocelli absent.

Pronotum rugose, 0.76 times as long as head; disc 1.04 times as wide as long, broadly rounded into paranota, apical area not raised and faintly shouldered ( Fig. 2A ); anterior margin slightly angularly convex in middle; posterior margin angularly convex ( Fig. 2A ). Lateral lobe about 1.59 times as long as high; lower margin angular; marginal fold of pronotum very narrow, smooth ( Fig. 2B ). Thoracic auditory spiracle slender-elongated, higher than long, not covered by paranota ( Fig. 2B ). Prosternum with two large acute spines diverging from one another ventrad. Mesosternal and metasternal lobes blunt ( Fig. 2D ).

Anterior coxa with a long spine pointing externally, apex acute ( Fig. 2D ). Anterior tibia with inner tympanum open and oval-shaped, outer tympanum conchate, with slit fairly wide and conchate cover slightly swollen. Femora with following number of robust spines on ventral margins: anterior femur 1 to 3 inners near knees, 0 outer; middle femur without spines; posterior femur with 8 outer and 8 to 11 inner spines. Knee lobes of anterior and middle femora with one short spine externally and internally; of posterior femur with 2 inner spines and 1 outer spine. Tibiae with following number of spines: anterior tibia 6 to 7 subapical ventral spines, 2 apical smaller ventral ones; middle tibia 6 ventral spines and on outer margin with 5 dorsal spines; posterior tibia with row of dorsal and ventral spines on both inner and external margins, ventral spines more numerous on outer than inner margins, dorsal spines regular.

Male. Macropterous, tegmen well surpassing abdominal apex and hind femur, apex rounded ( Fig. 1 ). Stridulatory file on CuPb on underside of left tegmen straight; 2.33 mm long; with teeth evenly distributed; with circa 50 well developed teeth, teeth length becomes increasingly larger from anal to basal end, then becomes distinctly smaller at basal end ( Fig. 2E ). Mirror on left tegmen underdeveloped, with veins net-like ( Fig. 2F ). Mirror on right tegmen fully developed, rectangular, 1.29 times longer than wide, anterior margin rounded, slightly narrower than posterior margin ( Fig. 2A ). R and Sc diverge apically, Rs produced near the apex, R 1 produced just before apex. Hind wings completely concealed under tegmina.

Tergites with median carina, posterior margin produced into stout median lobe with rounded apex ( Fig. 3B ). Tenth abdominal tergite simple, with posterior end broadly and faintly excised in middle ( Fig. 3B ). Epiproct tongueshaped with apex excised in middle ( Fig. 3B ). Cercus typical of genus, elongated, slender, very faintly curved internally (more obvious apically), apex produced into a small acute sclerotized tooth ( Fig. 3C ). Subgenital plate elongated, shaft-like, posterior margin narrowly excised in middle, lateral lobes gently tapering to truncated apex; styli short, stout and conical, apex obtuse ( Fig. 3D ).

Female. Unknown.

Colouration. Dorsal half pale brown, ventral half whitish; with numerous dark brown stripes and patterns when alive; generally brown when dry-pinned ( Fig. 1 ). Face white, with dark curved stripe beneath scapus ( Fig. 2C ); gena also white, faintly pale brown behind eye, with longitudinal horizontal band extending from posterior margin of eye (just ventral of the middle) to posterior end of head; with thinner brown band extending from behind eye to posterior end of head above the thick band; with a thin dark stripe extending from ventral margin of eye and then posteriorly; with another thicker irregular horizontal dark band above base of mandible ( Fig. 2B ). Mouthparts white; maxillary palps whitish, with apices of segments very pale brown. Fastigium verticis with darkened at apex ( Figs. 2A, 2B ). Scapus dorsally brown, ventrally pale brown; antennae yellow brown. Dorsum of head pale brown, in midline dark- ened (including vertex), with narrow dark stripes extending from behind antennal scapus and eyes to posterior end of head ( Fig. 2A ). Pronotum with dorsal disc pale brown, along midline darkened especially in pronzona around median carina and extending laterally, longitudinal carina pale, metazona with a darkened lateral strip near shoulder ( Fig. 2A ). Lateral lobe of pronotum in dorsal half pale yellow with fissures dark, ventral half brown; margins pale yellow ( Fig. 2B ). Tegmen generally with cells infumated, some black; veins yellow or faintly coloured. Coxae white to very pale yellow. Femora generally whitish, dorsally very pale brown; outer surface with dark brown longitudinal stripe and spots; knee pale brown with dark marmoration, usually dark along ventral margin of genicular lobe, spine with apex darkened. Posterior femur pale brown with numerous small black spots especially on dorsal surface; inner basal area of hind femur with a black stripe in dorsal half and brownish ventral of this stripe. Spines on legs generally black at base and apex, red brown in middle (sometimes very dark red). Thoracic and abdominal tergites pale brown, with faint black patterns; thoracic and abdominal sternites generally white.

Measurements (in mm). BL = 30.5, PL = 4.6, PW = 4.8, TL = 40.7, HFL = 29.9, HTL = 29.0.

Natural history. Although species of the tribe Sexavaini are known as palm katydids because of the tendency to be found on palm leaves, the specimen collected from Kuala Belalong was found on the foliage of a tree in the understory.

Etymology. The species name refers to homecoming (nostos = homecoming in Greek) and pain (algos = pain, grief or distress in Greek). This species is dedicated to those who are far away from home during the Covid-19 pandemic and any difficult times.

Figures

FIGURE 1. Segestes nostosalgos sp. n. male holotype in its natural environment.

FIGURE 2. Segestes nostosalgos sp. n. male holotype: anterior half of body in dorsal (A) and lateral (B) views; face in anterior view (C); thoracic segments in ventral view (D); stridulatory file on the left tegmen in ventral view (E); basal part of left tegmen in dorsal view (F). Scale bars: 5 mm (A, B); 2 mm (C, D, F); 1 mm (E).

FIGURE 3. Segestes nostosalgos sp. n. male holotype: abdominal apex in lateral view (A), apical tergites in dorsal view (B); cercus in dorsal view (C); subgenital plate in ventral view (D). Scale bars: 2 mm (A, D); 1 mm (B, C).