Melaneremus, Karny, 1937

Tan, Ming Kai & Wahab, Rodzay Bin Haji Abdul, 2018, Notes on the taxonomy of poorly known Gryllacrididae (Stenopelmatoidea) from Brunei Darussalam, Borneo, Zootaxa 4462 (4), pp. 579-591 : 584-587

Melaneremus ? bellus, new species

( Figs. 3 , 4 )

Material examined. Holotype (female, KB.17.76), Brunei Darussalam, Ulu Temburong National Park, Kuala Belalong Field Studies Centre, primary ridge dipterocarp forest, N4.54731, E115.15697, 103.9± 8.7 m.a.s.l., on foliage of tree, 26 July 2017, 2031 hours, coll. M. K. Tan (dried pinned, ZRC).

Paratypes: 3 males, 2 females, same locality as holotype, coll. M. K. Tan (dried pinned, ZRC). female, KB.16.20, N4.54629, E115.15680, 133.9±9.0 m.a.s.l., on rattan leaf, 23 September 2016, 2149 hours; male, KB.16.22, N4.54706, E115.15720, 112.1±16.0 m.a.s.l., on foliage of tree, 23 September 2016, 2214 hours; male, KB.17.63, N4.54584, E115.15685, 103.3± 6.8 m.a .s.l., on foliage near ground, 25 July 2017, 2130 hours; female, KB.17.77, N4.54730, E115.15703, 99.8±6.0 m.a.s.l., on rattan leaf, 26 July 2017, 2041 hours; male, KB.17.90, N4.54655, E115.15688, 101.9± 7.5 m.a.s.l., on rattan leaf, 27 July 2017, 2038 hours.

Diagnosis. This apterous new species has female subgenital plate transverse and forming two parts: a small anterior lobe and a large posterior plate; anterior part forming a lobe, wider than long, broadly, deeply, and roundly emarginated with two lateral lobules; lobule with rounded apex; posterior part broadly triangular, with apex subacute. Male subgenital plate with posterior margin broadly emarginate, laterally forming a lobe where stylus is inserted. In both males and females, the new species has four stridulatory files on first and second tergites, with circa 5 (most anterior), 14, 15, and 18 (most posterior) teeth respectively.

Comparison. The new species differs from M. borneensis by shape of female subgenital plate; shorter ovipositor (15.8 vs. 19.2 mm), barely longer than posterior femur; male ninth abdominal tergite with distal part without median vertical furrow. It also differs from other Southeast Asian species: subapterous M. javanicus (Karny, 1924) (not trapezoidal with posterior margin emarginated) and M. larnacoides Karny, 1937 (not truncated). Male tenth abdominal tergite also differs from M. jacobsoni (Griffini, 1913) .

Description. Female holotype. Habitus as shown in Fig. 3 . Head not enlarged, barely wider than the pronotum width ( Fig. 4A ), with length circa 0.3 times of pronotum length. Vertex of fastigium slightly raised with apex truncated, circa twice the width of antennal scapus ( Figs. 4A, 4B ). Eye black, oval and prominent, with length in anterior view slightly longer than (1.2 times) length of scapus, and width in anterior view slightly shorter than (0.8 times) length of scapus; median ocellus very small, same height as the lower margin of antennal groove Fig. 4B ). Frons smooth ( Fig. 4B ); labrum ovoid, longer than wide, ventral margin slightly emarginated. Maxillary palps long and slender, apical segment longer than subapical segment and third apical segment. Pronotum smooth, circa 1.2 times wider than long; disk with anterior margin feebly convex in the middle, with two very shallow oval depressions on each side of a faint longitudinal sulcus, smaller one on the anterior half, the other near posterior margin; posterior margin broadly emarginated ( Fig. 4A ); dorsal lobe rounded into lateral lobe, surface smooth with sulcus barely visible, circa twice longer than deep, ventro-anterior angle broadly rounded, ventral margin almost straight, ventral angle truncated, broadly angular to posterior and ventral margins, and posterior margin nearly straight ( Fig. 4C ). Mesonotum and metanotum transverse, posterior margin straight, with similar circular depression as pronotum ( Fig. 4A ). Prosternum unarmed, but with two gently raised lobes, bearing a few setae. Mesosternal and metasternal lobes barely raised, but with a few long setae along margins. Apterous. Legs generally long and slender, with setae sparsely distributed. Anterior coxa with distinct but relatively stout and short spine. Anterior femur without spine, anterior tibia with 4–5 subapical ventral spurs on each margin; spurs with increasing size basally ( Fig. 4C ). Middle femur also without spines, middle tibia with 4–5 subapical ventral spurs on each margin, the spurs with increasing size basally. Posterior femur with 7 stout subapical spines on outer margin, 10 on inner margin.

Female. Four stridulatory files on first and second abdominal tergites, two on each tergite ( Fig. 4D ). Anterior row on first tergite short with 5 peg-like teeth. Second file, also on first tergite, longer, more than twice the length of anterior file, slightly curved, with 14 peg-like teeth. Third file on second tergite curved, with 15 peg-like teeth; teeth more densely packed than second file; posterior file on second tergite nearly straight, with 18 peg-like teeth; teeth more densely packed than third file. Second to posterior files of subequal length. Eighth abdominal tergite reduced, shorter than anterior abdominal tergite; ninth abdominal tergite also reduced, but slightly longer than eighth abdominal tergite, tenth abdominal tergite reduced, deeply emarginated in the middle, forming lateral lobe ( Fig. 4E ). Epiproct small and tongue-shaped, depressed in the middle ( Fig. 4E ). Cerci slender and short, tapering to an acute apex ( Fig. 4E ). Subgenital plate transverse, much wider than long, forming two parts, a small anterior lobe and a large posterior plate ( Fig. 4G ). Anterior part of subgenital plate forming a lobe, 0.6 times as wide as posterior part; lobe circa 2.4 times wider than long; broadly, deeply, and roundly emarginated, with two lateral lobules; each lobule with rounded apex ( Fig. 4G ). Posterior part of subgenital plate circa 2.3 times wider than long, broadly triangular, with apex subacute ( Fig. 4G ). Ovipositor long and feebly curved; margins smooth, with subobtuse apex ( Fig. 4F ).

Male. Four stridulatory files on first and second abdominal tergites, two on each tergite. Anterior file on first tergite short with 5 peg-like teeth. Second file, also on first tergite longer, more than twice the length of anterior file, slightly curved, with 13 peg-like teeth. Third file on second tergite curved, with 15 peg-like teeth; teeth more densely packed than second file; posterior file on second tergite nearly straight, with 19 peg-like teeth; teeth more densely packed than third file. Second to posterior files of subequal length.

Eighth abdominal tergite enlarged, longer than other tergites ( Fig. 4H ). Ninth abdominal tergite forming a hood ( Fig. 4H ). Tenth abdominal tergite with two processes in the middle; each process broadest at the base, internal margin straight while external margin converges, pointing ventrally and produce into a sclerotized and obtuse apex; with setae ( Fig. 4I ). Epiproct concealed beneath tenth abdominal tergite ( Fig. 4I ). Cercus long and slender, cylindrical and setose, curved internally at the posterior end, with acute apex ( Fig. 4I ). Subgenital plate circa 2.5 times wider than long; anterior margin broadly concave; lateral margin slightly converging posteriorly, with some setae; posterior margin broadly emarginated, laterally forming a lobe where stylus is inserted ( Fig. 4I ). Stylus short and stout, setose, with obtuse apex ( Fig. 4I ).

Colouration. Generally brown to orange brown. Head, including frontal rostrum and frons, generally brown; dorsum darker than genae and frons; maxillary palps and labrum pale brown; mandibles darker brown. Pronotum brown, with margins and sulci darker. Anterior and middle legs generally pale brown, including spurs; tibial spurs with white tips. Posterior legs also pale brown; spines on femur and tibia with black tips; tarsi pale. Thoracic segments pale brown; abdominal tergites brown, sternites pale brown in the middle and very pale at the sides.

Variation. In addition to variations in the measurements and number of spines and spurs on legs, the numbers of teeth on each stridulatory file can also vary between individuals, sex, and between the left and right side of each individual. It will be of interest to investigate how variable the stridulatory files are within conspecifics as well as congeners, and to assess if characters of the stridulatory files can be useful for assessing species boundaries.

Measurements. Table 1.

Etymology. The species name refers to the appearance of the gryllacridid and the female subgenital plate. From Latin, bellus = cute.

Figures

FIGURE 3. Melaneremus? bellus sp. nov.: a female with nuptial gift (A), males (B, C), and a mating pair (D).

FIGURE 4. Melaneremus? bellus sp. nov.: head and pronotum in dorsal view (A); face in anterior view (B); anterior half of body in lateral view (C); stridulatory files on abdominal tergite (D); female abdominal apex in posterior view (E); ovipositor in lateral view (F); female subgenital plate in ventral view (G); male abdominal apex in dorsal view (H); and male abdominal apex in ventral view (I). Scale bars: 5 mm (C, F); 2 mm (A, B, H); 1 mm (D, E, G, I).