﻿Three new species of the genus Biasticus Stål, 1867 (Insecta, Heteroptera, Reduviidae, Harpactorinae) from Central Highlands, Vietnam

﻿Abstract Three new assassin bug species of the genus Biasticus Stål, 1867 are recognized in Vietnam based on morphological examination, morphometric and molecular phylogenetic analyses, and described as Biasticustaynguyenensis Ha, Truong & Ishikawa, sp. nov., Biasticusgriseocapillus Ha, Truong & Ishikawa, sp. nov., and Biasticusluteicollis Ha, Truong & Ishikawa, sp. nov. The conspecific male and female associations of the new species were confirmed by phylogenetic analyses and DNA barcoding of the mitochondrial 16S rDNA and COI genes. All three new species are presently restricted to the Central Highlands, Vietnam (Kon Chu Rang NR, Gia Lai Province, and Chu Yang Sin NP, Dak Lak Province).

We discovered dozens of Biasticus specimens in Central Highlands, Vietnam, during recent field surveys and examinations of Reduviidae specimens owned by research organizations in Vietnam, Thailand, Laos, Taiwan, and Japan, but they were not identifiable as valid species of the genus. Therefore, this study aims to confirm the taxonomic status of those Biasticus specimens using an integrated approach that includes morphological examination, morphometric analyses, molecular phylogenetic analyses, and molecular-based species delimitation analyses, i.e., Assemble Species by Automatic Partitioning (ASAP) (Puillandre et al. 2021) and Bayesian implementation of the Poisson Tree Processes model (bPTP) ) for species delimitation, as well as the necessary taxonomic treatments.

Morphological examination and imaging
External structural characteristics were observed for dry-mounted and ethanol-preserved specimens using a Nikon SMZ1270 stereomicroscope. The genitalia were prepared for examination as described below. Firstly, each male specimen was relaxed by soaking for 3 days in 70% ethanol. After that, the male genitalia was detached from the body and then soaked in hot 10% KOH for five minutes until body fat and muscle was released. The endosoma was pulled out of the phallosoma by fine tweezers after removing the phallus from the pygophore. All parts of male genitalia were preserved in a genitalia vial filled with propylene glycol and subsequently associated with the pinned specimens. Next, the female genitalia were inspected without being detached from the body. A Nikon SMZ1270 stereomicroscope was used to examine the male and female genital morphology. Focus stacking was executed using Helicon Focus Pro 7.5.3 software (Helicon Soft Ltd., Ukraine) based on a sequence of the source pictures photographed by a Canon EOS Kiss X9 digital camera connected to a Nikon AZ100 stereomicroscope, and artifacts were removed using the retouch function of the software. After that, the contrast, brightness, color balance, and intensity were adjusted using Adobe Photoshop Elements 10.0 software (Adobe Systems Incorporated, San Jose, CA, USA) using a color corresponding sticker (CASMATCH, Bear Medic Corporation, Japan).

Morphometric analyses
Considering the weak to moderate sexual dimorphism of external morphology, the Principal Component Analyses (PCA) were performed separately for the female adult and male adult datasets using R software 4.1.2 (R core team 2021). The morphometric , and length of left hind tibia (PTL)), and proportion of mean values of three color indices (mR, mG, and mB) of the central region of posterior pronotal lobe to sum of mR, mG, and mB (mRr = mR/ (mR + mG + mB), mGr = mG/(mR + mG + mB), and mBr = mB/(mR + mG + mB)). The function "fviz_pca_ind" (factoextra package) (Kassambara and Mundt 2020) was used to graph the 2D plot of PCA. To determine the most prominent contributing morphometric characters in each male and female dataset, we used the "get_pca_var" (factoextra package) function to test the contribution of variables to the dimensions of PCA (Kassambara and Mundt 2020).
Raw morphometric datasets and the R-scripts used for the data design and analyses are presented in additional files (Suppl. materials 1-3).

Molecular data preparation
DNA was isolated from the right or left hind tibia of each specimen by the Chelex-TE-ProK protocol (Satria et al. 2015). The mitochondrial 16S and COI gene fragments were examined using the primers presented in Table 2. Polymerase chain reaction (PCR) amplification, cycle sequencing reaction, sequencing using ABI PRISM 3130xl (Applied Biosystems), and sequence assembly using ChromasPro 1.7.6 (Technelysium Pty Ltd., Australia) were executed using the methods of Satria et al. (2015), Simon et al. (1994), Cognato and Vogler (2001), Meusnier et al. (2008), Shekhovtsov et al. (2013), Bely and Wray (2004), and Zhang and Weirauch (2013). The PCR thermal situation for the two gene fragments, 16S and COI, comprised of initial denaturation 94 °C (2 min), denaturation 94 °C (30 s), annealing at appropriate annealing temperature (30 s) ( Table 2) (OG+) and Uni-Minibar (OG+) datasets were aggregated to produce a concatenated 16S + Uni dataset (661 bp). The FASTA-configured files derived from MEGA X were then converted to NEXUS layout or PHYLIP design, which were suitable input layouts for molecular phylogenetic examination and estimation of genetic distances and species delimitation analysis by ClustalX 2.0.11 (Larkin et al. 2007).

Molecular phylogenetic analyses
Molecular phylogenetic analyses were done based on the concatenated 16S + Uni dataset since the number of specimens that were successfully obtained 16S gene fragment and Uni-Minibar gene fragment were the highest. The substitution models, K3Pu + F + I + G4, TIM2e + G4, and (K3Pu + F + I + G4, TIM2e + G4), were selected respectively for the 16S (OG+) , Uni-Minibar (OG+) , and the concatenated 16S + Uni datasets by Model Finder (Kalyaanamoorthy et al. 2017) executed in IQ-TREE 2.1.2 (Minh et al. 2020). Maximum likelihood (ML) examinations were then carried out using IQ-TREE 2.1.2 (Chernomor et al. 2016;Minh et al. 2020); bootstrap values (BP) were estimated from 1,000 replications. The generalized time-reversible (GTR) + Gamma model was chosen for the 16S + Uni dataset using Model Finder (Kalyaanamoorthy et al. 2017) under the Bayesian information criterion. The Bayesian inference (BI) evaluations were then executed for the data using MrBayes v. 3.2.6 (Ronquist and Huelsenbeck 2003) with 20,000,000 production and statutory parameter configuration (examining every 500 generations and tuning constraints every 100 generations,  with a burn-in of 25%). The effective sampling size (ESS) of each constraint was verified to be > 200 using Tracer 1.7.1 (Rambaut et al. 2018). The nodes were designated as "well supported" when posterior probability (PP) ≥ 0.95 and BP ≥ 80.

Species delimitation analyses
To create species partitions, two different protocols, i.e., Assemble Species by Automatic Partitioning (ASAP) (Puillandre et al. 2021) and

Examination of genital morphology in the female and male
Thirty-five female specimens were grouped into six female-based morphospecies (fA-fF) based on the characteristics observed in the externally visible part of genitalia. The type fA (= Biasticus taynguyenensis sp. nov.) (6 specimens) was characterized by the following features: abdominal sternite VII (AS7) forming a semicircular or broad subpentagonal median concavity, with inner posterolateral margin very weakly sinuate; gonocoxa VIII (Gc8) with posterior margin gently slanting anteromesad, with apical inner corner weakly produced mesad and forming an acute apex, with inner margin weakly incurved in rear 2/3; abdominal laterotergite VIII (AL8) visible as a thin bridge above the posteromedian part of abdominal tergite IX (AT9) (Figs 5A, 15A). The type fB (= B. griseocapillus sp. nov.) (3 specimens) was characterized by the following features: AS7 forming a broad subpentagonal posteromedian concavity, with inner posterolateral margin almost straight; Gc8 with posterior margin gently slanting anteromesad, with an apical inner corner but not formed, with inner margin strongly slanting anteromesad and slightly incurved; AL8 visible as a thin bridge above the posteromedian part of AT9 (Figs 5B, 18A). The type fC (= B. luteicollis sp. nov.) (12 specimens) was characterized by the following features: AS7 producing a wide subrectangular concavity, with posteromedian margin almost straight, with inner posterolateral margin poorly sinuous; Gc8 with almost horizontal and poorly sinuous posterior margin, with apical inner corner weakly and formed posteromesad and forming a blunt apex, with inner margin strongly incurved in its posterior 2/3; AL8 visible as a relatively thick bridge above the posteromedian part of AT9 (Figs 5C, 21A). The type fD (= B. flavinotus) (7 specimens, including lectotype) was characterized by the following features: AS7 forming a wide subrectangular concavity, with posteromedian margin poorly incurved, with inner posterolateral margin poorly sinuous; Gc8 with almost horizontal and poorly sinuous rear margin, with rounded apical inner corners, with inner margin considerably slanting anteromesad in rear 2/3; AL8 visible as a thin bridge above the posteromedian part of AT9 (Figs 5D, 7F). The type fE (= B. confusus) (3 specimens) was characterized by the following features: AS7 forming a wide subpentagonal concavity, with inner posterolateral margin almost straight; Gc8 with rear margin slightly slanting anteromesad and almost incurved, with apical inner corner poorly formed posteromesad and producing a blunt apex, with inner margin considerably incurved in its rear 2/3; AL8 apparent as a thin linkage above the posteromedian part of AT9 (Figs 5E, 8F). The type fF (= B. flavus) (5 specimens) was characterized by the following features: AS7 forming a wide subrectangular concavity, with posteromedian margin nearly straight, with inner posterolateral margin almost straight; Gc8 with posterior margin slightly slanting posteromesad and slightly incurved, with apical inner corner poorly developed posteromesad and producing an acute apex, with inner margin weakly sinuous; AL8 visible as a thin bridge above the posteromedian part of AT9 (Figs 5F, 10A). In contrast, based on characteristics present in male genitalia (pygophore and aedeagus), 17 adult male specimens were divided into four male-based morphospecies (mA-mC, mF). The type mA (= B. taynguyenensis sp. nov.) (1 specimen) was characterized by the following features: the median process of pygophore (mpp) broad and low, with apical margin weakly and progressively concave, with apicolateral corner specifically formed posterolaterad and emarginated (Figs 6A, 15B-E); endosoma with spoon-like sclerites (sps) hyaline and glabrous (Figs 6B, 15I); distal dorsal lobe of  (Matsumura, 1913), ♀, HNL2018-117 E type fE, B. confusus Hsiao et al., 1979, ♀, VN-Hem-1998-012 F type fF, B. flavus (Distant, 1903), ♀, LA-Redu-2004-006.

Examination of other morphological features in the female and the male
Fifty-six Biasticus specimens were sorted into six morphospecies (bA-bF) based on external body morphology. The type bA (= B. taynguyenensis sp. nov.) consisting of fA and mA was characterized by the following features: body shiny blackish brown (Fig. 13A); base of first visible labial segment yellowish brown, remaining of labium black, tips of first and second visible labial segments pale luteous (Fig. 13D); scape ~ 1.5 × as long as head, pedicel slightly longer than first flagellomere and ~ equal in length to second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 3.1:1.6:1.4:1.6; anterior pronotal lobe blackish brown or black with some rows of short bent cream-yellow setae (Fig. 14A, B); posterior pronotal lobe blackish brown or dark brown, densely covered with short bent cream-yellow setae, interspersed with long erect setae (Fig. 14A, C, D); scutellum wholly black or blackish brown (Fig. 14A); abdominal mediotergites I+II to IV and middle of mediotergite V blackish brown; posterior half of mediotergite V to apex of abdomen, and abdominal sternites sanguineous (Fig. 13A, B); laterotergites II-IV luteous, anterior half of laterotergite V suffused with brown, posterior half of laterotergite V to apex of abdomen sanguineous (Fig. 13B); femora and tibiae blackish brown (Fig. 13A, B). The type bB (= B. griseocapillus sp. nov.) consisting of fB and mB was characterized by the following features: body shiny blackish brown (Fig. 16A); first visible labial segment brown, second and third visible labial segments blackish brown, tips of first and second visible labial segments yellowish brown (Fig. 16D); scape ~ 1.5 × as long as head; pedicel slightly longer than first flagellomere and nearly equal in length to second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 3.0:1.6:1.4:1.6; anterior pronotal lobe black or blackish brown with some rows of long bent griseous setae (Fig. 17A, B); posterior pronotal lobe blackish brown or brown and densely covered with short bent griseous setae somewhat interspersed with long griseous setae (Fig. 17A, C, D); scutellum black in basal half and dark brown or brown in lateral margin and apical half (Fig. 17A); abdominal mediotergites I+II to V reddish brown or sanguineous, somewhat suffused with blackish brown, mediotergite VI suffused with reddish brown and irregularly suffused with sanguineous, mediotergite VII to posterior apex of abdomen sanguineous; abdominal sternites shiny sanguineous (Fig. 16B); laterotergites II-VI luteous, segmentally suffused with dark brown spots or blackish brown spots, laterotergite VII sanguineous (Fig. 16B); femora and tibiae blackish brown. The type bC (= B. luteicollis sp. nov.) consisting of fC and mC was characterized by the following characters: body shiny luteous (Fig. 19A); first visible labial segment and base of second visible labial segment luteous, apical 2/3 of second visible labial segment to third visible labial segment yellowish brown or brown (Fig. 19D); scape ~ 1.3 × as long as head; pedicel ~ as long as first flagellomere and ~ 0.7 × as long as second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 2.7:1.3:1.3:1.7; pronotum covered with long thick erect setae (Fig. 20A, C); anterior pronotal lobe, except lateral margin, shiny dark brown, sometimes with luteous suffusion centrally (Fig. 20B); posterior pronotal lobe luteous (Fig. 20A); scutellum dark brown in basal half and luteous in apical half, with median pale brownish luteous portion (Fig. 20A); abdominal mediotergites, except posterior half of mediotergite VII, dark brown and darker backward, posterior half of mediotergite VII luteous; abdominal sternites pale luteous (Fig. 19B); connexivum pale luteous, with segmentally dark brown suffusions (Fig. 19B); femora luteous with dark brown or yellowish brown suffusions at apex and sometimes at middle (Fig. 19A). The type bD consisting of fD only was characterized by the following features: body black (Fig. 7A); first and third visible labial segments and base of second visible labial segment black, remaining of second visible labial segment blackish brown (Fig. 7D); scape nearly 1.5 × as long as head; pedicel ~ 0.6 × as long as first flagellomere and ~ 0.4 × as long as second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 2.9:1.1:1.7:2.4; pronotum covered with short bent cream-yellow setae (Fig. 7E); anterior pronotal lobe black, posterior pronotal lobe luteous (Fig. 7E); scutellum wholly blackish brown to black (Fig. 7E); abdominal mediotergites, except lateral margins of mediotergite VII, blackish brown or dark reddish brown, lateral margins of mediotergite VII luteous; abdominal sternites luteous with some blackish brown or black segmental transverse stripes laterally (Fig. 7B); connexivum yellow to sanguineous (Fig. 7B); femora and tibiae black (Fig. 7A). This morphospecies corresponded to B. flavinotus. The type bE consisting of fE only was characterized by the following features: body shiny black (Fig. 8A); labium dark brown (Fig. 8D); scape ~ 1.7 × as long as head, pedicel approximately equal in length to first flagellomere and shorter than second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 3.5:1.6:1.6:2.1; pronotum dark brown to blackish brown (Fig. 8E); central disc of scutellum blackish brown, remaining of scutellum dark brown (Fig. 8E); abdominal mediotergites and sternites luteous to pale sanguineous (Fig. 8B); connexivum sanguineous (Fig. 8B); femora and tibiae dark brown to blackish brown (Fig. 8A). This morphospecies corresponded to B. confusus. The type bF consisting of fF and mF was characterized by the following features: body shiny black (Fig. 9A); labium blackish brown, paler apically (Fig. 9D); scape ~ 1.5 × as long as head, pedicel slightly longer than first flagellomere and subequal in length to second flagellomere; proportional average length of scape, pedicel, first and second flagellomeres 3.2:1.7:1.4:1.7; pronotum densely covered with long thick yellow erect setae (Fig. 9E); anterior pronotal lobe blackish brown to black with some rows of short yellow bent setae (Fig. 9E); posterior pronotal lobe luteous, somewhat anteriorly centrally suffused with blackish brown (Fig. 9E); scutellum blackish brown to black, except posterior halves of lateral margins and posterior apex luteous (Fig.  9E); abdominal mediotergites luteous with irregular brown suffusion, sometimes mediotergites wholly brown; abdominal sternites luteous with some blackish brown or black segmental transverse stripes laterally (Fig. 9B); connexivum pale luteous to luteous (Fig. 9B); femora and tibiae blackish brown to black (Fig. 9A). This morphospecies corresponded to B. flavus.

Morphometric analyses
The six female-based morphospecies (fA-fF) were discriminated from each other by PCA based on the morphometric dataset of female adults (Fig. 11A). Similarly, PCA based on the morphometric dataset of male adults, also revealed a significant separation of two groups, i.e., mC and B. flavus (mF) and three singletons, i.e., mA, mB, and B. confusus (mE) (Fig. 11B). For B. flavinotus, the mature male specimen was unavailable.

Phylogenetic analyses and DNA barcoding
Based on the concatenated 16S + Uni dataset (Fig. 12), each of the six morphospecies (bA-bF) was recovered as an independent clade with high supporting values (PP = 1; BP ≥ 93) and long basal branches in both BI and ML trees. The phylogenetic portioning was supported consistently by ASAP and bPTP based on the COI (OG−) , Uni-Minibar (OG−) , and 16S (OG−) datasets (Fig. 12). That is to say that the conspecific female and male association was presumed for the following cases: bA (fA = mA), bB (fB = mB), bC (fC = mC) and bF (fF = mF; B. flavus). The males of B. flavinotus and B. confusus have not yet been collected by us.

Species discrimination and identification
The bA, bB, and bC, of which each was confirmed to be an independent species, were distinguished also from 20 named congeners including the following three species already known from Vietnam, namely, B. confusus Hsiao et al., 1979 (= bE), B. flavinotus (Matsumura, 1913) (= bD), and B. flavus (Distant, 1903) (= bF), based on the features of external and genital morphology that have been used in diagnosing species of Biasticus and other related genera. The species bA, bB, and bC are therefore named and described as Biasticus taynguyenensis Ha, Truong & Ishikawa, sp. nov., B. griseocapillus Ha, Truong & Ishikawa, sp. nov., and B. luteicollis Ha, Truong & Ishikawa, sp. nov., respectively. The present study effectively identified a set of morphological features in female and male adults that can be used to classify aged specimens in existing collections that are not suitable for molecular phylogenetic analysis: the morphology of the posterior margin of AS7 and of the apical inner corner and the posterior and inner margins of Gc8 in the female genitalia; the morphology of mpp, sps, ddl, and dps and aa in the male genitalia; length of scape (A1L), length of pedicel (A2L), length of second flagellomere (A4L), length of right hemelytron (HeL), length of Sc in the right hemelytron (Sc), proportions of mean values of green and blue color indicators (mG and mB) of the central region of rear pronotal lobe to sum of mR, mG, and mB (mGr = mG/(mR + mG + mB), and mBr = mB/(mR + mG + mB)), head length (HL), and length of anteocular area of head (AoL) of the female adult (Table 3); length of left fore and hind tibiae (ATL, PTL), length of left femora (AFL, MFL, PFL), proportion of mean value of green color indicators (mG) of the central region of rear pronotal lobe to sum of mR, mG, and mB (mGr = mG/(mR + mG + mB)), length of scape (A1L), and maximum diameter of left ocellus (OD) of the male adult (Table 3).

Taxonomic account
Family Reduviidae Latreille, 1807 Subfamily Harpactorinae Amyot & Serville, 1843 Diagnosis. Body shiny blackish brown; anterior pronotal lobe blackish brown or black with some rows of short bent cream-yellow setae; posterior pronotal lobe blackish brown or dark brown, densely covered with short bent cream-yellow setae, interspersed with long erect setae; scutellum black or blackish brown; abdominal sternites sanguineous; laterotergites II-IV luteous; anterior half of laterotergite V suffused with brown; posterior half of laterotergite V to apex of abdomen sanguineous. This species is similar to B. confusus Hsiao et al., 1979 in general appearance, especially in body color, pronotum, and thoracic sterna. But the new species can be distinguished from B. confusus by a combination of the following characters: antennal pedicel longer than first flagellomere (in B. confusus pedicel as long as first flagellomere), second flagellomere as long as pedicel (in B. confusus second flagellomere longer than pedicel), proportional average length of first to third labial segments 1.1:1.4:0.3 (in B. confusus 0.9:1.2:0.3), anterior pronotal lobe with some rows of bent setae (in B. confusus without row of bent setae), posterior pronotal lobe ~ 2.3 × as long as anterior pronotal lobe (in B. confusus 2.0 ×), and apical margin of median process of pygophore weakly and continuously concave (in B. confusus weakly and continuously convex).
Furthermore, this species is somewhat similar to B. ventralis Hsiao et al., 1979 in general colors of body, pronotum, and sterna but the new species can be distinguished from B. ventralis by a combination of the following characters: antennal pedicel longer than first flagellomere (in B. ventralis pedicel ~ 1/2 as long as first flagellomere), second Description. Female description. Coloration. Body shiny blackish brown. Head dorsum shiny black or blackish brown; clypeus blackish brown; antenniferous tubercle, base of neck, maxillary plate, and base of first visible labial segment yellowish brown; central fascia to head venter, gena, tips of first and second visible labial segments pale luteous; labium, except base of first visible labial segment, black; a brown stripe present after postero-upper corner of compound eye; area around lateral ocellus with reddish brown suffusion; a longitudinally elongated yellowish brown spot present between lateral ocelli. Base of scape dark brown; remaining of scape brown; pedicel, first and second flagellomeres brown, darker toward tip. Collar, anterior pronotal lobe, thoracic sterna, and pleura blackish brown or black; posterior pronotal lobe blackish brown; scutellum black or blackish brown; stridulatory sulcus, intersecting area of coxa and trochanter yellowish brown; coxae, trochanters, femora, and tibiae blackish brown. Corium and clavus blackish brown, apically brownish yellow; membrane bronzy brown, semi-hyaline. Hind wings faintly semi-hyaline. Abdominal mediotergites I+II to IV and middle of mediotergite V blackish brown; posterior half of mediotergite V to apex of abdomen and abdominal sternites sanguineous; laterotergites II-IV luteous; anterior half of laterotergite V suffused with brown; posterior half of laterotergite V to apex of abdomen sanguineous. Female external genitalia sanguineous.
Vestiture. Body clothed with cream-yellow setation. Head, except interocular sulcus and area along anterior margin of compound eye, covered with short bent creamyellow pubescence, and sparsely with long erect setae; labium with a few bent setae; scape without setae and pubescence; pedicel, first and second flagellomeres with short vertical setae; neck glabrous. Collar, anterior margin, lateral area of anterior pronotal lobe, posterior pronotal lobe, scutellum, pleura, thoracic sterna, and coxae densely covered with short bent cream-yellow pubescence; posterior pronotal lobe, pleura, thoracic sterna, and coxae interspersed with long erect setae; scutellum with long bent slender setae, especially in lateral slopes and in posterior apex; trochanters, femora, and tibiae with short erect setae; corium with short bent setae. Abdomen (including connexivum), except segment VII, with short slender vertical setae; gonocoxa VIII (Gc8) with long slender bent setae.
Male description. General external morphology similar to that of the female. Coloration. Almost similar to female but slightly brighter than female. Clypeus dark brown; anteclypeus, base of first visible labial segment pale yellowish brown; first and third visible labial segments brown; second visible labial segment dark brown; area around ocellus with pale brown suffusion. Prosternum and propleuron blackish brown; posterior pronotal lobe dark brown; scutellum blackish brown; meso-and metapleura brown or yellowish brown; meso-and metasterna yellowish brown; fore coxa pale yellowish brown; coxae and trochanters of mid and hind legs yellowish brown; femora and tibiae dark brown or blackish brown. Pygophore ventrally orangish sanguineous; paramere semi-hyaline, pale orange.
Structure. Almost same as female except for the following characters. Scape 1.7 × as long as head; pedicel, first and second flagellomeres missing. Hemelytra surpassing apex of abdomen when fully closed, nearly 0.9 × as long as body length. Pygophore elliptic; median process of pygophore (mpp) broad and low, 0.3 × as long as wide, with apical margin weakly and continuously concave, with apicolateral corner distinctly produced posterolaterad and pointed; paramere long, slender, clavate, somewhat incurved in apical part, with round apex (Figs 6A, 15B-E). Aedeagus in dorsal view ovoid, dorsally sclerotized (Figs 6B, 15F, I) and in lateral view long and narrow (Figs 6C, 15G, K); articulatory apparatus (aa) in ventral view with basal plate arms relatively slender and jointly forming a U-shape, and in lateral view arched very strongly (Figs 6C, D, 15G, H); dorsal phallothecal sclerite (dps) in lateral view with posteromedian part weakly produced posterodorsad (Figs 6C, 15G, K); spoon-like sclerites (sps) hyaline and glabrous; both membranous sac-like lobes posterolaterally produced; distal dorsal lobe of endosoma (ddl) round, with membranous surface roughly lumpy (Fig. 15L).
Vestiture. Almost same as female except for the following characters. Head covered with short bent cream-yellow pubescence, and sparsely with long bent setae; pedicel with short vertical setae; first and second flagellomeres missing; neck without setae. Scutellum densely covered with short bent cream-yellow pubescence interspersed with long erect setae; trochanters, femora, and tibiae with long erect setae; connexivum with long vertical thick setae; abdominal venter with vertical setae; pygophore with oblique setae; paramere with long erect setae.
Measurements. All dimensions are given in mm. Diagnosis. Body shiny blackish brown; anterior pronotal lobe black or blackish brown with some rows of long bent griseous setae; posterior pronotal lobe blackish brown or brown and densely covered with short bent griseous setae somewhat interspersed with long griseous setae; scutellum black in basal half and dark brown or brown in lateral margin and apical half; abdominal sternites shiny sanguineous; laterotergites II-VI luteous, segmentally suffused with dark brown spots or blackish brown spots; laterotergite VII sanguineous.
In general appearance, Biasticus griseocapillus sp. nov. resembles B. confusus Hsiao et al., 1979, especially  Also, Biasticus griseocapillus sp. nov. is similar to B. taynguyenensis sp. nov. in the body color pattern, the proportion average length of the antenna segments, and the proportion average length of the visible labial segments. However, B. griseocapillus can be distinguished from the latter by a combination of the following characters: collar, anterior pronotal lobe, and posterior pronotal lobe covered with long bent griseous setae (in B. taynguyenensis short bent cream-yellow setae), and median process of pygophore (mpp) 0.2 × as long as wide, with apical margin weakly convex and emarginate medially, and with apicolateral corner slightly produced laterad and pointed (in B. taynguyenensis, 0.3 × as long as wide, with apical margin weakly and continuously concave, and with apicolateral corner distinctly produced posterolaterad and pointed). Description. Female description. Coloration. Body shiny blackish brown. Head dorsum (except anteclypeus, maxillary plate, and gena) black; anteclypeus, labrum, maxillary plate, and anterior region of gena brown; central fascia to head venter, and posterior region of gena pale luteous; first visible labial segment brown; second and third visible labial segments blackish brown; tips of first and second visible labial segments yellowish brown; area around lateral ocellus with reddish brown suffusion; a longitudinally elongated yellowish brown spot present between lateral ocelli. Base of scape brownish black; remaining of scape and pedicel, first and second flagellomeres blackish brown. Collar, anterolateral angles, anterior pronotal lobe, and anterior acetabulum black; posterior pronotal lobe, pleura, and thoracic sterna blackish brown; scutellum black in basal half and dark brown in lateral margin and apical half; stridulatory sulcus luteous; coxae and trochanters yellowish brown; intersecting area of fore coxae and fore trochanters luteous; femora, tibiae, and tarsi blackish brown. Corium and clavus darkish brown, apically brownish yellow; membrane bronzy brown, semihyaline. Hind wings faintly semi-hyaline. Abdominal mediotergites I+II to V reddish brown or sanguineous, somewhat suffused with blackish brown; mediotergite VI suffused with reddish brown and irregularly suffused with sanguineous; mediotergite VII and laterotergite VII to apex of abdomen sanguineous; abdominal sternite shiny sanguineous; laterotergites II-VI luteous, segmentally suffused with dark brown spots; laterotergite VII sanguineous. External genitalia sanguineous.
Vestiture. Body clothed with griseous setation. Head, except interocular sulcus and posterior margin of clypeus, covered with long erect setae; posterior margin of clypeus, head venter, anterolateral area of neck with short bent setae and sparsely with long erect setae; anteclypeus, labium, scape with a few short setae; pedicel, first and second flagellomeres covered with short erect to recumbent setae; dorsum of neck without setae. Collar, anterior margin of anterior pronotal lobe with dense bent pubescence; anterior pronotal lobe with some rows of long bent griseous setae; lateral area of anterior pronotal lobe with long erect setae; posterior pronotal lobe densely covered with short bent griseous setae somewhat interspersed with long griseous setae; lateral slope area and posterior apex of scutellum with dense short to long setae; posterior area of posterior pronotal lobe with long erect setae; pleura, thoracic sterna, and coxae with short bent setae; trochanters, femora, and tibiae with long erect setae; corium with bent griseous pubescence. Anterior margin of abdominal mediotergite I+II with some long slender erect yellowish brown setae; mediotergites and dorsal laterotergites sparsely covered with a few short vertical setae; abdominal sternites interspersed with long vertical setae; posterior margin of abdominal laterotergite VIII (AL8) with long erect slender setae; gonocoxa VIII (Gc8) with long slender bent setae; apex of external genitalia with long thick erect setae.
Male description. General external morphology similar to that of the female. Coloration. Almost similar to female but brighter than female. Gena brown in anterior half and luteous in posterior half; labium blackish brown; tips of first and second visible labial segments luteous. Collar, anterolateral angles, anterior pronotal lobe, and anterior acetabulum blackish brown; posterior pronotal lobe, pleura, and thoracic sterna brown; scutellum black in basal half and brown in lateral margin and apical half; stridulatory sulcus pale gray. Laterotergites II-VI pale luteous, segmentally suffused with blackish brown spots; laterotergite VII sanguineous. Pygophore ventrally orpiment-orange; paramere semi-hyaline, pale orange.
Structure. Almost similar to female except for the following characters. Scape 1.8 × as long as head and more than twice as long as pedicel; pedicel slightly longer than first flagellomere; second flagellomere missing; proportional length of scape, pedicel, and first flagellomere 3.5:1.6:1.4. Hemelytra surpassing apex of abdomen when fully closed, 0.9 × as long as body; Sc 0.8 × as long as hemelytron, and 1.5 × as long as R + M. Pygophore ovoid; median process of pygophore (mpp) broad and low, 0.2 × as long as wide, with apical margin weakly convex and emarginate medially, with apicolateral corner slightly produced laterad and pointed; paramere long, slender, clavate, somewhat curved medially, and apically subnodulose and round (Figs 6E, 18B-F). Aedeagus in dorsal view ovoid, dorsally sclerotized (Figs 6F, 18G, J) and in lateral view long and narrow (Figs 6G, 18H, L); articulatory apparatus (aa) in ventral view with basal plate arms relatively slender and jointly forming a U-shape, and in lateral view arched strongly (Figs 6G, I, 18H, I); dorsal phallothecal sclerite (dps) in lateral view with posteromedian part weakly produced posterodorsad (Figs 6G, 18L); spoon-like sclerites (sps) hyaline and glabrous; both membranous sac-like lobes posterolaterally produced; distal dorsal lobe of endosoma (ddl) round, with membranous surface covered with large hyaline prickles (Figs 6H, 18M).
Vestiture. Almost similar to female except for the following characters. Posterior margin of clypeus with short bent pubescence; anteclypeus and scape without setae. Collar and anterior margin of anterior pronotal lobe with short bent setae and some long bent setae; anterior pronotal lobe with some rows of long bent griseous setae; posterior pronotal lobe with bent griseous setae; scutellum with long slender erect setae abundantly, especially in lateral slopes; posterior apex of scutellum with a pinch of long slender erect and bent setae; pleura, thoracic sterna, and coxae with short bent setae, with a few long slender setae; trochanters sparsely with short bent pubescence and a few long setae; corium with bent pubescence. Pygophore ventrally covered with a few bent pubescence, more abundant laterally; paramere with a few long erect thick setae.  Diagnosis. Body shiny luteous; first visible labial segment and base of second visible labial segment luteous; apical 2/3 of second visible labial segment to third visible labial segment yellowish brown or brown; posterior pronotal lobe luteous; scutellum dark brown in basal half and luteous in apical half, with median pale brownish luteous portion; femora luteous with dark brown or yellowish brown suffusions at apex and sometimes at middle.
This species is most similar to Biasticus flavus (Distant, 1903) in general appearance, especially in coloration and color pattern of the pronotum, scutellum, and abdomen. However, the new species can be easily separated from the latter by a combination of the following characters: femora luteous with some dark brown or yellowish brown suffu- sions at apex and sometimes at middle (in B. flavus uniformly blackish brown) and abdominal sternites luteous without blackish brown or black suffusion (in B. flavus abdominal sternites luteous with blackish brown or black segmental transverse stripes laterally).
Description. Male description. Coloration. Body shiny luteous. Head dorsum, except antenniferous tubercle and neck, black; clypeus, antenniferous tubercle, and labrum brown; maxillary plate, gena, and head venter (except anterior margin of maxillary plate and anterior margin of gena) pale yellowish brown; anterior margin of maxillary plate and anterior margin of gena yellowish brown; first visible labial segment and base of second visible labial segment luteous; apical two-thirds of second visible labial segment to third visible labial segment yellowish brown or brown; a luteous suffusion present above upper margin of compound eye; a luteous stripe running along dorsal margin of compound eye and between postero-upper corner of compound eye and ocellus; area around lateral ocellus with yellowish brown suffusion; a longitudinally elongated luteous suffusion present between lateral ocelli; neck yellowish brown. Scape, except base, yellowish brown; base of scape blackish brown; pedicel, first and second flagellomeres dark brown. Collar, anterolateral angle, and posterior pronotal lobe pale luteous; anterior pronotal lobe, except lateral margin, shiny dark brown, sometimes with luteous suffusion centrally; lateral margin of anterior pronotal lobe, acetabulum, thoracic sterna, stridulatory sulcus, coxae, and trochanters pale luteous; coxae and trochanters sometimes with dark brown or yellowish brown spots; pleura, except lower half of propleuron, dark brown; lower half of propleuron pale luteous; scutellum dark brown in basal half and luteous in apical half, with median pale brownish luteous portion; femora luteous; fore femora apically dark brown, sometimes with dark brown or yellowish brown suffusion; mid and hind femora apically and medially yellowish brown; tibiae dark brown. Corium and clavus yellow or brownish yellow; membrane bronzy brown, semi-hyaline. Hind wings faintly semi-hyaline. Abdominal mediotergites, except posterior half of mediotergite VII, brownish yellow; posterior half of mediotergite VII luteous; abdominal sternites pale luteous; connexivum pale luteous, with segmentally dark brown suffusions. Pygophore ventrally luteous; paramere semi-hyaline, luteous.
Vestiture. Body clothed with cream-yellow setation. Head dorsum (except antenniferous tubercle, posterior base of clypeus, and gena) covered with short thick erect setae; area around antenniferous tubercle, posterior margin of clypeus, head venter, and lateral area of postocular area of head covered with short bent pubescence; head venter somewhat with a few long bent setae; maxillary plate without setae; first visible labial segment basally covered with a few erect setae; second and third visible labial segments without setae; scape with a few tiny erect setae; pedicel, first and second flagellomeres densely covered with short slender oblique setae. Anterior margin of collar densely covered with very short erect setae; dorsum of collar with bent cream-yellow pubescence; anterolateral angle and lateral region of collar with long thick erect setae, one of them placed at tip of anterolateral angle; pronotum and scutellum with long thick erect setae; lateral region of slopes of scutellum covered with long slender bent setae; posterior apex of scutellum with a pinch of long slender bent setae and long thick vertical setae; prosternum, except posterior margin, covered with long thick erect setae; posterior margin of prosternum, meso-and metasterna, pleura, and coxae abundantly covered with short bent pubescence. Corium densely covered with bent setae along anterior margin, centrally covered with short slender oblique setae. Abdomen sometimes with erect setae, slightly denser in posterior margin of abdomen; anterior margin of mediotergite I+II, anterior margin of sternite II, and lateral region of laterotergite II with very long slender erect setae; pygophore posteroventrally with some long erect setae and some bent slender setae; paramere with long thick erect setae.
Female description. General external morphology similar to that of the male. Coloration. Almost similar to male but slightly darker than male. Abdominal mediotergites, except posterior half of mediotergite VII, dark brown and darker backward; posterior half of mediotergite VII luteous; external genitalia pale luteous.
Vestiture. Almost similar to male. Abdominal laterotergite VIII (AL8) and tergite IX (AT9) with some long thick erect setae and with shorter setae; apex of abdomen with some very long thick erect setae.
Measurements. All dimensions are given in mm.