Lepidotrigona satun Attasopa and Bänziger n. sp. Figs. 2: A1–4, 3: A1–A4 & 4–6 Diagnosis. Lepidotrigona satun is a member of the “ ventralis ” species group based primarily on size: body and forewing length each less than 5 mm. It is the only species in the group known from the lower peninsula of Thailand. Males can be differentiated from those of the other two species of the “ ventralis ” group confirmed as occurring in Thailand (L. flavibasis and L. doipaensis) based upon external morphology as follows: margin of mesoscutum of L. satun with plumose, scale-like, yellow hairs (Fig. 4: A) (no such hairs in the other two species). S4 of L. satun is angularly emarginate apicomedially (Fig. 2: A1) (convex medially and bisinuate laterally in L. flavibasis, slightly concave in L. doipaensis). The apicosubmedial lobes of S 5 in L. satun are apically rounded each with 4–7 thick, long setae (Fig. 2: A2) (the lobes are pointed in the other two species and bear only 1–2 setae which are very short in L. flavibasis (Fig. 2: B2) or with one very long and, if present, a second much shorter in L. doipaensis (Fig. 2: C2)). S5 gradulus does not touch the antecosta in L. satun (Fig. 2: A2) whereas it does touch it in the other two species, briefly in L. flavibasis (Fig. 2: B2) and extensively in L. doipaensis (Fig. 2: C2). Males can also be differentiated from those of these other two species because of the very short malar space of L. satun, at most 0.16 times as long as the length of the first flagellomere whereas in the other two species it is at least 0.27 times as long as the first flagellomere. The ratio of the forewing diagonal to the length of the 2nd submarginal cell also varies among the three: it is largest (ḵ2.3) in L. satun, but at most 2.11 in the other two species (shortest - 1.94 to 2.05 - in L. doipaensis and intermediate - 2.05 to 2.11 - in L. flavibasis) (see Table 1). The genitalia are also very different in the three species (see below and Fig. 3). Workers of L. satun can be differentiated from all others in the L. ventralis species group, except L. flavibasis, due to the coloration of the pubescence. Lepidotrigona satun has dark hairs on the tibiae and pale yellowish brown to pale brown hairs on the vertex and mostly pale hairs (except posteriorly) on the mesoscutellum; no other member of the ventralis species group (except L. flavibasis) has this combination: L. hoozana and L. ventralis have some or entirely (respectively) whitish hairs on the metatibia, whereas the other four species have brown to black hairs; L. arcifera has pale hairs on the pro- and mesotibiae whereas L. satun, L. flavibasis and L. doipaensis have dark hairs; L. doipaensis has black hairs on the vertex and mesoscutellum, whereas L. flavibasis and L. satun do not have these hairs black but yellowish grey or variously pale to dark brown, respectively; the thickest of these hairs are about 0.007 mm, 0.003 mm and 0.005 mm wide, respectively. Workers of L. satun and L. flavibasis can be readily differentiated by the ratio of lengths of the metatibia and 2nd submarginal cell, at least 1.21 in L. satun, at most 0.98 in L. flavibasis and intermediate 1.05–1.09 in L. doipaensis. There are additional morphometric differences among the three species (Table 1). Description. Holotype Male. Structure: Body length 4.67 mm. Head wider than long; head width 1.77 mm; head length 1.31 mm; eye width (in side view) 0.51 mm; gena width 0.18 mm; interocellar distance 0.31 mm; ocellocular distance 0.17 mm; inner orbits strongly converging below, upper interorbital distance 0.98 mm, lower interorbital distance 0.68 mm; scape length excluding basal bulb 0.48 mm, with basal bulb 0.57 mm; 1 st flagellomere length 0.09 mm; 2nd flagellomere length 0.17 mm, width 0.13 mm; 3rd subequal to 2nd; 4th slightly longer than broad; malar space length 0.01 mm; mandible with subapical tooth. Forewing length (measured from humeral angle to apex) 4.03 mm, width 1.52 mm; forewing diagonal 1.1 mm, length of 1 st submarginal cell 0.35 mm, 2nd submarginal cell length 0.47 mm, vein Rs reaching stigma, 1 st recurrent vein at approximately mid-length of 2nd submarginal cell. Metatibia length 1.34 mm, width 0.52 mm; metabasitarsus length 0.51 mm, width 0.34 mm. Metasomal sterna and terminalia are described from paratypes in a separate section below. Coloration of integument: Head black except as follows: dorsal surface of scape, most of pedicel, proximal half of F1, and small marks towards base and apex of mandible dark brown; supraclypeal area and clypeus brown; labrum, most of mandible, ventral surface of scape, apical mark on pedicel and the rest of F1 yellowish brown. Mesosoma brown except pronotal lobe, mesoscutum, metepisternum and sides of metanotum black and metanotum medially yellowish brown; fore and mid legs pale brown except coxae, trochanters proximally and femora dorsally brown; hind leg brown except tarsus yellowish brown; wings hyaline to pale brown, wing veins and stigma pale brown except veins C, R, M, Rs, and R1 brownish black. Metasomal terga amber brown except T1 with semicircular brown band darker towards sides on disc, basal depression translucent, posterior marginal zone translucent amber, T4–T5 brown; S1 and S2 anteriorly whitish translucent, S3 with lateral brown spot. Pubescence: Most of face from lower margin of vertex to apex of clypeus with short plumose dense appressed yellowish white hairs; labrum, ventral scape, most portion of genal area, and lower edge of mandible with pale yellowish brown hairs longest at apex of labrum and lower mandible; ventral surface of scape with very short pale brown hairs; vertex with erect long pale yellowish brown hairs, longest hairs of vertex approximately one half as long as scape. Mesoscutum with long and very short pale yellowish brown hairs, the longest hairs approximately one quarter as long as scape; margins of mesoscutum with distinct band of short plumose scale-like yellow hairs interrupted anteromedially and posteriorly; mesoscutellum with pale yellowish brown hairs, progressively longer from anterior to posterior; mesepisternum, metepisternum and metanotum with pale brown hairs, somewhat darker anteroventrally on mesepisternum; posteroventral area of mesepisternum with long white hairs, pronotal lobe and mesepisternum anterodorsally with yellow plumose scale-like hairs; metapostnotum without hairs, lateral surface of propodeum with minute dense white hairs; coxa and trochanter of all legs with long pale brownish white hairs, ventral surface of all femora with pale brown hairs, remaining femora with pale brown hairs intermixed with dark brown hairs, protibia with pale brown hairs intermixed with few short dark brown hairs, the dorsal and anterior mesotibia with dark brown hairs, rest of mesotibia with pale yellowish brown hairs, metatibia dorsally with hairs variable, mostly brown, sometimes dark brown or greyish yellow, or intermixed; protarsus with yellowish brown hairs, meso- and metatarsi with yellowish brown hairs intermixed with few dark brown hairs, posterior surface of metatibia with short yellowish brown keirotrichia. Posterolateral margin of T1 and posterior and lateral parts of T2–T4 with minute sparse pale brownish white hairs; T3–T6 laterally with fine pale brown hairs progressively longer from T3–T6; T7 with pale brown hairs most dense on posterior margin, the longest hairs as long as the longest hairs of T6. Surface sculpture: Head and most of mesosoma with fine dense punctures; metapostnotum with coarse crowded sharp-edged punctures, diameters 2–2.5 times those of mesoscutum; all legs with fine sparse punctures; metasomal terga shining, T1 with few coarse punctures on posterolateral brown band, T2–T7 with few fine shallow punctures restricted to the posterior margin; metasomal sterna somewhat shining with sparse fine shallow punctures. Description. Paratype Males , measured as range (Average±SD, n=10). As in the holotype except as follows: Structure: Body length 4.33–4.85 (4.58±0.15) mm. Head width 1.72–1.77 (1.75±0.02) mm; head length 1.24– 1.34 (1.32±0.03) mm; inner orbits converging below, upper interorbital distance 0.94–1.01 (0.97±0.03) mm, lower interorbital distance 0.67–0.73 (0.69±0.02) mm; eye width 0.48–0.54 (0.52±0.02) mm; gena width 0.14–0.18 (0.17±0.02) mm; interocellar distance 0.28–0.31 (0.29±0.01) mm; ocellocular distance 0.1 8–0.22 (0.2±0.01) mm; scape length excluding basal bulb 0.47–0.52 (0.49±0.01) mm, with basal bulb 0.56–0.59 (0.58±0.01) mm); 1 st flagellomere length 0.09–0.11 (0.1±0.01) mm; 2nd flagellomere length 0.15–0.17 (0.16±0.01) mm, width 0.12– 0.14 (0.13±0.004); 3rd subequal to 2nd; 4th slightly longer than broad; malar space length 0.01–0.02 (0.01±0.002) mm. Forewing length 3.94–4.09 (4.01±0.05) mm, width 1.47–1.52 (1.49±0.02); forewing diagonal 1.09–1.18 (1.15±0.03) mm, length of 1 st submarginal cell 0.3–0.34 (0.32±0.01) mm, 2nd submarginal cell length 0.46–0.52 (0.49±0.01) mm. Metatibia length 1.34–1.43 (1.39±0.03) mm, width 0.47–0.53 (0.5±0.02) mm. Metabasitarsus length 0.47–0.55 (0.5±0.03) mm, width 0.29–0.33 (0.31±0.01) mm. Coloration of integument: Ventral scape usually yellowish brown rarely brown on distal half, yellowish brown area on pedicel and 1 st flagellomere varies in size, position, and sometimes brown; pale marking on disc of tegula varies in size, seldom absent; mesepisternum sometimes dark brown; propodeum sometimes dark brown or more or less black; all coxae sometimes brown, femora and tibiae vary in darkness of brown; semicircular brown band of T1 varies slightly in width, sometimes darker than other terga; T2–T7 sometimes darker than in the holotype. Pubescence: Long hairs on vertex, mesoscutum and mesoscutellum sometimes slightly paler and longer than the holotype; yellow plumose scale-like hairs on mesepisternum vary in density; minute hairs on visible portion of metasomal terga vary in length and density. Surface sculpture: Fine shallow punctures on T2–T7 vary in density. Description. Paratype Workers , measured as range (Average±SD, n=10). As in the holotype except for usual sexual dimorphism in flagellomeres, metasomal segment number, presence of corbicula, terminalia, and as follows: Structure: Body length 3.94–4.39 (4.16±0.15) mm. Head wider than long; head width 1.76–1.85 (1.81±0.03) mm; head length 1.38–1.45 (1.41±0.02) mm, inner orbits slightly diverging for upper half, converging below, upper interorbital distance 1.08–1.13 (1.11±0.02) mm, lower interorbital distance 0.97–1.03 (0.99±0.02) mm; eye width 0.41–0.48 (0.45±0.02) mm; gena width 0.2–0.27 (0.25±0.02) mm; interocellar distance 0.2 7–0.32 (0.29±0.02) mm; ocellocular 0.26–0.3 (0.28±0.01) mm; scape length excluding basal bulb 0.62–0.67 (0.65±0.01) mm, with basal bulb 0.72–0.75 (0.74±0.01) mm; 1 st flagellomere length 0.11–0.13 (0.12±0.01) mm; 2nd flagellomere length 0.1– 0.13 (0.11±0.01) mm, width 0.11–0.13 (0.13±0.01); 3rd approximate subequal to 2nd; 4th as long as broad; malar space length 0.08–0.11 (0.09±0.01) mm; mandible with two subapical teeth. Forewing length 3.97–4.09 (4.04±0.04) mm, width 1.51–1.54 (1.52±0.01) mm; forewing diagonal 1.15–1.19 (1.17±0.01) mm, length of 1 st submarginal cell 0.3–0.34 (0.32±0.01) mm, 2nd submarginal cell length 0.46–0.52 (0.49±0.01) mm, 1 st recurrent vein at approximately before middle-length of 2nd submarginal cell. Metatibia length 1.45–1.51(1.49±0.02) mm, width 0.6–0.63 (0.62±0.01) mm; metabasitarsus length 0.57–0.66 (0.61±0.03), width 0.38–0.41 (0.4±0.01). S1 emarginate posteromedially, posterior margin of S2–S5 with shallow broad emargination, S6 entire. Coloration of integument: Labrum, scape basal bulb, distal and basal marks on scape and 1 st flagellomere medially light brown; rest of antenna dark brown (scape and pedicel sometimes black). Mesosoma black except mesoscutellum and tegula dark brown with paler brown disc; all legs black to dark brown, probasitarsus dark to yellowish brown, apex of metatibia and metabasitarsus sometimes brown, tarsi of all legs light brown except slightly darker posteriorly. Semicircular brown band on disc of T1 usually wider laterally than in male; T2–T5 black, sometimes pregradular area of T2 brown; T6 usually black except apex pale, seldom wholly pale brown. Pubescence: Plumose appressed hairs on face absent from upper frons to vertex, occiput and upper genal area; scape ventrally with few very short pale brown hairs; vertex with erect pale brown hairs shorter and slightly darker than those of male, mesoscutum with sparse short pale brown hairs, medial interruption absent on distinct yellow band; mesoscutellum with long pale yellowish grey hairs variously intermixed with pale to dark brown (but not black) hairs, the thickest hairs about 0.005 mm wide (about 1/10 of the gonostylar width of the male), mesepisternum with fine brown hairs, with long white hairs ventrally, patches of yellow plumose scale-like hairs on mesepisternum anterodorsally and pronotal lobe usually larger than in males; metepisternum and lateral surface of propodeum with fine short pale yellowish white hairs (sometimes yellowish brown); all femora dorsally with dark brown hairs though paler posteriorly, with white (sometimes pale brown) hairs ventrally; pro- and mesotibiae with dark brown hairs intermixed with pale brown hairs posteriorly, metatibia with dark brown hairs dorsally, tips of hairs slightly paler, ventrally with paler hairs intermixed with a few dark hairs, posteriorly with whitish brown keirotrichia; all basitarsi with dark brown intermixed with yellowish brown hairs, remaining tarsomeres with yellowish brown hairs sometimes intermixed with few brown hairs; T1–T4 with minute hairs slightly darker than in male; T3–T6 towards sides with dark brown hairs; S1–S6 with minute pale brown hairs progressively longer from anterior to posterior on each sternum. Surface sculpture: Punctures on mesoscutellum, metanotum, and metepisternum slightly larger than on rest of mesosoma; all legs mostly with fine punctures intermixed with few coarse punctures, all femora with punctures similar to those of metapostnotum though slightly smaller; anterior surface of metatibia usually shining for ~apical 2/3, shining area varies in size. Male Metasomal Sterna and Genitalia. In the following, description of genitalic features is based upon dissections of paratype males from all four nests (see material examined). S4–S7 weakly sclerotized except S4 posterolaterally, S5 laterally and posteriorly brown (Fig. 2: A1–4); S4 angularly emarginate apicomedially, depth of emargination ~0.33 times length of sternum, emargination separating two broadly rounded lobes, more strongly sclerotized area of S4 with fine dense hairs, longest and densest lateral to apex of lobe; gradulus of S4 weakly convex close to anterior margin of S4 (Fig. 2: A1); S5 with four apical lobes, long submedian lobes separated by deep U-shaped emargination, depth of emargination ~0.63 times medial length of S5, short lateral lobe separated from medial lobe by shallow concavity, medial lobes bearing ~4–7 thick setae apically, gradulus of S5 transverse medially, near anterior margin (Fig. 2: A2); S6 apical margin weakly produced medially, weakly concave laterally (Fig. 2: A3); S7 1.56 times as wide as long, apical margin convex throughout (Fig. 2: A4). Genital capsule light brown except black for apical 3/5 of penis valve; penis valve curved ventrally, somewhat hook-like, curvature strongest on basal third to half, then almost straight, the right valve tends to overlap the left one somewhat and its apex is slightly posterior to that of the left valve. Gonostylus not sclerotized, narrow, at least 12 times as long as wide (0.75–0.78 mm long and 0.044–0.058 mm wide), slightly expanded for apical 1/3, medial surface setose on apical half, hairs denser towards apex, lateral surface with few short hairs in apical half (Fig. 3: A1–4). Etymology. The specific epithet refers to the province in Thailand where the species was collected; it is a noun in apposition. Material examined. Holotype. (Nest TB 2, male, to be deposited in QSBG) labelled as follows: “Thaleban Nat. Park/ Satun Prov., 100 m / 27.iv.2017 / ex nest TB2/ S. THAILAND / H. Bänziger leg prep det”, “ HOLOTYPE ”. Paratypes. All bearing labels that state “ PARATYPE ” and the same locality as those of the holotype except dates and nests as follows: Measured paratypes (included in description and Table 1) labelled as follows: 26.iv.2017 (Nest TB1, 1 worker); 27.iv.2017 (Nest TB1, 1 male); 27.iv.2017 (Nest TB2, 3 males, 3 workers); 27.iv.2017 (Nest TB3, 3 males, 3 workers); 27.iv.2017 (Nest TB4, 3 males, 2 workers); 29.iv.2017 (Nest TB1, 1 worker). Non-measured paratypes: 27.iv.2017 (Nest TB1, 2 males), 26.iv.2017 (Nest TB1, 2 workers), 29.iv.2017 (Nest TB1, 2 workers), 27.iv.2017 (Nest TB2, 17 males, 14 workers; 27.iv.2017 (Nest TB3, 7 males, 2 workers); 27.iv.2017 (Nest TB4, 11 males and 2 workers). Genitalia examined: GP 3304, 3305, 3306, 3308, 3309, 3310, 3311, same nest as holotype; GP 3307, 3312, 3313, 3314, 3315, 3316, 3317, paratypes of nest TB4; GP 3318, 3319, 3320, 3321, 3322, paratypes of nest TB3; GP 3323, paratype of nest TB1.