Lepidotrigona nitidiventris ( Smith, 1857 )

Attasopa, Korrawat, Packer, Laurence, Suttiprapan, Piyawan, Thanoosing, Chawatat & Bänziger, Hans, 2020, Description of the male of Lepidotrigona nitidiventris (Smith, 1857), redescription of the female holotype and additional morphological data on the workers (Hymenoptera: Apidae: Meliponini), Revue suisse de Zoologie 127 (1), pp. 119-128 : 120-126

Lepidotrigona nitidiventris ( Smith, 1857)

Figs 1-17

Holotype Worker (female): Figs 1-3

Type material examined: OUMNH; worker holotype; MALAYSIA; labelled as follows: “Holo-/ type”, “M. OPHIR/ 79”, “ Trigona nitidiventris ./ Smith” “ Tr. nitidiventris / Smith J. Pr. L. / Soc. T. 2 p 50/ Malacca M. Ophir” (see inset to Fig. 3 ) .

Diagnosis: Lepidotrigona nitidiventris is the type species of the genus and also the nominate species of the species group which comprises the largest species of the genus. Workers differ from those of L. ventralis and the L. terminata groups by a combination of body size (more than 5.5 mm) and apically expanded metatibia (spoon-like: as wide as approximately half its length, more than 0.46 times). In the other two groups the body length is usually less than 5.5 mm, and the metatibial ratio less than 0.45 times. Leipidotrigona nitidiventris also differs in the faintly yellow-tinged wings which are pale brownish grey in the other two groups. Lepidotrigona nitidiventris has robust hairs on the anterior and posterior margins of the mesoscutum and mesoscutellum, whereas the hairs are not robust on those areas in the L. ventralis group. Lepidotrigona nitidiventris can be differentiated from L. latipes by their brown tegula and black T2-T6, whereas they are yellowish brown and reddish brown, respectively, in L. latipes . The pale yellowish-brown vertex hairs in L. nitidiventris separate it from L. trochanterica , where those hairs are all black. L. palavanica differs from L. nitidiventris in being much smaller in body size and metatibial ratio.

Re-description of the species:

Structure: Body length 6.62 mm. Head wider than long (width 2.57 mm, length 1.95 mm); eye width (in side view) 0.67 mm; gena width 0.32 mm; interocellar distance 0.44 mm; ocellocular distance 0.38 mm; inner orbits slightly converging below, upper interorbital distance 1.51 mm, lower interorbital distance 1.46 mm; scape length excluding basal bulb 0.99 mm, with basal bulb 1.09 mm; 1st flagellomere length 0.16 mm; 2nd flagellomere length 0.24 mm, width 0.17 mm; 3rd flagellomere shorter than 2nd; malar space length 0.13 mm; length of longest hair on vertex 0.2 mm. Length of longest hair on mesoscutum 0.16 mm; length of longest hair on mesoscutellum 0.11 mm; forewing length 5.84 mm, width 2.32 mm; forewing diagonal 1.89 mm, length of 1st submarginal cell 0.41 mm, length of 2nd submarginal cell 0.87 mm; 1st recurrent vein before mid-length of posterior margin of 2nd submarginal cell. Metatibia length 2.51 mm, width 1.27 mm; metabasitarsus length 0.95 mm, width 0.66 mm.

Coloration of integument: Head black except as follows: apex of mandible dark brown; basal bulb and extreme base of scape, and base of F1 yellow; rest of flagellum dark brown. Mesosoma black except tegula, pronotal lobe, and sides of metanotum all brown; all legs black except all trochanters, procoxa, metacoxa ventrally, profemur ventrally, and posterior portion of metabasitarsus brown, tarsomeres 3 to 5 yellowish brown; wings hyaline to pale yellow, wing veins yellowish brown except C, R, M, and Rs brown. Metasomal terga black except basal depression and posterior margin of T1 whitish brown; metasomal sterna yellowish brown.

Pubescence: Facial hairs mostly plumose, densely appressed and whitish yellow; hairs of lower edge of labrum and mandible pale brown, hairs of vertex robust and pale yellowish-brown, longest hairs on vertex approximately 1/5 times as long as scape. Mesoscutum and mesoscutellum hairs minute yellowish white; hairs of anterior and posterior areas of mesoscutum and mesoscutellum robust, yellowish brown; mesoscutellum with some dark brown hairs intermixed, longest hairs on mesoscutum and mesoscutellum approximately 1/6th and 1/9th as long as scape, respectively; margins of mesoscutum and mesoscutellum with distinct band of short, plumose, scale-like yellow hairs, bands on mesoscutum wider anteriorly and posteriorly; mesepisternum, metepisternum, and pronotal lobe with whitish-yellow, plumose hairs, intermixed with long white hairs on mesepisternum ventrally; hairs on lateral surface of metanotum and propodeum plumose, yellowish white; metapostnotum bare; coxae and trochanters as well as ventral surface of profemur with yellowish-white hairs, rest of profemur with brown hairs intermixed with black hairs distally; tibiae with black hairs except metatibia with whitish-brown keirotrichia posteriorly; protarsi with brown hairs except probasitarsus with black hairs intermixed; meso- and metatarsi with black hairs intermixed with few brown hairs. T1 with minute, sparse, pale whitish-brown hairs except basal depression and posterior margin lacking hairs. Posterior margin of T2- T6 as well as visible portions of T5 and T6 with minute pale brown hairs intermixed with dark brown hairs on posterior half of T5 and T6; S1-S6 minute with sparse yellowish-brown hairs.

Surface sculpture: Head and mesosoma with fine, dense punctures, slightly larger on mesoscutellum; metapostnotum with larger crowded punctures all over, diameters 1.5-2 times those of head; all legs with sparse, shallow and fine punctures; lateral part of T1, posterolateral parts of T1-T4 and complete T5 and T6 with sparse shallow, fine punctures; posterior margin of T2-T4 and complete T5 and T6 with minute, shallow punctures; S1-S6 with fine shallow punctures all over.

Worker (female): Figs 4-6

Material examined: BCMU-LNW01 ; nest UP45; 2 workers; THAILAND, Tak Province., Umphang District ; 5.V.2011; leg. prep. H. Bänziger. – All remaining specimens with the same labels except as follows: BCMU-LNW 02; nest UP45; 2 workers; 19.VI.2012. – BCMU-LNW03 ; nest UP45; 2 workers; 21.III.2016. – BCMU-LNW04 ; nest UP88; 3 workers; 7.V.2016. – MHNG-LNW05 ; nest UP88; 1 worker; 7.V.2016 .

Variation: N=10, measured as range (average±SD). As in holotype except as follows:

Structure: Body length 5.69-6.56 (6.17±0.22) mm. Head width 2.58-2.87 (2.77±0.08) mm; head length 1.84- 2.03 (1.96±0.05) mm; eye width (in side view) 0.63- 0.68 (0.66±0.01) mm; gena width 0.3-0.42 (0.37±0.04) mm; interocellar distance 0.42-0.48 (0.45±0.02) mm; ocellocular distance 0.38-0.42 (0.4±0.01) mm; upper interorbital distance 1.51-1.61 (1.56±0.03) mm, lower interorbital distance 1.46-1.56 (1.52±0.03) mm; scape length excluding basal bulb 0.99-1.05 (1.03±0.02) mm, with basal bulb 1.09-1.2 (1.17±0.03) mm; 1st flagellomere length 0.16-0.18 (0.17±0.01) mm; 2nd flagellomere length 0.2-0.23 (0.21±0.01) mm, width 0.16-0.18 (0.17±0.004) mm; malar space length 0.14- 0.15 (0.14±0.005) mm; length of longest hairs on vertex 0.2-0.25 (0.21±0.02) mm. Length of longest hairs on mesoscutum 0.17-0.22 (0.19±0.01) mm; length of longest hairs on mesoscutellum 0.13-0.18 (0.15±0.02) mm; forewing length 5.73-6.27 (6.05±0.18) mm, width 2.35-2.52 (2.21±0.74) mm; forewing diagonal 1.94- 2.03 (1.98±0.03) mm, length of 1st submarginal cell 0.44-0.48 (0.46±0.01) mm, length of 2nd submarginal cell 0.84-0.95 (0.89±0.03) mm. Metatibia length 2.51- 2.67 (2.6±0.05) mm, width 1.23-1.32 (1.27±0.02) mm; metabasitarsus length 0.95-1.07 (1±0.04) mm, width 0.67-0.75 (0.7±0.02) mm.

Coloration of integument: Tegula, wing veins M, Rs, and stigma slightly paler yellow than those of the holotype; mesoscutellum dark brown, sometimes with a brown spot posteromedially; tarsomeres 3 to 5 sometimes dark brown. T1 laterally with two large black triangular spots which occasionally are in contact with each other, rest of T1 sometimes light brown; metasomal sterna vary in darkness of brown.

Pubescence: Hairs of vertex slightly darker than those of the holotype, sometimes intermixed with dark brown hairs. Metasomal sternal hairs sometimes paler than those of the holotype.

Surface sculpture: Punctures on metasomal terga vary in density, otherwise as in holotype.

Male: Figs 7-17

Material examined: BCMU-LNM01 ; nest UP88; 7 males; THAILAND, Tak Prov., Umphang Distr ; 7.V.2016; leg. prep. H. Bänziger; caught leaving the nest [not swarming]. – MHNG-LNM02 ; nest UP88; 1 male; Tak Prov., Umphang Distr ; 7.V.2016; leg. prep. H. Bänziger; caught leaving the nest [not swarming].

Male terminalia and associated sterna: Dissected from five males ( BCMU-LNM 01) with the following codes: GP 3200, GP 3201, GP 3205, GP 3365, GPKA 88.

Diagnosis: Males differ from the males of L. terminata and L. ventralis group by their overall larger size, shape of the metatibia and of S5 and S6 as follows: male of L. nitidiventris with expanded, triangular metatibia with apical margin straight, with a black comb near apicodorsal area (missing in other species where males are known); metatibial hairs dark brown to black ( Figs 7, 8 ). Metatibia of other species simple, rounded apically, without comb, with hairs grey to brown or intermixed with few dark brown hairs. S5 of L. nitidiventris has long protruding apical-lateral lobes, but no subapical lobes ( Fig. 11 ), whereas S5 of other known males of the genus have short to very short lateral lobes, two distinct subapical lobes, and strong apical setae. S6 of L. nitidiventris with two deep subapical emarginations with long, narrow apicalmedial lobes ( Fig. 12 ), S6 of other known males of the genus do not have or have only weakly produced subapical emarginations, and short apical-medial lobes. Genital capsule of L. nitidiventris bilaterally symmetrical ( Fig. 16 ), asymmetrical in the known species that belong to the L. ventralis group.

Description: N=8, measured as range (average±SD). As in the worker holotype except as follows:

Structure: Body length 6.19-6.98 (6.56±0.3) mm. Head width 2.4-2.62 (2.55±0.07) mm; head length 1.81- 2 (1.89±0.06) mm; eye width (in side view) 0.62-0.72 (0.68±0.04) mm; gena width 0.28-0.37 (0.31±0.03) mm; interocellar distance 0.4-0.55 (0.49±0.05) mm; ocellocular distance 0.3-0.33 (0.33±0.01) mm; inner orbits converging below, upper interorbital distance 1.49-1.56 (1.52±0.02) mm, lower interorbital distance 1.04-1.11 (1.07±0.02) mm; scape length excluding basal bulb 0.75-0.78 (0.78±0.01) mm, with basal bulb 0.88-0.95 (0.93±0.02) mm; 1st flagellomere length 0.14- 0.16 (0.15±0.01) mm; 2nd flagellomere length 0.28- 0.3 (0.3±0.01) mm, width 0.16-0.17 (0.16±0.004) mm; malar space length 0.02-0.03 (0.03±0.003) mm; length of longest hairs on vertex 0.33-0.43 (0.37±0.04) mm. Length of longest hairs on mesoscutum 0.2-0.24 (0.22±0.01) mm; length of longest hairs on mesoscutellum 0.16-0.18 (0.17±0.01) mm; forewing length 5.6-6.05 (5.86±0.14) mm, width 2.05-2.18 (2.12±0.04) mm; forewing diagonal 1.78-1.97 (1.86±0.06) mm, length of 1st submarginal cell 0.43-0.48 (0.45±0.02) mm, 2nd submarginal cell length 0.77-0.83 (0.8±0.02) mm. Metatibia length 2.48- 2.66 (2.57±0.07) mm, width 1.08-1.2 (1.16±0.03) mm; metabasitarsus length 0.7-0.77 (0.73±0.02) mm, width 0.48-0.53 (0.51±0.02) mm. Apex of S1 and S2 entire, S3 with small narrow emargination apicomedially; apical margin of metatibia flat diagonally (not rounded) forming a triangular-shaped metatibia, and with a black metatibial comb on the apex near the dorsal margin.

Coloration of integument: Yellowish-brown area on F1 slightly darker than in holotype. Mesosoma black except tegula and pronotal lobe light brown, mesoscutellum seldom with yellowish-brown spot posteromedially; procoxa and proximoventral area of profemur brown, protrochanter and protarsus yellowish brown, rest of fore leg black; mid and hind legs black except mesotrochanter, and meso- and metatarsomeres 4-5 yellowish-brown, metatrochanter and ventral area of meso- and metafemurs brown, anterodistal and posterior area of metatibia and metabasitarsus sometimes brown, hyaline wings pale yellowish, slightly more brownish tinged than in workers, wing veins yellowish brown except C and R, dark brown. Metasomal terga black except basal depression of T1 brownish white or vary to light brown, T6 and T7 sometimes dark brown; S1-S7 light brown.

Pubescence: Hairs of vertex long whitish brown, longest hairs approximately half of scape length; scape with thin white hairs medioventrally. Hairs of mesoscutum and mesoscutellum mostly whitish brown with brown hairs intermixed on mesoscutellum posteriorly, the longest hairs on mesoscutum and mesoscutellum approximately 3/10 and 2/9 as long as scape, respectively; posterolateral margin of mesoscutum with thinly scattered whitishyellow plumose hairs, which vary in density, sometimes to the point that the plumose hairs are missing altogether laterally; pronotal lobe, mesepisternum, metepisternum, lateral surface of propodeum, and metanotum with short, plumose, yellowish-white hairs intermixed with yellowish-white simple hairs, the simple hairs longest on mesepisternum ventrally; coxae and trochanters with long white hairs; femurs with white hairs ventrally and with short dark brown hair dorsodistally; protarsi with light brown hairs intermixed with few dark brown hairs; pro-, mesotibiae, and metatarsus with dark brown hairs intermixed with few whitish-brown hairs; metatibia with black or sometimes dark brown hairs, and with a black comb restricted to the apical angle, as well as with yellowish-white keirotrichia posteriorly. Metasomal tergal hairs as those of the holotype except lateral and posterior area of T4-T5, T6 and T7 posteriorly with black hairs; S1-S3 with short brown hairs.

Surface sculpture: As for the holotype but punctures smaller and denser on mesoscutum.

Terminalia and associated sterna: S4 emarginate apicomedially forming an apex with two broad shallow lobes, S4 gradulus almost touching anterior margin of sternum anteromedially; area posterior to gradulus with short hairs, the hairs denser on lateral lobes, and with a brown spot laterally ( Fig. 10 ). S5 with long protruding apicolateral lobe posterolaterally oriented, and with deep emargination apicomedially, gradulus transverse medially, touching anterior margin of sternum; S5 with hairs on posterior area from gradulus, longer on posterior margin and apicolateral lobe; S5 brown marked laterally, darker on the apicolateral lobe ( Fig. 11 ). S6 biconcave with long apicomedial lobe, narrowing distally with spatulate apex, apical emarginations with long hairs ( Fig. 12 ). S7 convex apicomedially and bisinuate apicolaterally, with small asymmetrical subapicolateral lobes, the left lobe appearing to be slightly more protruding than the right one ( Fig. 13 ). Gonostylus longer than penis valve, tip expanded widest at approximately apical 1/6, genital capsule and apical 1/3 of gonostylus light brown except penis valve and the remainder of gonostylus black. Penis valve narrow, first weakly curved ventrally mainly at mid-length, slightly curved lateroventrally towards apex ( Figs 14-17 ).

Figures

Figs 1-6. Lepidotrigona nitidiventris, worker. (1-3) The Malaysian holotype, including its label at the bottom left of (3). (4-6) Thai worker, BCMU-LNW04 (HB-W1). Dorsal habitus (1, 4), lateral habitus (2, 5), head, frontal view (3, 6). Scale bars: 1 mm.

Figs 7-9. Lepidotrigona nitidiventris, male, BCMU-LNM01 (HB-M1). Dorsal habitus (7), lateral habitus (8), head, frontal view (9). mt.cmb – metatibial comb. Scale bars: 1 mm.

Figs 10-17. Lepidotrigona nitidiventris, male terminalia and associated sterna, BCMU-LNM01 (HB-M1), GPKA88. (10-13) S4-S7, ventral view. (14-17) Genital capsule. Dorsal aspect (14), ventral aspect (15), lateral aspect (16), caudal aspect (17). al.lb – apicolateral lobe, am.lb – apicomedian lobe, grdl – gradulus, l.gnst – left gonostylus, r.pn.vl – right penis valve, sa.em – subapical emargination.All figures are shown at the same scale. Scale bar: 0.5 mm.