Tetragonula (Tetragonula) malaipanae, Engel & Michener & Boontop, 2017

Engel, Michael S., Michener, Charles D. & Boontop, Yuvarin, 2017, Notes on Southeast Asian Stingless Bees of the Genus Tetragonula (Hymenoptera: Apidae), with the Description of a New Species from Thailand, American Museum Novitates 2017 (3886), pp. 1-17 : 5-11

Tetragonula (Tetragonula) malaipanae , new species

Figures 1–3

DIAGNOSIS: The species generally agrees with the subgeneric characterization as presented by Sakagami (1978). Worker dark but paler than Tetragonula laeviceps ( Smith, 1857) , T. pagdeni ( Schwarz, 1939) , and T. pagdeniformis ( Sakagami, 1978) (figs. 1A, 1B), clypeus yellowish (fig. 1C), legs partly or wholly red brown or testaceous (fig. 1A). Size similar to that of T. testaceitarsis ( Cameron, 1901) (likely senior synonym of T. valdezi [ Cockerell, 1918]), larger than T. laeviceps (as restricted by Rasmussen and Michener, 2010), T. pagdeni , and T. pagdeniformis (see Discussion, below). Mesoscutum with pale pubescence not or weakly banded (fig. 1B), sublateral bare bands not or scarcely recognizable. Setae of body largely pale, but those of vertex, especially behind ocelli, blackish or sometimes dusky. Mean metatibial length 1.81 mm, mean forewing length including tegula 4.58 mm, mean head width 1.90 mm. Male generally colored as in worker (fig. 2), with S5 lacking gradulus (fig. 3C), apical process of S6 long and parallel sided (fig. 3D), S7 and T7 sharply pointed apically (figs. 3B, 3E); genitalia with penis valves and gonostyli directed posteriorly (figs. 3F, 3H), sclerotization probably representing gonobase across base (figs. 3F, 3H).

DESCRIPTION: Worker. Body length 3.92 mm (3.50–4.70 mm); forewing length, including tegula, 4.58 mm (4.40–4.70 mm); head length from anterior margin of clypeus to summit of vertex, in facial view 1.42 mm (1.40–1.50 mm); head width 1.91 mm (1.75–2.00 mm); metatibia length 1.82 mm (1.63–1.88 mm); forewing diagonal from base of vein M to base of crossvein r-rs at margin of pterostigma 1.31 mm (1.23–1.38 mm). Scape (excluding basal bulb) more than half as long as compound eye; flagellomere IV slightly broader than long. Ocelloccipital distance over half OD, ocellocular distance less than interocellar distance. Genal area widest at about upper third of compound eye, and narrower than compound eye in profile. Metatibia and metabasitarsus shaped as usual in this group (see Sakagami, 1978: fig. 2); basal sericeous area at base of inner surface of metabasitarsus well defined, reaching to middle of metabasitarsus [variable, not attaining middle or extending beyond middle]. Metasoma short, about as wide as head, widest at T2 and T3, remaining terga progressively much narrower and largely telescoped into preceding segments. Cuticular surface polished and shining with few minute punctures or setal bases.

Head black, the following parts yellow testaceous [to reddish testaceous or pale yellowish brown]: clypeus except dusky upper and upper lateral margins [entire clypeus commonly yellowish], supraclypeal area [sometimes dusky or blackish], mandible except blackish apex and extreme base, and labrum. [Lower genal area and hypostomal area behind mandibular base sometimes weakly brownish, grading into black background]. Antenna yellowish [to reddish] testaceous, flagellum blackish [or dusky] on upper surface, on lower surface part of each flagellomere dusky [or not]. Thorax black except pronotum dark brown [to blackish], pronotal lobe dusky testaceous [to black], mesoscutellum brownish [or black], [mesepisternum sometimes brownish black], anterolateral part of mesepisternum brown [to black]. Legs (including coxae and trochanters) reddish brown, meso- and metatibiae and tarsi dark reddish brown [or rarely legs testaceous or legs blackish brown, sometimes only mid and hind legs dark, inner surface of metatibia and metatarsus and often basal part of metafemur reddish brown]. Tegula dusky testaceous. Wings clear, faintly dusky, veins and pterostigma blackish. Metasoma with T1 dusky brown [brown], anterior surface largely testaceous; T5 and T6 [sometimes on T6] testaceous [brown or dusky]; T2 and T4 [sometimes also T5] brownish black, posterior margins paler translucent [posterior part of T1 sometimes similarly dark]. [Sometimes, especially specimens from nests 6 and 9, with all terga testaceous, posterior ones darker than anterior ones]. Metasomal sterna testaceous [brown, sometimes slightly dusky].

Pubescence decumbent and pallid except as otherwise noted, mostly ochraceous; clypeus without erect simple setae, even lower margin without such setae. Setae of face short (0.5 OD), plumose, rather dense but not hiding surface, particularly sparse and thin on lower paraocular area, whitish, those of frons [or upper half of frons] brownish to yellowish and hence inconspicuous in certain views; erect setae of scape absent except for exceedingly short ones; longer setae (1 OD) of vertex, especially behind ocelli, blackish or dusky; short pale setae of mesoscutum weakly [or not recognizably] banded. When recognizable, median asetose band (“G1” of Sakagami, 1978) narrow, extending full length of mesoscutum except anterior extremity, G2 similarly narrow anteriorly but broadening and diverging posteriorly, G3 (lateral asetose band) poorly defined, especially on anterior half of mesoscutum [not recognizable except in some fresh, clean specimens]; longer, erect setae of mesoscutum (2 OD) pale or in certain illuminations dusky; fringe of long setae (up to 3 OD) on posterior margin of mesoscutellum ochraceous, with longest setae (3–4 OD) sometimes appearing dusky; metepisternum, side of propodeum, and anterior half of mesepisternum covered with dense white setae hiding surface [those of mesepisternum sometimes ochraceous]; some setae of outer surfaces of meso- and metatibiae and basitarsi dusky [commonly most setae of these parts, including large simple discal setae of corbicula, black or blackish]; anterior fringe of corbicula with a few [nearly all] setae dusky or blackish. T1 smooth and asetose; T2 to T5 smooth and asetose except for preapical very sparse bands, that of T2 consisting of only a few minute ochraceous setae, those of following terga with progressively more and longer setae, a few of those of T4 reaching beyond apical margin of tergum, those of T5 and T6 still longer, but all small and not conspicuous; setae of sterna denser and longer, almost white.

Male. Agrees with description of worker except for variation noted above in brackets, in measurements provided, and as follows (except for measurements, description based on male collected from nest 4 on 17 September 2007): body length 4.50 mm; forewing length, including tegula, 4.45 mm (4.40–4.50 mm); head length (measured as for worker) 1.40 mm; head width 1.78 mm; metatibia length 1.46 mm (1.43–1.48 mm); forewing diagonal (measured as for worker) 1.26 mm (1.25–1.27 mm).

Scape (excluding basal bulb) slightly less than half as long as compound eye. Flagellomere 4 (also 2–10) longer than broad. Ocelloccipital distance less than half OD; ocellocular distance about half of interocellar distance. Metatibia widest at about apical third, narrowed at apex, without plumose setae (fig. 3A). Metasomal T7 without Y-shaped ridge, apex broadly rounded (fig. 3B); S5 short, without noticeable gradulus, with shallow, broad, midapical emargination (fig. 3C); apical process of S6 slender, parallel sided (fig. 3D); terminalia as illustrated in figures 3D–3H; unbroken, weakly sclerotized band in position of gonobase (fig. 3F); long membranous midventral genital process present (figs. 3G, 3H), presumably fragmentum from base of penis; penis valves and gonostyli directed posteriorly (figs. 3F, 3H); gonostylus arising near outer distal margin of gonocoxite (figs. 3F, 3H), flattened, so that in lateral view it is rather broad and subapically constricted (fig. 3H), in dorsal view very slender apically.

Pale areas of head yellowish brown, upper median part of supraclypeal area black. Genal and hypostomal areas black. Flagellum black. Pronotum including pronotal lobe, mesoscutellum, and mesepisternum black. Legs yellowish brown, distal parts of femora, basal parts of tibiae, and distal parts of meso- and metatibia infuscated. Metasoma with T1 testaceous, with broad preapical dusky band; remaining terga cleared for study but apparently dusky testaceous (note that when dissected the metasoma appears pale testaceous).

Pubescence generally thinner and sparser than in female, particularly on clypeus, mesoscutellum, and mesepisternum; pubescence of head, mesosoma, and legs largely ochraceous. Mesoscutum almost without banding of setae; setae of mesepisternum and sides of propodeum white, somewhat less dense than in worker; dense setae of anterior part of mesepisternum dusky.

HOLOTYPE: ⚲, Thailand, Kanchanaburi [Province], Thong Pha Phum [District], 17.ix.2007 [17 September 2007], Y. Boontop, nest 2 ( SEMC). The holotype is from nest number 2 in Boontop’s records, a site 549 m above sea level at coordinates 14.42° N, 98.28° E.

PARATYPES (2♂♂, 340⚲⚲): 1♂, same data as holotype except nest 4 ( SEMC) ; 1♂, same data as holotype except 12.iii.2008 [12 March 2008] and nest 11 ( SEMC) ; 24⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 1 (16 SEMC, 2 CSCA, 2 DZUP, 2 EMBT, 2 ICNC) ; 11⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 1 ( SEMC) ; 18⚲⚲, same data as holotype (16 SEMC, 2 EMBT) ; 17⚲⚲, same data as holotype except 12. iii.2008 [12 March 2008] (9 SEMC, 4 AMNH, 2 BBSL, 2 CNIN) ; 24⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] (16 SEMC, 2 NHML, 2 SANC, 2 USNM, 2 EMBT) ; 8⚲⚲, same data as holotype except nest 3 ( SEMC) ; 13⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 3 ( SEMC) ; 14⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 3 (10 SEMC, 2 ZMHB, 2 ZISP) ; 2⚲⚲, same data as holotype except nest 4 ( SEMC) ; 12⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 4 (10 SEMC, 2 KSMA) ; 11⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 4 ( SEMC) ; 2⚲⚲, same data as holotype except nest 5 ( SEMC) ; 14⚲⚲, same data as holotype except 12. iii.2008 [12 March 2008] and nest 5 (11 SEMC, 3 EMBT) ; 15⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 5 (11 SEMC, 2 KUEC, 2 EMBT) ; 5⚲⚲, same data as holotype except 31.vii.2006 [31 July 2006] and nest 6 ( SEMC) ; 9⚲⚲, same data as holotype except nest 6 ( SEMC) ; 15⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 6 (13 SEMC, 1 FSCA, 1 LIPI) ; 21⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 6 (19 SEMC, 1 FSCA, 1 LIPI) ; 5⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 7 ( SEMC) ; 12⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 7 ( SEMC) ; 5⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 8 ( SEMC) ; 9⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 9 ( SEMC) ; 5⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 10 ( SEMC) ; 4⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 10 ( SEMC) ; 14⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 11 ( SEMC) ; 3⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 11 ( SEMC) ; 6⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 12 ( SEMC) ; 3⚲⚲, same data as holotype except 27.vii.2009 [27 July 2009] and nest 12 ( SEMC) ; 8⚲⚲, same data as holotype except 12.iii.2008 [12 March 2008] and nest 13 ( SEMC) ; 2⚲⚲, same data as holotype except 31.vii.2006 [31 July 2006] and nest 19 ( SEMC) ; 2⚲⚲, same data as holotype except 17.ix.2007 [17 September 2007] ( SEMC) .

ADDITIONAL MATERIAL: A further six workers are remarkably similar to T. malaipanae and we tentatively include them here, pending further work on these more southern populations, particularly utilizing morphometrics, males, and DNA data: 4⚲⚲, Thailand, Nakhonsithammarat , Khao Laung, 3.v.2007 [3 May 2007], Y. Boontop, nest 11 [a site 359 m above sea level at coordinates 8.49° N, 99.78° E] ( SEMC); 2⚲⚲, Thailand, Suratthani, Khao sok, 3.v.2007 [3 May 2007], Y. Boontop, nest 15 [a site 421 m above sea level at coordinates 8.91° N, 98.52° E] ( SEMC) .

COMMENTS: Probably variation in coloration of males is more or less comparable to that of workers. The male taken 12 March 2008 at nest number 11 differs from the male described above as follows: integument of head and mesosoma (including clypeus and tegula) black; scape and pedicel reddish brown; legs dusky pale brown; meso- and metatarsi and distal parts of tibiae blackish, palest areas on outer and posterior surfaces of protibia and basal parts of meso- and metatibiae; metasoma reddish brown with vague transverse dusky areas, apical terga darker; membranous midventral genital process not evident (likely a result of damage during dissection).

ETYMOLOGY: The specific epithet honors Savitree Malaipan of the Department of Agriculture, Kasetsart University, Bangkok, beloved mentor of Y.B. and a prominent Thai melittologist.

Figures

FIGURE 1. Worker of Tetragonula malaipanae, new species. A. Lateral habitus. B. Dorsal habitus. C. Facial view.

FIGURE 2. Male of Tetragonula malaipanae, new species (specimen with metasoma dissected). A. Lateral habitus. B. Dorsal habitus. C. Facial view.

FIGURE 3. Male of Tetragonula malaipanae, new species. A. Outer view of metatibia and metabasitarsis. B. Dorsal view of T7 (arrow indicates the position of the spiracle on the side of the sclerite). C. Ventral view of S5. D. Ventral view of S6. E. Ventral view of S7. F. Male genitalia (dorsal view at left, ventral view at right), distal part of membranous aedeagus omitted. G. Midventral membranous process. H. Male genitalia in right lateral view.