Rhopalomastix murphyi, Wang & Yong & Jaitrong, 2018

Wang, Wendy Y., Yong, Gordon W. J. & Jaitrong, Weeyawat, 2018, The ant genus Rhopalomastix (Hymenoptera: Formicidae: Myrmicinae) in Southeast Asia, with descriptions of four new species from Singapore based on morphology and DNA barcoding, Zootaxa 4532 (3), pp. 301-340 : 323-327

Rhopalomastix murphyi sp. n.

( Figs. 40–51 )

Type. Holotype. Worker. SINGAPORE, Upper Thomson Nature Park (1.38653°N, 103.81938°E), in bark of Durio zibethinus L. tree, 24 Oct 2016, G.W. Yong & S.X. Chui leg., ZRC _ENT_00000874 ( ZRC).

Paratypes. Fifty-five workers ( MCZ, THNHM, USNM, ZRC), 3 dealate queens ( ZRC), 6 males ( THNHM, ZRC), same data as holotype, colony no. GY-SG16-RhoA, ZRC _HYM_0000287 .

Diagnosis. Worker. Workers monomorphic with little size variation; small size (HL 0.40–0.44, HW 0.36– 0.41). In profile view, clypeus evenly and broadly convex, projected forward slightly from dorsal margin of head; posterior half of head smooth and shiny; ventral surface of head and outer surface of femora largely smooth and shiny; upper part of mesopleuron rugulose-reticulate, interspaces punctured and dull; anterior face of petiole weakly concave, smooth and shiny without hairs. Body colour generally uniform yellowish-brown, head and mesosoma slightly darker in tone.

Queen. Small size (HL 0.42–0.45, HW 0.38–0.42), head slightly more rectangular than that of worker. In profile view, clypeus broadly and evenly convex; posterior half and ventral surface of head, outer surface of femora, dorsum of mesosoma and gaster largely smooth and shiny; pronotum in dorsal view short, anterior pronotal margin roundly convex; anterior face of petiole weakly concave and steep, smooth and shiny without hairs. Body colour generally uniform light brown, head, dorsum of mesosoma and gaster slightly darker in tone.

Male. Small size (HL 0.4–0.42, HW 0.37–0.4). Head in profile view subtrapezoidal, ventral margin below eye almost entirely straight; ocelli large; clypeus in profile short and rounded, punctate but shiny; petiole very short and wedge-shaped, apex smooth and blunt; dorsal outline of postpetiole flat, much longer than ventral margin; cinctus between postpetiole and gaster very weak. Entire body mostly smooth and shiny; petiole and postpetiole with sparse standing hairs. Body colour generally grey-brown; head, dorsum of mesosoma and distal half of gaster darker in tone.

Worker measurements. Holotype: TL 1.69; HL 0.43; HW 0.39; SL 0.15; ML 0.48; PronW 0.26; EL 0.08; EW 0.04; CI 91; REL 21; SI 38.

Two paratypes and eight non-types (n = 10): TL 1.59–2.07; HL 0.40–0.44; HW 0.36–0.41; SL 0.15–0.18; ML 0.44–0.50; PronW 0.26–0.29; EL 0.07–0.08; EW 0.04–0.05; CI 90–95; REL 18–21; SI 40–47.

Queen measurements. Three paratypes and three non-types (n = 6): TL 1.94–2.46; HL 0.42–0.45; HW 0.38- 0.42; SL 0.18–0.19; ML 0.62–0.70; MsW 0.32–0.42; EL 0.15–0.16; EW 0.09–0.10; CI 89–93; REL 36–40; SI 43– 47.

Male measurements. Six paratypes (n = 6, except for HW, CI, REL, SI (n=2)): TL 2.11–2.31; HL 0.40–0.42; HW 0.37–0.4; SL 0.07–0.10; ML 0.70–0.74; MsW 0.32–0.42; EL 0.18–0.22; EW 0.16–0.18; CI 93–95; REL 54– 55; SI 19–25.

Description. Worker. Small sized, with little size variation. Head in full-face view subrectangular, slightly longer than broad, lateral margins weakly convex or almost parallel to each other, posterior margin broadly convex with a weak median depression. Eye relatively small, with 10–13 ommatidia. In profile view, clypeus evenly and broadly convex, projected forward slightly from dorsal margin of head. Antennal scape short and almost uniformly thin, reaching midlength of lead when laid backwards. Mesosoma in profile subcylindrical and elongate, slightly longer than head length, anterior rising margin of pronotum truncate compared to posterior declining face of propodeum, dorsal outline almost straight; dorsolateral corner of propodeum rounded and smooth, propodeal declivity shallowly concave. In dorsal view, mesosoma subrectangular, anterior pronotal margin strongly convex and rounded, posterior propodeal margin weakly concave. In profile, petiole inclined posteriorly, slightly longer than high, anterior margin steep and weakly concave, anterior face distinct from apical face, petiolar node subtrapezoidal, apex smooth and blunt, directed postero-diagonally. Petiole higher and longer than postpetiole, postpetiole in profile view quadrant in shape, dorsal margin broadly convex. In dorsal view, petiole elliptical in shape, nearly twice as broad as long; postpetiole globular, wider than long, slightly wider and longer than petiole.

Posterior half of head including dorsum, lateral surfaces and venter mostly smooth and shiny, anterior half of head including antennal scrobe and area surrounding eye with feeble striations, partly superficially reticulate. Median clypeal surface with sparse punctures. Mandible mostly smooth and shining with punctures concentrated to small area close to masticatory margin. Lateral surface of mesosoma mostly weakly striate-reticulate and shiny, upper part of mesopleuron, i.e. anepisternum, rugulose-reticulate, interspaces punctured and dull; dorsal surface of mesosoma striated and shining, except for smooth and shining spot antero-median of pronotal dorsum. Lateral and dorsal surfaces of petiole, postpetiole weakly punctate, largely smooth and shining. Gaster mostly smooth and shining, with scattered punctures.

Dorsal surface of head with abundant short erect hairs and sparse long erect hairs; no standing hairs on central median shiny strip, and antennal scrobe; no hairs on gena, ventral surface with short appressed hairs, antenna with many short standing hairs. Sparse pilosity on mesosoma dorsum, scattered short erect hairs and sparse longer hairs concentrated close to dorsolateral sides. Petiolar node with short erect hairs of generally uniform length, and 1–2 pairs of much longer erect hairs; dorsal surface of postpetiole also with multiple short erect hairs of uniform length and a pair of much longer erect hairs. Gaster pilose, surfaces covered with abundant short standing hairs, sparse long standing hairs.

Overall generally uniformly yellowish-brown, head and mesosoma slightly darker in tone, legs and antennae brownish yellow and lighter in tone, tips of antennae pale yellow.

Queen. Relatively small size. Head in full face view subrectangular, slightly more rectangular than that of worker; lateral margins weakly and broadly convex, almost parallel to each other; posterolateral corners smooth and rounded, posterior margin nearly straight with a weak median depression. Posterior margin of eye located approximately at transverse midline of head in full face view. In profile, clypeus broadly and evenly convex. Antennal scape short, exceeding transverse midline of head by less than a quarter its length when lain back. In profile, mesosoma sub-cylindrical, more elongate than that of worker, dorsal outline broadly and weakly convex, posterior propodeal declivity steep and almost vertical; oblique mesopleural sulcus distinct but not deeply impressed, metapleural outline indistinct. In dorsal view, mesosoma sub-cylindrical, anterior margin of pronotum roundly convex, humeral corners rounded and smooth, pronotum relatively short, mesoscutum almost as wide as long. In profile view, petiole slightly inclined posteriorly, anterior rising margin steep and weakly concave; petiolar apex rounded and smooth, posterior declivity steep and weakly convex, about half the length of anterior margin. In dorsal view, petiole sub-oblong, about twice as wide as long; postpetiole globular, larger than petiole, wider than long.

Posterior half of head, including dorsum and venter, and ventral head surface mostly smooth and shining; anterior half of head striate-reticulate and shiny; interspaces surrounding eye punctured but shining. Median section of clypeus largely smooth and shining. Mandible mostly smooth and shining with very feeble striations, area close to masticatory margin with sparse punctures. Lateral surface of mesosoma weakly striate-reticulate, interspaces smooth and shining; dorsal surface mostly smooth and shining, with superficial striate-reticulate sculpture. Lateral and dorsal surfaces of petiole and postpetiole superficially reticulate, interspaces smooth and shining; anterior rising face of petiole smooth and shining. Gaster largely smooth and shining.

Dorsum of head with short standing hairs of nearly uniform length, arranged approximately along two rows on frons, sometimes with up to 2 longer erect hairs; antennal scape with scattered uniformly short standing hairs, interspersed by sparse longer erect hairs; hairs on gena short and sparse, appressed or standing. Ventral surface of head with scattered short appressed hairs. Dorsum of mesosoma with sparse pilosity, sparse short standing hairs mainly on anterior half of mesoscutum; longer erect hairs scattered along dorsolateral margin, mainly on anterodorsal margin of pronotum. Rising face of petiole without hairs, apex with sparse short standing hairs, and two pairs of longer erect hairs. Dorsal surface of postpetiole with many short suberect hairs and at least a pair of longer erect hairs. Gaster pilose, dorsal surfaces mainly with abundant suberect and decumbent short hairs, ventral surfaces with abundant appressed and subdecumbent short hairs, both surfaces with sparse longer standing hairs. Pilosity denser close to distal end of gaster, around pygidium.

Entire body generally uniform light-brown; head, dorsum of mesosoma and gaster slightly darker in tone.

Male. Small size. Head in full face view broad-ovate, posterior margin strongly convex; ocelli large relative to head width; eye very large, extending past midline of head and close to posterior head margin at its maximum diameter, outline of eye strongly convex and exceeding lateral margin of head. In profile, head subtrapezoidal, ventral margin below eye almost entirely straight, lateral corners smooth and rounded; clypeus short and rounded, strongly projected from dorsal margin of head. In profile, mesosoma sub-cylindrical and relatively elongate, dorsal outline broadly and weakly convex, posterior face of propodeum short and weakly convex. In dorsal view, mesosoma slightly obovate, notauli absent. In profile view, petiole inclined posteriorly, longer than high, anterior margin gently concave and longer than posterior margin, very short and wedge-shaped, apex smooth and blunt, posterior face gently sloping and broadly convex; anteroventral extension of subpetiolar process reduced to a translucent shallow and narrow lamella. Dorsal outline of postpetiole flat, much longer than ventral margin, forming an almost continuous outline with dorsum of gaster, only differentiated from the latter by a very weak cinctus.

Surfaces of head mostly smooth and shining, anterior half of dorsum and ventral surface of head weakly striate-punctate, clypeus punctate but shiny. Lateral surface of mesosoma superficially reticulate, interspaces smooth and shining, dorsum mostly smooth and shining, with feeble superficial striate-reticulate sculpture. Lateral and dorsal surfaces of petiole and postpetiole, and gaster superficially reticulate, largely smooth and shining.

Dorsal and ventral surfaces of head with abundant short erect and sub-decumbent hairs, posterior surface of head also with abundant subdecumbent and appressed hairs. mesoscutum with well-spaced subdecumbent and suberect hairs; ventral surface of episternum, coxa and legs with abundant short, erect, subdecumbent and appressed hairs. Petiole, postpetiole with sparse short standing hairs of uniform length. Gaster very pilose, both dorsal and ventral surfaces covered with abundant standing and subdecumbent hairs of moderate length.

Entire body generally uniform grey-brown; head, dorsum of mesosoma, and posterior half of gaster slightly darker brown in colour.

Distribution. Singapore.

Etymology. The specific name is dedicated to D.H. Murphy, who first collected Rhopalomastix in 1981; these specimens were deposited in ZRC and later identified as this species.

Habitat. The type series was derived from a rather large colony with numerous workers and multiple dealate queens, occupying an extensive area of bark on a durian tree ( Durio zibethinus ) in an abandoned plantation forest.

Remarks. Rhopalomastix murphyi sp. n. is most similar to R. glabricephala . See ‘Remarks’ under R. glabricephala .

Non-type material examined. SINGAPORE: 3 workers, locality unknown, secondary forest, 14 Apr 1993, Sk. Yamane leg., ZRC _HYM_0000584, 585 (ZRC); 12 workers, Mandai Lake Road (1.40915°N, 103.78234°E), durian tree, 0 3 Nov 2016, G. W. Yong & C. Peeters leg., ZRC _HYM_0000507 (THNHM; ZRC); 16 workers, 10 males, Upper Thomson Nature Park , 2 Nov 2016, G. W. Yong & C. Peeters leg., colony no. SP 021116 -1 ( THNHM); Bukit Timah forest, 2 Jan 1981, D.H. Murphy leg., colony no. DHM-SG81- Rho 1, ZRC _HYM_00 0 0 0 0 9 (ZRC).

DNA barcoding. Four individuals from the same colony as the type series (ZRC_HYM_0000287), and eight others from another colony (ZRC_HYM_0000507) collected from a different locality—Mandai Lake Road—were successfully barcoded. These barcodes clustered into two near-identical (0.3% divergence) haplotypes, 19.2% differentiated from all other species of Rhopalomastix ( Fig. 1 )

Figures

FIGURE 1. Cluster dendrogram of COI (313 bp) barcodes of Rhopalomastix from Singapore and Thailand. Objective clustering of barcodes was performed based on uncorrected p-distances using the ‘best close match’ criteria; the number at each ‘node’ represents the percentage divergence or pairwise distance threshold at which clusters split or lump together. Each cluster identified as a species is highlighted in one colour per respective species. Sequences of Thai Rhopalomastix are outlined in red.

FIGURES 40–43. Paratype worker of R. murphyi sp. nov. 40, habitus in profile; 41, head in full-face view; 42, closeup of head in profile view; 43, body in dorsal view.

FIGURES 44–47. Paratype queen of R. murphyi. 44, habitus in profile; 45, head in full-face view; 46, body in dorsal view; 47, closeup of mesosoma in dorsal view.

FIGURES 48–51. Paratype male of R. murphyi. 48, habitus in profile; 49, head in full-face view; 50, body in dorsal view; 51, closeup of mesosoma in dorsal view.