Polyrhachis varicolor Viehmeyer, 1916

Jaitrong, Weeyawat, Yamane, Seiki & Noon-Anant, Nawee, 2023, The Thai species of the Polyrhachis (Myrmatopa) flavicornis Smith, 1857 species group, with description of a new species (Hymenoptera, Formicidae Formicinae), Zootaxa 5249 (4), pp. 446-464 : 460-463

Polyrhachis varicolor Viehmeyer, 1916

( Figs 8–9 )

Polyrhachis (Campomyrma) fruhstorferi subsp. varicolor Viehmeyer, 1916: 163 , worker & queen, Singapore.

Polyrhachis varicolor: Kohout 2008: 259 (raised to species); Noon-anant et al. 2009: 177, figs 3–8; Khachonpisitsak et al, 2020: 75; Wang et al. 2022: 59.

Non-type material examined. THAILAND: W Thailand, Prachuab Khiri Khan Prov., Nakon Si Thamarat Prov. , 180 m alt., lower-vegetation, 8.III.2006, N. Noon-anant leg., NAW-POL6-024 (workers, PSUSC, SKYC) ; Central Thailand, Nakhon Nayok Prov., Muaeng Dist., near Nang Rong Temple , nest under leaf, 26.III.2021, W. Jaitrong leg., TH21-WJT-003 ( THNHM, workers, dealate queen, alate queens, males) ; S Thailand, Nakhon Si Thammarat Prov., Khao Nan NP, Yod Nam Waterfall , 27.IX.2008, Sk. Yamane leg. (worker, SKYC) .

Measurements and indices. Worker (10 non-types). TL 3.05–4.65, HL 1.30–1.45, HW 1.00–1.25, SL 1.75– 1.95, PW 0.85–1.05, MTL 1.50–1.75, CI 80–83, SI 150–180. Queen (3 non-types). TL 5.00–5.45, HL 1.60–1.70, HW 1.25, SL 1.90-2.05, PW1.45–1.50, MTL 1.85–2.00, CI 74–78, SI 152–164. Male (non-type). TL 4.8, HL 0.9, HW 0.65, SL 1.00, PW 1.25, MTL 1.7, CI 72, SI 154.

Description of worker ( Fig. 8 A-C)

Head in full-face view distinctly longer than broad, with posterior margin evenly and roundly convex, lateral margins distinctly converging anteriad. Frontal carinae in full-face view posteriorly reaching level of mid-length of eye, parallel anteriorly, divergent in middle, parallel posteriorly; frontal carina in profile distinctly elevated. Clypeus in dorsal view transverse, trapezoidal; its posteromedian margin straight to very shallowly emarginated; anterior margin slightly convex; anteromedian portion weakly produced with its anterior margin straight and usually with acute lateral angles. Mandible subtriangular, masticatory margin with five distinct teeth. Antennal scape long, ca. 1.30–1.37 times as long as head width including eyes; pedicel (antennal segment II) about 2 times as long as antennal segment III; all flagellomeres longer than broad with the first shortest. Eye in full-face view convex and prominent, distinctly breaking lateral margin of head, located posterior to mid-length on lateral face of head.

Pronotum in dorsal view much broader than long, anteriorly and laterally weakly convex, with very shallowly concave posterior margins; humerus bluntly angled or produced as small process; in profile view lateral face of pronotum with shallow furrow along its anterior margins; posteroventral corner broadly rounded. Mesonotum in dorsal view demarcated anteriorly and posteriorly by distinct furrows, broader than long, gradually narrowed posteriad, posteriorly much narrower than pronotum; in profile view dorsal margin almost flat but lateral keel with angle in its posterior half; mesopleuron anteriorly demarcated from pronotum by sinuated deep furrow but completely fused with metapleuron. Metanotal groove short (‘narrow’) and shallow, continuing down to metathoracic spiracle that has an upward-directed small opening. Propodeum in dorsal view as broad as mesonotum posteriorly; dorsal face rectangular, slightly broader than long, gradually merging with posterior declivity; propodeal spine short, upward directed; lateral face not demarcated from metapleuron; propodeal lobe very small; propodeal spiracle located on lateral margin of declivity, prominent, with oblong opening.

Petiole in dorsal view broader than long; dorsal face not clearly differentiated from anterior and posterior slopes, with pair of long lateral spines that diverge in basal part and are parallel in apical two-thirds, without denticle between them; in profile view anterior slope of node straight, much shorter than posterior slope that is roundly convex; subpetiolar process weakly developed, subtrapezoid with straight ventral margin.

Vertex and frons of head areolate-rugose, area between frontal carinae puncto-reticulate, areas between eyes and frontal carinae weaklier sculptured; gena behind eye and venter of head densely puncto-reticulate. Clypeus densely punctate. Mandible in basal half very densely and finely striate with scattered punctures from which setae arise; apical half with much sparser and weaker sculpture and shiny.Antenna densely micropunctate. Dorsum of pronotum puncto-striate, but with weak striation; mesonotum and dorsum of propodeum densely macropunctate; lateral face of mesosoma including lateral face of pronotum densely macropunctate. Petiole densely macropunctate. Gastral tergites finely micropunctate and matte; sternites with coarser punctures but interspaces shiny. Legs micropunctate and matte.

Dorsa of head, mesosoma, petiole, and gaster almost without standing hairs; few very short standing hairs present on outer margin of mandible, clypeus anteriorly, frontal lobe, petiolar sternite anteriorly and venter of gaster. Eye without standing hairs. Antennal scape without standing hairs. Body brown to dark reddish brown; gaster darker than elsewhere [in some specimens gaster with similar color or slightly paler than head and mesosoma]

Description of queen ( Fig. 9 A–C )

General habitus similar to the worker except for caste-specific structures. Body slightly larger than the average worker with head width 1.25 mm (1.00– 1.25 mm in worker). Eye larger and more prominent; ocelli arranged in low triangle. Anterolateral corner of pronotal dorsum round, without any projection. Mesoscutum without notauli, with weak parapsidal line in posterior half of scutum; prescutal carina absent; mesopleuron divided into upper and lower sections by groove; anterior margin of lower section with high acute keel (not conspicuous in the worker). Metanotum in dorsal view short (‘narrow’), indented, sharply demarcated from propodeum by deep furrow; metapleuron barely differentiated from mesopleuron, completely fused with propodeal side; propodeal spines short, blunt. Body slightly hairier; in addition to standing hairs mentioned for the worker, queen bears standing hairs as follows: one or two around ocelli, several on mesoscutum, some on mesoscutellum, some on second to fifth gastral tergites. Body color almost identical to the worker.

Description of male ( Fig. 9 D–F )

Head in full-face view longer than broad, but if including eyes, then distinctly broader than long. Clypeus in dorsal view broad, with transverse impression in its median portion, posteriorly clearly demarcated from frons, with posteromedian margin shallowly emarginated medially and anterior margin broadly convex. Mandible spatulate, weakly sclerotized, twice as long as broad with outer margin curved and apex bluntly pointed; masticatory margin short and edentate. Eye large, positioned at mid-length of lateral face of head; distance between mandibular base and anterior margin of eye (malar space) half as long as major diameter of eye. Antennal scape moderately long, as long as head width including eyes.

Mesosoma in dorsal view much broader than head including eyes. Pronotum in dorsal view short (‘narrow’), almost entirely concealed by inflated mesoscutum. Mesoscutum with faint median line, without notauli; parapsidal line present in posterior half of scutum; scuto-scutellar sulcus prominent; mesoscutellum much narrower than mesoscutum, distinctly narrowed posteriad. Metanotum short (‘narrow’), indented, clearly defined from propodeum with deep furrow. Propodeum without separation of dorsum from declivity; spines absent. Petiole low and globular, in dorsal view as broad as long. Gaster rather weakly sclerotized, easily deformed after drying.

Entire body superficially and finely sculptured, weakly shiny. Short appressed hairs present over body surface; standing hairs confined to following parts: clypeus with two to three long hairs anteriorly; mandible with some long hairs of varying length on outer surface; standing hairs on maxillary and labial palpi numerous; mesoscutum without standing hairs; mesoscutellum without standing hairs but with sparse appressed hairs that are relatively short; a few standing hairs present in posterolateral area of propodeum and around propodeal spiracle; petiole with ca. 20 fine standing hairs dorsally, pair of standing hairs present on sternite posteriorly, and thick golden hairs anteriorly; gastral tergites generally lacking standing hairs except on apical tergites; gastral sternite with more standing hairs; coxae of all legs with sparse standing hairs. Eye without hairs that are recognized under high magnifications (>100 x). Body brown to dark brown; mandible, legs and genitalia yellowish or light brown; maxillary and labial palpi yellowish. The male of P. varicolor is very similar to that of P. flavicornis but is distinctly larger than the latter (HW 1.25 mm in this species; 0.95–1.00 mm in P. flavicornis ).

Habitat. Nests of P. varicolor were found on the underside of plant leaves or between leaves in dry evergreen forests and evergreen forests (2–5 m above the ground). Silk, carton and other materials were used in constructing the nests.

Distribution. Thailand and Singapore ( Fig. 10 B ).

Remarks. Polyrhachis varicolor is similar to P. flavicornis . See under ‘Remarks’ of P. flavicornis .

Figures

FIGURE 8. Polyrhachis varicolor (non-type worker, TH21-WJT-003/1). A, Body in profile view; B, head in full-face view; C, body in dorsal view.

FIGURE 9. Polyrhachis varicolor.A–C, Non-type dealate queen (TH21-WJT-003/2); D–F, non-type male (TH21-WJT-003/3); A, D, body in profile view; B, E, body in dorsal view; C, F, head in full-face view.

FIGURE 10. Distribution map of Polyrhachis flavicornis species group. A) P. constructor and P. longipilosa sp. nov. B) P. flavicornis and P. varicolor.