Polyrhachis (Myrma) cyaniventris

Sorger, D. M. & Zettel, H., 2009, Polyrhachis (Myrma) cyaniventris F. Smith, 1858 (Hymenoptera: Formicidae) and a related new ant species from the Philippines., Zootaxa 2174, pp. 27-37 : 29-30

The Polyrhachis (Myrma) cyaniventris species group

(Figs 1-12)

Diagnosis of worker: Large (TL 7.9-11.5 mm), stout, finely sculptured, matte ants with peculiar metallic, in most species bluish, shimmer. Setae short, black, and in low numbers on body, scape, and legs, or totally absent. Eyes not surpassing outlines of head in full face view (Figs 1, 7). Ventrolateral margin of head rectangular or obtuse (Figs 1, 7). Antennae and legs rather short (compared with species of the P. relucens group), scape strongly widened towards apex, there about twice as wide as at base, SI 132-155. Dorsolateral margin of mesosoma sharp and protruded, strongly indented between nota (Figs 2-4, 8-10). Pronotal spines prominent (Figs 1, 2, 4, 7, 8, 10). Propodeum without spines, with distinct transverse carina (Figs 3, 9) separating slightly convex dorsal from concave caudal face which is higher than petiole (Figs 2, 8). Petiole wide, with two pairs of spines dorsolaterally; ventral pair short, dorsal pair very long, curved and embracing base of gaster (Figs 2, 4, 8, 10). Anterior face of gaster concave (Figs 2, 8).

Diagnosis of gyne (gyne of P. pirata sp.n. unknown): Similar to worker, except the following: TL 9.4-10.9 mm. Eyes slightly surpassing head sides (Fig 5). Dorsolateral margin of mesosoma incomplete, but present on anterior three-fourths of pronotum and on propodeum (Fig 6). Spines of petiole shorter than in worker and hardly curved.

Males: No males were available for this study, but males of P. cyaniventris were reported to be held in the Museum of Comparative Zoology, Cambridge, U.S.A. (G. Alpert, in litt.)

Description of worker: Body with metallic shimmer, petiole and gaster dark bluish. Mandibles black. Palpi brown. Antennae in most species black, except tip of apical segment reddish brown. Legs, except femora, usually black.

Body, legs and antennae with isodiametric reticulum or very fine and dense puncturation, locally overlaid with longitudinal rugae; with fine, short, appressed golden or silverish white pubescence.

Head stout, longer than wide, broadest at level of antennal fossae, sides and venter forming right to obtuse angle; dorsum and sides with appressed pubescence; sides of head convex. Venter of head almost smooth, with very sparse pubescence. Eyes very small, in frontal view located in upper third of head and laterally not breaking its outline in full face view (Figs 1, 7). Ocelli usually absent or very indistinct. Occipital margin with medial lobe (Figs 1, 7). Frontal carinae high (Figs 1, 7). Clypeus in profile slightly sinuate, proximally convex, distally concave (Figs 2, 8); with obtuse elevation along midline; anterior margin with row of long golden setae (1, 7). Mandibles with longitudinal striation, fine at base, coarser towards masticatory margin; numerous pits with long, golden setae distally.

Mesosoma dorsolaterally with strongly developed, sharp margin deeply indented between segments (Figs 2, 4, 8, 10). Dorsal face in side view convex (Figs 2, 8), with fine, short, appressed pubescence. Pronotal spines long, directed anterolaterad (Figs 1, 2, 4, 7, 8, 10). Propodeum with transverse ridge separating dorsal and posterior face and laterally forming short, blunt teeth (Figs 2-4, 8-10).

Petiole stout, biconvex in lateral view (Figs 2, 8), armed with two pairs of spines dorsolaterally; the slightly more ventral pair short, but acute, the dorsal pair very long, curved and embracing base of gaster (Figs 2, 4, 8, 10). Gaster with anterior face slightly concave, tergites with varying number of short, black setae (Figs 2, 8).

Species included: Polyrhachis cyaniventris, P. pirata sp. n.

Distribution: Only known from the Philippines (Figs 11, 12).

Discussion: Taxonomic knowledge on the species-rich subgenus Myrma is summarized by Dorow (1995). Since Forel (1915) numerous authors have given priority to the name Polyrhachis over Myrma , and finally they were followed by Opinion 1919 of the International Commission of Zoological Nomenclature (ICZN 1999). Polyrhachis cyaniventris was placed in the P. militaris-relucens group by Emery (1925); it contains African and Australasian species and is defined by long pronotal spines, flat or concave dorsum of mesosoma, and petiole with four spines or, rarely, dorsally convex and without spines. Polyrhachis cyaniventris does not properly fit into any Ethiopian species group established by Bolton (1973). Kohout (1989) defined the P. relucens group as a part of Emery's (1925) P. militaris-relucens group which is widely distributed and species-rich in Australasia and has several representatives in the Philippines. Kohout (2008) presents a key to the subgenera and species groups of Polyrhachis occurring on Sulawesi, recognizing five species groups in Myrma from this island. Although P. cyaniventris fits the character set of Kohout's (1989, 2008) P. relucens group, there are several differences from typical species of this clade (in the sense of Kohout 1989), e.g., P relucens (Latreille 1802) and P. illaudata (Walker 1859), which in our opinion justifies the separation of P. cyaniventris and related species and the establishment of a separate group. The main distinguishing characteristics of the P. cyaniventris group, if compared with Kohout's (1989) P. relucens group, are the metallic shimmer of the integument, a strong reduction in pilosity, small and less protruding eyes (most peculiar in workers), short legs, a high propodeum, and long dorsal spines of the petiole, that are curved posterolaterad and embrace the gaster's base in the worker caste.

Key to species (workers)

1 Propodeum relatively broader, PPI 152-189. Small species (TL 7.9-9.0-10.1 mm; HW 1.70-2.30 mm) with numerous setae on entire body: vertex with 2-13-20, mesosoma dorsally with 3-36-60, tergite 1 of gaster with 4-25-40 short black setae. Pronotal spines in cross-section flat. Sculpture of integument coarse; microsculpture of head, mesosoma and gaster overlaid with longitudinal striation. Ridge separating dorsal and posterior face of propodeum sinuate, medially not depressed. Head and mesosoma with dark bluish shimmer.................................. P. cyaniventris

- Propodeum relatively narrower, PPI 114-137. Large species (TL 10.1-10.8-11.5 mm; HW 2.19-2.50 mm) with only few short black setae on entire body: vertex, dorsum of mesosoma and tergite 1 of gaster without setae (rarely with 2 setae on vertex). Pronotal spines in cross-section triangular and massive. Sculpture of integument fine; microsculpture of propodeum overlaid with fine longitudinal striation. Ridge separating dorsal and posterior face of propodeum sinuate, medially slightly depressed. Head and mesosoma with greenish to coppery shimmer.................. ................................................................................................................................................................P pirata sp. n.