Perissomyrmex medogensis

A nest containing about 70 individuals was found inside decayed wood in a ground sample, only one queen was included in the nest. Among the 31 individuals collected, one queen (3.2%), two soldiers (6.5%), and 28 workers (90.3%) were involved. The collection data shows that the species is monogynous and nests inside decayed wood, workers are weakly dimorphic and possibly forage on the ground, and the soldier caste only occupies a small percentage. (Xu and Zhang 2012)

Identification
Xu and Zhang (2012) - This new species is close to Perissomyrmex bidentatus but head and body smooth and shiny; propodeal spines short, about 1/3 length of propodeal dorsum; color black.

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Nomenclature

 *  medogensis. Perissomyrmex medogensis Xu & Zhang, 2012: 149, figs. 6-21 (s.w.q.) CHINA.

Worker
Holotype. TL 4.0, HL 1.00, HW 1.00, CI 100, SL 0.88, SI 88, ED 0.16, PW 0.58, AL 1.10.

In full face view, head nearly square, as broad as long. Occipital margin weakly convex, occipital corners rounded. Lateral sides evenly convex, widened forward. Mandibles rectangular, inner margin with one tooth, masticatory margin with three teeth; with diastema between subapical and basal tooth. Backward extended median portion of clypeus triangular, posterior corner acutely angled, and followed by short longitudinal furrow. Anterior margin of clypeus with one pair of large triangular median teeth, apices curved outward, with deep notch between teeth. Antennae nine-segmented, scape surpassing occipital corners by about 2/7 of its length, antennal clubs three-segmented. Eyes circular and convex, located slightly before midpoints of lateral sides of head.

In profile view, promesonotum roundly convex, lateral sides of pronotum weakly marginate. Promesonotal suture distinct but not depressed, consisting of row of large punctures on the dorsum. Metanotal groove deeply depressed. Mesopleuron with oblique furrow. Dorsum of propodeum straight, weakly sloped down backward. Propodeal spines short and stout, apices slightly curved down, about 1/3 length of propodeal dorsum. Declivity weakly concave, about half length of propodeal dorsum. Propodeal lobes very short, rounded apically. Propodeal spiracle circular, high up on the lateral side, ventral and posterior sides of spiracle depressed. Petiolar node roughly triangular, anterodorsal corner prominent, posterodorsal corner weakly convex, anterior peduncle about as long as node. Ventral face of petiole weakly concave, anteroventral corner weakly convex. Postpetiolar node inclined backward, dorsum roundly convex, posterior face nearly vertical, posterodorsal corner prominent; ventral face of postpetiole nearly straight, anteroventral corner toothed.

In dorsal view, lateral sides of pronotum roundly prominent. Propodeal spines slightly curved inward. Petiole rectangular, petiolar node about as broad as long. Postpetiole widened backward, broader than petiole, postpetiolar node broader than long.

Mandibles sparsely coarsely longitudinally striate and with sparse large punctures. Head smooth and shiny, lateral areas between genae and antennal sockets sparsely coarsely longitudinally striate. Mesosoma smooth and shiny, metanotal groove with short costulae. Petiole and postpetiole smooth and shiny, posterior peduncles with short fine longitudinal striations. Gaster smooth and shiny, anterior margin with short basal costulae. Head and body with abundant erect to suberect hairs, almost without pubescence except for cervicum. Scapes with abundant subdecumbent hairs and abundant decumbent pubescence. Tibiae with abundant subdecumbent to decumbent hairs, but without pubescence. Color black. Mandibles, antennae, and legs brown.

Paratype. TL 3.9-4.1, HL 0.93-1.05, HW 0.95-1.05, CI 98-103, SL 0.85-0.93, SI 83-92, ED 0.15-0.16, PW 0.55-0.60, AL 1.08-1.18 (ten individuals measured). As holotype worker, but in some individuals, apices of median anterior clypeal teeth truncated or weakly bifid.

Paratype soldiers. TL 4.4-4.8, HL 1.28-1.45, HW 1.33-1.50, CI 103-104, SL 0.95-1.00, SI 67-72, ED 0.18, PW 0.65-0.73, AL 1.25-1.30 (two individuals measured). Similar to holotype worker, but body relatively larger, head proportionally larger and broader. In full face view, occipital margin weakly concave in the middle. Teeth on masticatory margins of mandibles very blunt or the whole margin edentate. Median teeth of anterior clypeal margin truncated, or teeth very short and closely approximated, with very shallow notch between them. Antennae relatively short, apices of scapes just reaching to occipital corners. In profile view, promesonotum relatively flat, promesonotal suture weakly depressed. Lateral sides of mesonotum with pair of prominences. Frons of head sparsely longitudinally striate. Mandibles, antennae, and legs blackish brown.

Morphological variations. The morphology of mandibles and clypeus of the species shows rich variations in worker, soldier, and queen castes. In the worker caste, the median teeth of anterior clypeal margin may exhibit as normal outward curved (67.9% individuals), apically truncated (17.9% individuals), and weakly apically bifid (14.3% individuals). In the two soldiers obtained, median teeth of anterior clypeal margin exhibit as apically truncated, and closely approximated shorter teeth. In the queen caste, the median teeth exhibit as apically truncated. Teeth on masticatory margins of mandibles show a normal state in the worker and queen castes, but the teeth are strongly reduced or even edentate in the soldier caste.

Queen
TL 5.0, HL 1.10, HW 1.18, CI 107, SL 0.90, SI 77, ED 0.16, PW 0.78, AL 1.35 (one individual measured). Similar to holotype worker, but body relatively larger. In full face view, occipital margin nearly straight. Median teeth of anterior clypeal margin truncated, as in the soldier. Antennae relatively shorter, scape surpassing occipital corners by about 1/7 of its length. Vertex with three ocelli. Mesosoma winged, but dealate. In profile view, mesonotum roundly convex and sloped down backward, massive in volume. Mesopleuron with oblique furrow. Metanotum very short, about 1/3 length of propodeal dorsum. Propodeal dorsum straight and sloped down backward, propodeal spines about half length of dorsum. In dorsal view, scutum of mesonotum with pair of parallel longitudinal furrows, posterior margin rounded. Anterior margin of scutellum bluntly angled, posterior margin rounded. Propodeal spines straight. Frons of head sparsely longitudinally striate, as in soldier.

Type Material
Holotype worker: China, Tibet, Medog County, Damu Town, 70K, N 29° 42.224', E 95° 31.346', 2750 m, collected from a nest inside decayed wood in a ground sample in Abies forest, on the south slope of Himalaya Mountain, 22.VII.2011, Cheng-Lin Zhang leg., No. A11-4178. Paratypes: 27 workers, two soldiers, and one queen, with the same data and collected from the same nest with the holotype worker.

Etymology
The new species is named after the type locality, Medog County.

References based on Global Ant Biodiversity Informatics

 * Liu X. 2012. Taxonomy, diversity and spatial distribution characters of the ant family Formicidae (Insecta: Hymenoptera) in southeastern Tibet. PhD Thesis 139 pages
 * Xu Z.H., and C.L. Zhang. 2012. Review of the myrmicine ant genus Perissomyrmex M.R. Smith, 1947 (Hymenoptera: Formicidae) with description of a new species from Tibet, China. Myrmecological News 17: 147-154.