Poneracantha lineolata

A specialized millipede feeder endemic to Hispaniola.

Identification
A member of the rastrata complex (in the rastrata subgroup of the rastrata species group). Head in frontal view subquadrate, scapes smooth and shining; mandibles denticulate; sculpturing of body striate, lacking propodeal denticle. (Lattke 1995)

This interesting species from central Hispaniola differs from the five previously described (endemic) Gnamptogenys from the island, two of them fossil in amber, by its combination of triangular mandibles, fairly large eyes, size, form of petiole, and fine, regular, costulate sculpture. G. lineolata seems to be a rather primitive species among both the Hispaniolan and the overall New World congeners. In Lattke (1993), G. lineolata would apparently fall into his rastrata group, and in his key it runs to couplet 54, where it agrees with rastrata in that the scape surpasses the vertexal margin by its apical width, but differs from rastrata in its larger size, finer sculpture, dentate mandibles, and quadrate head shape, among other things.

Key to New World Gnamptogenys Species

Distribution based on Regional Taxon Lists
Neotropical Region: Dominican Republic, Lesser Antilles.

Nomenclature

 *  lineolata. Gnamptogenys lineolata Brown, 1993: 275, figs. 1, 2 (w.) DOMINICAN REPUBLIC.

Description
Diagnosis, worker: A medium-small species (head width about 1.2, WL near 1.6 mm) with sides of head subparallel and feebly convex; eyes gently convex, EL almost one-fifth HL, situated distinctly behind mid-HL; vertexal margin weakly concave. Mandibles triangular, basal margin oblique, meeting the apical margin at an obtuse angle with a tooth, one of a short series of spaced, uneven, low teeth on the apical margin; blades striate to near apex. Apron of free clypeal margin straight, with rounded lateral corners; a narrow triangular space is left between the margin and the basal mandibular margins at full closure. Antennal scapes surpassing vertexal margin by about their apical thickness in fullface view; scapes smooth and shining, with spaced punctulae. Promesonotal suture arcuate, impressed, but not breaking the integumental surface; metanotal groove broad, impressed, so that the side-view dorsal outline of the alitrunk is gently convex at the promesonotum, and slightly lower and more feebly convex over the propodeal dorsum; declivity of propodeum rounding into dorsum, with a low, obtuse suggestion of a propodeal tooth barely perceptible on each side above mid-height; propodeal spiracle slightly raised, its round opening directed caudolaterad, placed very near the declivity near mid-height. Petiole thick but raised, node back-tilted, apex strongly rounded and highest caudad, broader than long; subpetiolar process triangular, with acute apex directed forward. Prora trailing a prominent carina caudad; constriction between A3 and A4 distinct, but moderate; T4 arched, so that $4 is moderately reduced, and the apical segments of the gaster are directed ventrad and slightly anteriad. Sculpture moderately shining, consisting mostly of very fine, regular, longitudinal striation over dorsal surfaces of head, alitrunk and gaster, arched over petiolar node, about 30-33 costulae between frontal carinae. Color brownish black to yellowish brown, the lighter examples often infuscate dorsad; appendages brown to yellowish.

Holotype worker: TL 5.6, HL 1.20, HW 1.14 (CI 94), ML 0.52 (MI 43), SL 1.00 (SI 88), EL 0.22, WL 1.70, metafemur L 1.20, metatibia L 1.00 mm. Worker paratypes (n=9): TL 5.2-5.8, HL 1.19-1.30, HW 1.11-1.19 (CI 90-96) mm.

Although the sides of the head are approximately parallel in full-face view, the anterior part is actually very slightly wider at about halfway between the eye and the anterior corner of the head; vertexal outline, while weakly concave mesad, is filled in by the convex outline of the nuchal rim behind it. The frontal lobes are moderately expanded, but do not cover all of the antennal insertions. The comb of stiff hairs in the basitarsal concavity opposing the strigil of the fore leg lacks a longer, specialized, stiff seta present in some other Gnamptogenys species.
 * Worker, further description:

Queen, male and lava unknown.

Type locality: REPUBLICA DOMINICANA, Prov. La Vega: (Parque Nacional) La Cienaga, 1100 m., broad-leaf valley forest with some pine, 7 workers: 2 workers under large stone in soil, plus 5 workers taken from berlesates of leaf litter at the same general locality of 4 February 1975 and 17 July 1986 (sort made 19 July), leg. W. L. Brown. Prov. La Vega, E1 Rio to Bonao, Km 22 (in or near Casabito Forest), 2 foraging workers from roadside quebrada at about 1000 m in degraded forest remnant, 7 and 16 February 1975, leg. W. L. and D. E. Brown. Holotype in MCZ-Cambridge, paratypes in MCZ, CUIC-Ithaca, BMNH-London. Coll. J. Lattke, Caracas.