Prionopelta subtilis

This common and widespread species is found in rainforest, montane rainforest, lowland rainforest, tropical forest, littoral forest, degraded forest, and marsh edge from 5–1325 meters of elevation. On the ground it has been collected from inside rotten logs and sticks, as well as under moss, rocks, logs, and in litter. It has also been collected from above-ground sites including canopy moss and leaf litter, as well as inside above-ground twigs and branches. (Overson and Fisher 2015)

Identification
Overson and Fisher (2015) - P. subtilis can be recognized by the following combination of characters: twelve antennal segments; minute, densely placed cephalic foveae with raised margins where foveae touch so that the entire head is covered in a delicate mosaic of connected foveae with ridges between; well-defined, uniformly narrow, coronal suture that swells above the level of the surrounding integument; shallow foveae on the pronotum are much larger than those on the head, and more widely spaced, with tiny punctures between.

P. subtilis is easy to recognize at a glance under high magnification once several individuals have been observed, as the very small and delicate foveae covering the entire surface of the head produce a unique visual appearance among the Malagasy Prionopelta. The only other confusable species with dense, directly adjacent foveae across the entire head (besides Prionopelta laurae, which would not be mistaken for P. subtilis) are Prionopelta seychelles, and some Prionopelta descarpentriesi. Unlike P. subtilis, P. seychelles does not possesses a coronal suture medially on the head. Some individuals of P. descarpentriesi have a dense pattern of touching foveae with a network of ridges between them across the entire head, but these foveae are much larger and deeper than in P. subtilis. Additionally, this trait in P. descarpentriesi is accompanied by sculpture on the pronotum that consists almost entirely of large foveae which are similar in size to those on the head, whereas P. subtilis has much larger foveae on its pronotum than on its head, and these foveae are interspersed with punctures.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  subtilis. Prionopelta subtilis Overson & Fisher, 2015: 135, figs. 3A, B, 9 (w.) MADAGASCAR.

Worker
(N=20). HL 0.47–0.57 (0.52); HW 0.39–0.45 (0.42); SL 0.26–0.32 (0.29); WL 0.5–0.67 (0.58); PetL 0.14–0.18 (0.16); PetW 0.19–0.26 (0.22); T1W 0.31–0.4 (0.35); CI 76.55–86.41 (80.5); PI 126.32–150.69 (139.98); SI 61.34–71.39 (68.14).

Posterior head margin slightly concave with a noticeable notch medially; cephalic foveae dense and minute; virtually no area of the head lacking foveae in full-face view except at the extreme posterolateral corners; median cephalic band devoid of foveae is thin, linear, and slightly but uniformly swells above the surrounding integument; apical tooth intermediate in length; foveae on the pronotum are shallow, as well as more widely spaced and obviously larger than those on the head, with punctures present between; mesonotum and propodeum consisting of shallow foveae and punctures; metanotal groove visible dorsally, and mesopropodeal suture strongly visible in lateral view.

Type Material
Holotype, pinned worker, MADAGASCAR, Toamasina, Montagne d’Anjanaharibe, 18.0 km 21° NNE Ambinanitelo, 15.18833°S, 49.615°E, 470 m, rainforest, sifted litter (leaf mold, rotten wood), BLF08002, 8.iii.2003 (B.L. Fisher et al.) (: CASENT0033641).

Paratypes, 23 pinned workers with same data as holotype (: CASENT0033585; CASC: CASENT0033582; CASENT0033586; CASENT0033588; CASENT0033590; CASENT0033591; CASENT0033596; CASENT0033597; CASENT0033598; CASENT0033599; CASENT0033600; CASENT0033601; CASENT0033603; CASENT0033606; CASENT0033610; CASENT0033611; CASENT0033613; CASENT0033614; CASENT0033615; CASENT0033644; : CASENT0033604; : CASENT0033584; : CASENT0033643).

Etymology
The name of this species comes from the Latin adjective meaning “fine”, “thin”, or “slender” and refers to the very delicate, net-like patterns produced by the sculpture on the head.