Probolomyrmex curculiformis

Even though the new species was entirely collected by sifting litter, we suspect it is not a genuine leaf litter inhabitant. Instead, P. curculiformis is likely to be a hypogaeic species and the available material was sampled accidentally through the collection of soil for leaf litter sifting. A hypogaeic lifestyle would also explain the patchy distribution pattern. If true, intensive soil sampling in western Madagascar will likely yield more material of this species. The natural history of P. curculiformis is unknown.

Identification
Hita Garcia & Fisher (2014) - Probolomyrmex curculiformis is easily distinguishable from the other Malagasy congeners on the basis of the following character combination: head in full-face view around 1.5 to 1.6 times longer than broad (CI 62–65); SI 91–94; mesosomal outline straight without metanotal groove; hind tibia around 1.1 to 1.2 times shorter than head width (HTLI 83–92); petiole shorter, higher and stronger arched, in profile (without ventral process) between 1.0 to 1.2 times longer than high (LPNeI 107–116), in dorsal view petiole around 1.2 to 1.3 times longer than broad (DPeI 76–82).

Probolomyrmex curculiformis is unlikely to be confused with the other two Malagasy Probolomyrmex species. The shape of the petiole is fairly distinct and separates the western P. curculiformis from the northern Probolomyrmex tani since the latter species has a much lower and longer petiole than the first. The third species, Probolomyrmex zahamena, from eastern Madagascar shares a higher and stouter petiole with P. curculiformis. However, P. zahamena possesses a small, but distinct metanotal groove, which is absent in P. curculiformis. In addition, the two species also differ in head shape, which is slightly broader in P. zahamena (CI 67–70) than in P. curculiformis (CI 62–65). Nevertheless, the last difference is sometimes hard to observe and requires measuring.

Despite a very broad distribution pattern in western Madagascar, we could not observe any significant intraspecific variation except for surface sculpture. There is some moderate variation in density and depth of foveolate sculpture throughout the material examined here. Some specimens display very little sculpture while sculpture is very well developed in others.

Key to Madagascar Probolomyrmex

Distribution
Probolomyrmex curculiformis is widely but patchily distributed in western Madagascar. Its known distribution ranges from the southernmost localities Tsimanampetsotsa and Amboasary to Anabohazo in the northwest.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Habitat
Collection localities are all tropical dry forest or spiny forest habitats situated at very low elevations of 20 to 130 m.

Nomenclature

 *  curculiformis. Probolomyrmex curculiformis Hita Garcia & Fisher, 2014: 68, figs. 1B, 2C, D, 3C, 6 (w.) MADAGASCAR.

Worker
(N=15). HL 0.57–0.60 (0.59); HW 0.37–0.39 (0.38); SL 34–37 (0.35); WL 0.71–0.76 (0.74); PH 0.24–0.26 (0.25); PW 0.27–0.32 (0.30); HTL 0.32–0.35 (0.33); PeH 0.27–0.32 (0.29); PeNH 0.20–0.23 (0.21); PeNL 0.22–0.25 (0.24); PeW 0.18–0.19 (0.19); CI 62–65 (0.64); SI 91–94 (93); LMI 33–35 (0.34); HTLI 83–92 (88); DPeI 76–82 (79); LPeI 76–86 (80); LPeNI 107–116 (110); PeNI 60–67 (63).

In full-face view head between 1.5 to 1.6 times longer than broad (CI 62–65), posterior head margin more or less flat; lateral margins of head convex, broadest medially, posterolateral corners rounded; clypeus and anterior part of frons strongly protruding anteriorly as narrow frontoclypeal, subrectangular shelf or socket; antennal sockets exposed and closely approximated, separated by a thin, vertical lamella formed by fused frontal carinae; mandibles small, triangular to elongate-triangular, masticatory margin armed with one larger apical tooth and a series of six smaller denticles, in full-face view mandibles obscured by frontoclypeal shelf; palp formula 4,2; eyes absent; antennae 12-segmented, funicular antenommeres growing in size and width towards apex without forming well defined antennal club, apical antennomere much larger than remaining funicular antenommeres, antennal scape short (SI 91–94), far from reaching posterior head margin. Mesosoma slender, long, and relatively low (LMI 33–35), in profile mesosomal outline flat; propleurae enlarged and projecting ventrally; promesonotal suture and metanotal groove absent; declivitous face of propodeum margined by low, obtuse, and concave lamella on each side, propodeal lamella posterodorsally and posteroventrally with small, blunt tooth or rounded lobe; posterior declivity of propodeum weakly concave in dorsal view. Legs long and slender; all tibiae with single, pectinate spur; pretarsal claws simple without median tooth; hind tibia around 1.1 to 1.2 times shorter than head width (HTLI 83–92). In profile petiole with subpetiolar process around 1.2 to 1.3 times higher than long (LPeI 76–86), petiole without subpetiolar process around 1.1 to 1.2 times longer than high (LPNeI 107–116), petiolar dorsum strongly arched, much higher posteriorly, anterior face curving smoothly onto dorsum without well developed anterodorsal margin, posterior face vertical and concave, enclosed laterally and dorsally by low, thick carina; in dorsal view petiole around 1.3 to 1.3 times longer than broad (DPeI 76–82); pronotum between 1.5 to 1.7 times longer than petiolar width (PeNI 60–67); subpetiolar process well developed and lamelliform, ventral face weakly concave, anteroventral portion rounded to moderately angled, posteroventral portion sharper and stronger angled, projecting backwards, usually as small acute tooth. Abdominal segment III in profile narrowed anteriorly, broadest posteriorly. Sting well developed and very long. Surface sculpture generally weakly to moderately foveolate overlaying conspicuous very fine, more or less dense, coriaceous microsculpture, usually foveolate sculpture better developed and more conspicuous on cephalic dorsum, lateral mesosoma, and lateral petiole than remainder of body. Pilosity strongly reduced throughout and virtually absent, except for few short hairs below frontoclypeal shelf, some longer hairs on mandibles, and some short, fine hairs around metapleural gland orifice. Pubescence whitish, extremely fine, very short, and appressed, present over most of body, funicular antenommeres with such pubescence overlaid by much scattered, much longer, appressed hairs. Colour dark reddish brown, appendages light brown. Pilosity strongly reduced throughout and virtually absent, except for few short hairs below frontoclypeal shelf, some longer hairs on mandibles, and some short, fine hairs around metapleural gland orifice. Pubescence whitish, extremely fine, very short, and appressed, present over most of body, funicular antenommeres with such pubescence overlaid by much scattered, much longer, appressed hairs. Colour orange to light brown, appendages yellowish.

Type Material
Holotype, pinned worker, MADAGASCAR, Mahajanga, Parc National d’Ankarafantsika, Ampijoroa Station Forestière, 5.4 km 331° NW Andranofasika, 16.29889°S, 46.813°E, 70 m, tropical dry forest, sifted litter (leaf mold, rotten wood), collection code BLF03571, 26.III.–1.IV.2001 (Rabeson et al.) (: CASENT0469570). Paratypes, nine pinned workers with same data as holotype (: CASENT0469574; CASC: CASENT0469571; CASENT0469572; CASENT0469573; CASENT0469575; CASENT0469576; CASENT0469577; CASENT0469579; : CASENT0469578); and one pinned worker from Mahajanga, Parc National d’Ankarafantsika, Ampijoroa Station Forestière, 40 km 306° NW Andranofasika, 16.32083°S, 46.81067°E, 130 m, tropical dry forest, sifted litter (leaf mold, rotten wood), collection code BLF03522, 26.III.–1.IV.2001 (B.L. Fisher et al.).

Etymology
The name of the new species is a combination of the Latin noun “curculio”, which means weevil, and the suffix “formis”, which means alike. The long and narrow head with its anteriorly projecting frontoclypeal shelf resembles the elongated head shape of a weevil.