Strumigenys heterodonta

Lattke and Aguirre (2015) - With the discovery of Strumigenys lojanensis (now Strumigenys onorei) it is possible to discern a group of 5 northern andean species of the gundlachi complex with a preference for cold forests above 2000 m altitude, where the presence of most ants is negligible (Longino, 2014). The other species are Strumigenys enopla, known from altitudes between 1900 and 2200 m in SW Colombia, Strumigenys nubila, sampled from altitudes between 2000 and 2500 m in Colombia and Venezuela, Strumigenys vartana, a Colombian species known from altitudes between 1800 and 2530 m and Strumigenys heterodonta which was recently described from 2940 m altitude in Ecuador (Rigato & Scupola, 2008).

Identification
Rigato & Scupola (2008) - A member of the gundlachi-complex of the Strumigenys gundlachi group. Strumigenys osellai and Strumigenys heterodonta from Ecuador are assigned to the Strumigenys gundlachi-group because of their long mandibles, and to the S. gundlachi-complex because of their long trigger hairs, the presence of just 2 intercalary denticles between apical mandibular teeth and absence of a large preapical denticle around the midlength of each mandible. Both species differ from other members of the complex for their preapical mandibular dentition and some minor characters and form a separate species cluster.

The preapical dentition of S. heterodonta separates it from S. osellai. The latter bears a higher number of elements, with two large ones and a smaller one very close to the apicodorsal tooth; S. heterodonta has just one large tooth on its mandibular shaft.

Distribution based on Regional Taxon Lists
Neotropical Region: Ecuador.

Nomenclature

 *  heterodonta. Pyramica heterodonta Rigato & Scupola, 2008: 479, figs. 4 6 (w.) ECUADOR. Combination in Strumigenys: unpublished.

Worker
Holotype. TL 2.8, HW 0.50, HL 0.66, CI 76, ML 0.41, MI 62, SL 0.41, SI 82, PW 0.35, AL 0.74.

Mandibles relatively long and narrow with 4 preapical teeth and denticles. The largest tooth is placed at the apical third of the mandible. Apical fork with two intercalary denticles. Labral lobes well developed but distinctly shorter than trigger hairs. Anterior clypeal border convex medially. Antennal scrobe moderately impressed. Postoral transverse groove visible in profile but not very deep.

Pronotum anteriorly delimited by a transverse carina marking a step above the cervical shield. Alitrunk in profile with a weakly convex promesonotum; mesonotum sloping very gradually to the nearly flat base of the propodeum. Mesonotum laterally bordered by a weak carina. Metanotal impression absent. Propodeal teeth strong; their posterior edges form a lamella bordering the propodeal declivity. Petiole with a dome-like node, slightly convex above and posteriorly delimited by a transverse lamella just before the insertion of the postpetiole. Postpetiole much wider than petiole; in profile slightly lower and weakly convex above. The postpetiolar tergite bears anteriorly a transverse spongiform carina and posteriorly a transverse spongiform lamella at the insertion of the gaster; this lamella laterally widens and becomes lobiform. Postpetiolar sternite with a well developed spongiform appendage, which is subtriangular in profile.

Gaster anteriorly with a transverse spongiform thin lamella fitting that of the postpetiolar tergite.

Sculpture. Head, alitrunk and waist mostly densely reticulate-punctate; meso- and metapleuron chiefly smooth and shining. Postpetiolar disc weakly sculptured, superficially reticulate-punctate and anteriorly extensively smooth and shining. Gaster smooth with very short longitudinal costulae basally.

Pilosity. Main erect setae on the body long and slightly clavate (remiform) and with the following arrangement: a pair apicoscrobal, two pairs on head dorsum (one on the vertex and one on the occiput), a humeral pair, a pair anteriorly on mesonotum; two pairs on the petiolar node; 8 hairs on the postpetiole arranged in two transverse rows. Gastral tergites bear several regularly arranged hairs. Ground pilosity (pubescence) sparse and slightly raised on head and alitrunk, a little more abundant on the appendages, including mandibles. Gastral sternites apically with long simple hairs, proximally the first sternite bears the usual transverse fringe of curled hairs. Anterior clypeal border fringed with spatulate hairs. Leading edge of scape with several standing, curved, simple to weakly spatulate hairs: the first two and the apical ones are bent toward the apex of the scape, setae 3 and/or 4 are bent toward the base.

Colour. Concolorous testaceous.

Paratype. TL 2.8-3, HW 0.49-0.51, HL 0.64-0.67, CI 75-78, ML 0.40-0.42, MI 61-64, SL 0.39-0.42, SI 78-84, PW 0.33-0.35, AL 0.71-0.75 (7 measured).

The preapical mandibular dentition is variable: minute denticles may either miss or be even more abundant. I could count 3 to 5 preapical teeth and denticles, but the most usual number is 4 on both mandibles. The two largest teeth are always present, although the minor apicalmost one can be quite reduced; also, any denticle between those two teeth often misses and basalmost denticles are usually 1 or 2, but they can be so minute to be hardly visible. Another variable character is the sculpture of the postpetiolar disc, which usually is mostly smooth and shining; yet a weakly reticulate-punctate sculpture can be moderately developed. The inclination of setae on the scape is somewhat consistent with at least one hair (usually n°4 from the base) curved toward the base.

Type Material
Holotype worker: ECUADOR, Pichincha, Pasochoa, 2940 m, 0°25’19” S – 78°30’57”W, 26.VII.2006, leg. G. Caoduro, A. Scupola, under bark.

Paratypes (7 workers): same data as the holotype ASPC, MSNV,,.

Etymology
From the Greek héteros, different, and odoús, odóntos, tooth, for its four mandibular preapical teeth and denticles all different in size from one another.

References based on Global Ant Biodiversity Informatics

 * Rigato F., and A. Scupola. 2008. Two new species of the Pyramica gundlachi-group from Ecuador (Hymenoptera Formicidae). Memoirs on Biodiversity 1:477-481.