Strumigenys osellai

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

 *  osellai. Pyramica osellai Rigato & Scupola, 2008: 477, figs. 1-3 (w.q.) ECUADOR. Combination in Strumigenys: unpublished.

Worker
Holotype. TL 2.5, HW 0.45, HL 0.60, CI 75, ML 0.38, MI 63, SL 0.35, SI 78, PW 0.30, AL 0.65.

Mandibles relatively long and narrow with several preapical teeth and denticles: 7 on the left and 5 on the right; the right mandible lacks two of the smallest denticles. The distalmost preapical tooth is very close to the base of the apicodorsal teeth on both mandibles. The two largest teeth are at the apical third of each 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 profile with a convex promesonotum; mesonotum sloping gradually to the weakly convex base of the propodeum. Metanotal impression faint. Mesonotum and metanotal groove laterally marked by a weak carina. Propodeal teeth strong, slightly upturned and somewhat raised; their posterior edge forms a carina bordering the propodeal declivity. Petiole with a domelike 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 bluntly 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 and postpetiolar disc chiefly 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 are bent toward the apex of the scape, the following 2 or 3 are bent toward the base and the few remaining ones are bent toward the apex.

Colour. Body brown; mandibles, antennae and tarsi testaceous; coxae, femurs and tibiae light brown.

Queen
Paratype. TL 2.8, HW 0.49, HL 0.66, CI 74, ML 0.41, MI 62, SL 0.38, SI 78, PW 0.35, AL 0.75.

Mostly as the worker, and with the usual caste differences. Preapical mandibular dentition differs as follows: left mandible with 5 preapical teeth and denticles, right one with 6.When compared with worker’s mandibles the gyne keeps these consistent features: at least two close proximal denticles, well separated by the following two, relatively large, teeth on the distal third, and one minute denticle very close to the base of the apicodorsal tooth.

Propodeal teeth large and horizontal; their ventral edge form a conspicuous lamella running along the sides of propodeal declivity.

The female has 4 pairs of setae on the mesoscutum and 1 on the scutellum. Mesopleuron mostly smooth as in the worker; metapleuron with a small unsculptured patch only.

Type Material
Holotype worker: ECUADOR, Pichincha, Nanegalito, 0°03’ N – 78°41’ W, 1560 m, 27.VII.2006, leg. C. Bellò, G. Osella & M. Pogliano, collected by soil sifting in “bosque nublado”.

Paratype gyne: same data as the holotype.

Etymology
This species is dedicated to Prof. Giuseppe Osella, one of the collector's of this ant.