Strumigenys lojanensis

Identification
Lattke and Aguirre (2015) - Mandibles straight with small relatively same-sized 5-7 preapical denticles along anterior half; mandibular apex with two minute intercalary denticles that appear midway between upper and ventral apical teeth. Disc of postpetiolar dorsum weakly reticulate-punctate, spongiform processes of postpetiole well-developed. Head, most of mesosoma, coxae, femora and tibiae densely reticulate-punctate; katepisternum mostly smooth and shining.

This species fits quite well within the gundlachi complex as defined by Bolton (2000:176) but the spongiform processes of the postpetiole are much more developed in S. lojanensis. Within the gundlachi complex, S. lojanensis fits comfortably into the gundlachi species cluster, with the only difference consisting in the weaker reticulate sculpturing of the postpetiolar dorsum. Using the key to Neotropical Pyramica in Bolton (2000:137) specimens of S. lojanensis will flow directly to Strumigenys enopla. Using the description of S. enopla (Bolton, 2000: 185) and images of a Paratype from Antweb (CASENT0900177) it was possible to identify a number of discrete differences between the two species: The cephalic subdecumbent pilosity is not as arched and high as in S. enopla; the subdecumbent hairs on the mesosomal dorsum are also higher and more arched in S. enopla, as well as the standing hairs on petiole, postpetiole and gaster. The mesosomal dorsal margin of S. lojanensis is straight in lateral view, whilst in S. enopla it lojanensis than in S. enopla. There are 2 standing hairs on the petiolar dorsum of S. lojanensis, compared with 4 in S. enopla. In S. enopla the posterior edge of the spongiform sculpturing on the postpetiole is convex, but in S. lojanensis there is a distinct low median lobe.

The reticulate-punctate sculpture of the postpetiole is mostly strong and comparable to that of the petiole, covering most of it but weakens posteromedially on the dorsum, so it could be difficult to decide which way to go at couplet 7 of Bolton’s key. If the user decides for first option then the specimen will become stranded at couplet 9 due to the number of denticles, exceeding the maximum amount for either option. If the modification of Bolton’s key proposed by Rigato and Scupola (2008: 481) is used, then the specimen will key directly to Strumigenys osellai (Rigato & Scupola). In this case differences in the preapical dentition and metapleural sculpturing will permit easy separation: S. lojanensis bears only small denticles and never a large pair of denticles, plus the metapleuron in S. osellai is smooth and shining, but not so in S. lojanensis.

Distribution based on Regional Taxon Lists
Neotropical Region: Ecuador.

Nomenclature

 *  lojanensis. Strumigenys lojanensis Lattke & Aguirre, 2015: 176, figs. 1-3 (w.q.) ECUADOR.

Worker
Holotype (Paratypes, n=4): HL 0.62(0.60-0.63), HW 0.47(0.46-0.50), ML 0.49(0.48-0.50), SL 0.43(0.40-0.43), PW 0.31(0.31-0.34), AL 0.67(0.66-0.69) mm; CI 76(74-79), MI 79(76-82), SI 91(0.82-93). Posterior cephalic margin deeply concave, occipital lobes well developed; surface of cephalic dorsum transversely convex; anterior clypeal margin transverse, slightly sinuate with low median convex lobe. Dorsolateral margin of head with flagellate hair just posterad of eye level; cephalic dorsum with two pairs of slightly spatulate erect hairs, highest pair close to posterior cephalic border whilst shorter pair close to eye level. Leading edge of scape with slender hair at base that arches apicad, followed by 5 thicker, spatulate hairs: second hair from base arches apicad and is more slender than hairs 3-6, hairs 3-4 arch basad and hairs 5-6 usually arch apicad, though some specimens may have hair 6 arching towards base. Apical lobes of labrum clearly visible with mandibles closed, short and converge towards each other, slightly wider at base than at blunt apex; trigger hairs extend anterad to midpoint of mandibular length. Mandible straight, external margin straight to weakly convex, internal margin weakly sinuate, basally convex and apically concave, basal lamella convex; preapical denticles 5-6 on left mandible and 5-7 on right mandible with mandible pointing towards observer; denticles closest to apex usually larger though minute denticles or stubs may be present. Mandibular apex with two minute intercalary denticles that appear midway between upper and ventral apical teeth.

Mesosoma in lateral view with pronotal margin broadly convex, mesonotal to propodeal margin relatively flat. Transverse section of pronotal dorsum broadly convex; pronotal humeral hair fine and flagellate, sometimes forming apical loop; mesonotum with single pair of flagellate hairs; propodeal spiracle separated from posterior edge of propodeal lamella by over single width; propodeal tooth triangular, apex pointed. Propodeal tooth triangular, sharply pointed and slightly higher than basal length; metapelural lobe bluntly triangular, not higher than propodeal tooth. Petiole lacking spongiform processes, ventrum with low anterior lamella that extends posterad to midlength; spongiform sculpturing well-developed on postpetiolar ventrum and posterolaterally, vestigial strands of spongiform sculpturing usually present along anterior margin of abdominal sternite IV. Postpetiolar tergite with narrow lamella along anterior margin. Dorsum of abdominal segments II – V with series of straight to weakly arched hairs, all semi-erect over cuticular surface. Petiolar node with posterior pair, postpetiole with 3 pairs, two dorsal pairs and a lateral pair. Anterior border of abdominal tergite IV with transverse arched crest that parallels posteriorly projecting lamella of postpetiole, a few brief longitudinal costulae may be present along this crest; most of tergite smooth and shining with 20-24 erect, slightly arched, spatulate hairs and no appressed pubescence.

Head, most of mesosoma, petiole, postpetiole, coxae, femora and tibiae densely reticulate-punctate, sculpturing attenuated on discal area of postpetiolar node and along its anterior margin; katepisternum mostly smooth and shining with strip of reticulate-punctate sculpture along anteroventral and ventral margins, propodeal declivity mostly smooth and shining posteriorly; abdominal tergite IV smooth and shining. Body mostly dark brown, almost black; mandibles, antennae, and legs brown.

Queen
(Gyne 1 - Gyne 2): HL(0.62-0.64), HW(0.5-0.51), ML(0.51-0.48), SL(0.41-0.41), PW(0.38-0.39), AL(0.77-0.77) mm; CI(81-80), MI(82-75), SI(82-80). Besides the expected morphological differences the gyne is quite comparable to the workers except for the better developed petiolar ventral lamella, although still low it bears more resemblance to spongiform sculpturing whilst in the worker it is simply a brief, low lamella.