Strumigenys sphera

Common within its range, S. sphera is a wet forest species. The bulk of many collection records support it being a litter/ground dwelling species. Some specimens have been found in rotten wood.

Identification
Fisher (2000) - A member of the sphera complex in the Strumigenys arnoldi-group. The non-paratypic material exhibits variation in body size, eye size, hair shape, and depth of ventral petiolar spongiform tissue. This variation is present within and between localities and is very suggestive that these specimens may represent a complex mosaic of several distinct sibling species. For example, within R. S. Andringitra, 3 forms are represented. At 785 m., specimens have the following characters that are distinct within Andringitra: in profile hairs on mesonotum, petiole, postpetiole and gaster coarsely remiform to thickly clavate. Eyes larger; with head in profile, maximum width of eye along horizontal axis greater than width of preocular groove immediately anterior of eye along same axis. At 1275 m. in Andringitra the type-specimens of sphera are found which have small eyes and narrowly clavate hairs (HL 0.92-0.99, HW 0.74-0.80); a third form is also found at 1275 m. that is identical to the type-specimens of sphera in all diagnostic characters except they are smaller (HL 0.70-0.80, HW 0.56-0.67). In addition, a fourth form was collected at Manongarivo and Anjanaharibe. These specimens have a reduced spongiform strip on the petiole. In profile the ventral petiolar spongiform tissue is not developed into an expanded curtain that extends the length of the peduncle. At most the ventral petiolar spongiform tissue forms an irregular, very narrow strip, maximum depth of spongiform tissue much less than half the maximum width of eye.

The problem with the geographic variation of sphera is that although the variation is discrete within R. S. Andringitra, the variation is continuous when other localities are included. Additional collections and new characters will have to be studied before we are confident of the boundaries of this species.

S. sphera is distinguished from other members of the sphera-complex by the following combination of characters: 1 Anterior margin of mesonotum with only a single pair of erect hairs, situated at anterior lateral margin of mesonotum. 2 Upper scrobe margin without a broad lamellate rim or flange throughout its length, lamellate rim when present limited to region above antennal insertion. 3 Basal half of scape never sharply swollen, scape more or less subcylindrical.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  sphera. Strumigenys sphera Fisher, in Bolton, 2000: 668, figs. 398, 418 (w.q.) MADAGASCAR.

Worker
Holotype. TL 3.8, HL 0.95, HW 0.77, CI 82, ML 0.56, MI 60, SL 0.68, SI 88, PW 0.41, AL 0.95. Characters of sphera-complex. Each mandible with 1 preapical tooth, situated in the apical third. Upper scrobe margin not bordered by a projecting laminar rim throughout its length, eyes clearly visible in full-face view. Eye small, convex, maximum diameter of eye equal to or slightly greater than maximum width of scape. Scape long and slender, subcylindrical, narrowed near base, approximately straight; hairs on leading edge narrowly spatulate. Cephalic dorsum clothed with curved spatulate to narrowly spoon-shaped ground-pilosity; upper scrobe margin with hairs that are similar in size and shape to those on the dorsum. Cephalic dorsum with a transverse row of 2 (rarely 3) pairs of stout filiform hairs close to the occipital margin and 1 pair of erect hairs on vertex. Dorsum of head reticulate-punctate with superimposed rugulose sculpture that extends to the apex of occipital corners. Pronotal humeral hair absent; humeral angles rounded, posterolateral margin of pronotum with a small raised welt. Anterior margin of mesonotum with 1 pair of stout standing hairs which are slightly thickened apically. Propodeum with 1 pair of short, posteriorly curved narrowly spatulate hairs immediately anterior or at base of propodeal spines. Midsection of the lateral margins of propodeal declivity with 1 or 2 pairs of fine projecting hairs. Ground-pilosity on alitrunk dorsum as on head, concentrated on promesonotum. Dorsum of alitrunk in outline convex anteriorly, posterior mesonotum sharply depressed, propodeum flat to gradually sloping to declivity. Metanotal groove represented by a shallow impression. Propodeal spines narrowly triangular, almost spiniform in some specimens, margins often spongiform; propodeal lamella absent or at most very narrow on apical portion of declivity. Alitrunk dorsum and sides of pronotum densely reticulate-punctate, dorsal promesonotum with faint rugulose sculpture. Pleurae mostly smooth and shiny with reticulate-punctate sculpture peripherally.

Petiole node in dorsal view slightly longer than broad. Postpetiole disc with longitudinally striolate sculpture on a fine punctulate surface, portions of central disc more or less smooth in some type-material. In profile ventral spongiform tissue of petiolar peduncle a narrow curtain that is continuous along the base of the peduncle, depth of curtain is slightly less than the maximum width of eye. Ventral spongiform tissue of postpetiole moderately developed. Basigastral costulae sharply defined. Dorsal surface of petiole, postpetiole, and gaster with feebly to narrowly clavate hairs. Colour yellowish brown to medium brown.

Paratypes. TL 3.7-3.9, HL 0.92-0.99, HW 0.74-0.80, CI 78-82, ML 0.55-0.57, MI 56-59, SL 0.66-0.71, SI 86-93, PW 0.40-0.41, AL 0.93-0.98 (10 measured). As holotype.

The non-paratypic material exhibits enormous size variation: HL 0.66-1.06, HW 0.51-0.88, CI 73-86, ML 0.36-0.63, MI 47-62, SL 0.45-0.77, SI 78-101 (72 measured).

Type Material
Holotype worker, Madagascar: 40 km. S Ambalavao, Res. Andringitra, 22°13'S, 46°58'E, 1275 m., 15.x.1993, sifted litter (leaf mold rotten wood), montane rainforest #793 (38)-8 (B. L. Fisher).

Paratypes. 11 workers and 2 queens (dealate) with same data as holotype but coded (1)-8, (2)-7, (3)-6, (4)-8, (16)-6, (20)- 10, (19)-8, (38)-8.

References based on Global Ant Biodiversity Informatics

 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.
 * Fisher, B. 2002. Ant diversity patterns along an elevational gradient in the Reserve Speciale de Manongarivo, Madagascar. in Gautier, L. and S.M. Goodman, editors, Inventaire Florestique et Faunistique de la Reserve Speciale de Manongarivo (NW Madagascar)
 * Goodman S., Y. Anbdou, Y. Andriamiarantsoa, B. L. Fisher, O. Griffiths, B. Keitt, J. J. Rafanomezantsoa, E. Rajoelison, J. C. Rakotonirina, L. Ranaivoarisoa et al. 2017. Results of a biological inventory of the Nosy Ankao island group, Parc National de Loky-Manambato, northeastern Madagascar. Malagasy Nature, Association Vahatra, 2017, 11, 