Strumigenys olsoni

Widely ranging across Madagascar, S. olsoni occurs in habitats that vary from grassland to rainforest. Most collections are from litter-samples, one is noted as being from a rotten stump.

Identification
The only member of the Strumigenys olsoni-group.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  olsoni. Pyramica olsoni Bolton, 2000: 353, figs. 223, 243 (w.q.) MADAGASCAR. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 125

Worker
Holotype. TL 2.3, HL 0.59, HW 0.42, CI 71, ML 0.11, MI 19, SL 0.24, SI 57, PW 0.25, AL 0.57. Dorsum of head with minute appressed hairs, in profile the vertex also with a few short erect simple hairs between the highest point and the occipital margin. Dorsolateral margin of head in full-face view with two short simple projecting hairs, the first the apicoscrobal and the second on the side of the occipital lobe. Upper scrobe margins more or less straight in full-face view, feebly divergent posteriorly and confluent with the sides of the occipital lobes; the latter strongly projecting posteriorly and with narrowly rounded posterior lobes. In profile the occipital lobe is narrow and projects strongly backwards. Clypeus and vertex polished, with minute, widely scattered small punctures that do not detract from the overall glossy appearance of the head. Eye with 5 ommatidia in its greatest diameter. Alitrunk and waist segments completely lacking sculpture, the first gastral tergite un sculptured except for the basigastral costulae that arise in two clusters, one on each side of a smooth median area. Dorsa of promesonotum, waist segments and first gastral tergite with numerous simple hairs that are erect or suberect. Pronotum evenly transversely convex, the dorsum in profile also convex. Petiole node in dorsal view slightly longer than broad, in profile the node with a free sloping posterior face. Disc of postpetiole twice broader than long in dorsal view, its anterior margin broadly shallowly concave, the sides shallowly convex and strongly convergent posteriorly.

In profile the postpetiole extremely narrow dorsoventrally, the sternite very reduced. Spongiform appendages of waist segments thin and lamelliform. Lateral appendages of petiole node in dorsal view a pair of thin, flap-like lobes, anterior collar of postpetiole a thin lamella. Ventral curtain of petiole in profile massive, as deep as the node is high. Lateral lobe of postpetiole a continuous flange, broadest posteriorly; ventral lobe small.

Paratypes. TL 2.2-2.3, HL 0.58-0.60, HW 0.42-0.44, CI 71-73, ML 0.10-0.11, MI 17-19, SL 0.23-0.25, SI 55-60, PW 0.24-0.26, AL 0.55-0.58 (6 measured).

Type Material
Holotype worker, Madagascar: 48 km. ENE Morondava, 20004'S, 44°39'E, 30 m., 5.i.1991, tropical dry forest (D.M. Olson).

Paratypes. 14 workers and 2 queens (dealate), with same data as holotype; 3 workers with same data but each dated 4-6.i.1991 on an upper label, and 4.i.1991 on a lower label; 5 workers with same data but 7.i.1991 (BMNH,, ).

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, 