Strumigenys chilo

Widely distributed in Madagascar rain forests, it occurs in other wet forest habitats as well. In addition to the many samples collected from litter samples, S. chilo has been found in downed logs and wood.

Identification
Bolton (2000) - A member of the chilo complex in the Strumigenys grandidieri-group. S. chilo is widely distributed in Madagascar rain forests and forms a close species pair with Strumigenys bibiolona within the grandidieri-group. They both have the mandibular apical fork subtended by a shorter third tooth, and the scrobe margin does not extend across the dorsal apex of the preocular groove so that the latter extends uninterrupted to the cephalic dorsum.

S. chilo is easily differentiated from bibiolona by the following characters: 1. Dorsum of head sharply depressed behind middorsum, forming a very shallow concave impression before occipital angles; in profile, outline of dorsal margin of occipital corners almost flat. 2. Propodeal spines shorter, length of spine about equal to distance between bases of spines, where distance between bases of spines is measured distal to basal curvature.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  chilo. Strumigenys chilo Fisher, in Bolton, 2000: 651, figs. 391, 415 (w.q.) MADAGASCAR.

Worker
Holotype. TL 3.2, HL 0.80, HW 0.61, CI 76, ML 0.45, MI 56, SL 0.56, SI 92, PW 0.33, AL 0.82. Characters of chilo-complex. Mandibles almost straight and at full closure parallel. Apical fork of mandible sub tended by a third, shorter spiniform tooth; the fork effectively 3-dentate; without intercalary teeth or denticles. Preapical teeth absent. Upper scrobe margin ends anterior of preocular groove; when viewed in profile, upper scrobe margin curves downwards at anterior margin of vertical preocular groove of side of head and forms a carina that almost meets preocular lamina; scrobe margin does not extend across dorsal apex of preocular groove so that the latter extends uninterrupted to the cephalic dorsum. Eye large, convex, and plainly visible in full-face view. Dorsum of head sharply depressed behind middorsum, forming a very shallow concave impression before occipital angles; in profile, outline of dorsal margin of occipital corners almost flat. Scape long and slender, approximately straight, the leading edge with a row of slender hairs which are slightly flattened or spoon-shaped apically. Cephalic dorsum with inconspicuous curved fine ground-pilosity; the upper scrobe margin without a row of hairs. Cephalic dorsum with 4 simple standing hairs arranged in a transverse row close to the occipital margin. Dorsum of head reticulate-punctate. Pronotum without standing hairs. Mesonotum with one pair of stout standing remiform to narrowly clavate hairs on anterior margin. Propodeum with one or two pairs of short, fine, posteriorly curved hairs immediately anterior of propodeal spines or on the basal third of the spines. Ground-pilosity on alitrunk as on head but sparser. With the alitrunk in profile the posterior portion of the mesonotum sharply depressed, the metanotal groove represented by a shallow impression. Pronotal humeri rounded to bluntly marginate. Lateral margin of posterior pronotum bluntly marginate. Anterior mesonotum without a narrow carina above the mesothoracic spiracle. Propodeal spines slender, almost spiniform; length of spines about equal to distance between base of spines, distance between base of spines measured distal to basal curvature; propodeal lamella absent. Alitrunk dorsum and sides reticulate-punctate. Petiole node in dorsal view reticulate-punctate and much longer than broad. Postpetiole disc reticulate-punctate. Spongiform appendages of petiole absent, extremely reduced on postpetiole but the latter with a spongiform collar. Basigastral costulae fine to superficial across base of gaster without a central clear area; gaster smooth and shiny where clean. Dorsal surfaces of petiole and postpetiole each with a pair posteriorly projecting stout hairs; gaster with stout standing hairs which are weakly swollen apically. Colour dull yellow to light brown.

Paratypes. TL 3.4-3.6, HL 0.85-0.90, HW 0.61-0.68, CI 71-77, ML 0.50-0.52, MI 58-60, SL 0.62-0.65, SI 94-103, PW 0.34-0.37, AL 0. 89-0.96 (4 measured). As holotype.

The non-paratypic material shows greater size variation than the type-series alone: HL 0.68-0.97, HW 0.50-0.72, CI 71-79, ML 0.40-0.55, MI 56-63, SL 0.47-0.67, SI 91-106 (12 measured), but otherwise matches all critical diagnostic characters.

Type Material
Holotype worker, Madagascar: 5.3 km. SSE Ambanizana, Andranobe, 15°40'S, 49°58'E, 425 m., 21.xi.1993, sifted litter (leaf mold, rotten wood), rainforest, #926 (23)-10 (B. L. Fisher).

Paratypes. 2 workers with same data as holotype but coded (27)-8, (11)-6; 2 workers and 1 queen (dealate) with same data as holotype but labeled 25.xi.1993, ex rotten log, rainforest, and coded #961.

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.