Strumigenys dexis

Known from rainforest, montane forest and littoral forest, all of the records of this species have been collected from litter samples.

Identification
Bolton (2000) - A member of the dexis complex in the Strumigenys dexis-group. Within the group dexis is related to Strumigenys coveri, Strumigenys gorgon, Strumigenys peyrierasi and Strumigenys rabesoni, a complex of five species that share a distinctive form of sculpture in which cephalic and promesonotal punctures are spaced out and separated by areas of smooth cuticle, rather than having the entire surface opaque and blanketed with reticulate- punctate sculpture (promesonotal punctures absent in Strumigenys carolinae). Of these five species dexis is identified by its relatively short mandibles, broad head and unique labrum, where both anterior lobes sport a single fan-like lamella of very thin translucent cuticle that projects anteriorly. In addition:

1 The petiole node in coveri is as long as or longer than broad in dorsal view (distinctly broader than long in dexis).

2 The head has large spoon-shaped hairs on the dorsum of the occipital lobes in gorgon (absent in dexis).

3 The punctate sculpture of the vertex is much denser and more crowded in rabesoni than in dexis.

4 The mesonotum has a single pair of short straight standing hairs in peyrierasi (absent in dexis).

The presence of dense blanketing reticulate-punctate sculpture on the dorsum of the head distinguishes the sylvaini-complex from dexis and its immediate allies discussed above. Beside the sculpture Strumigenys alperti and carolinae have a unique distribution of scale-like hairs anteriorly on the cephalic dorsum, and Strumigenys sylvaini and Strumigenys wardi have standing hairs on the head and body, neither of which occurs in the four species of the dexis-complex.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  dexis. Strumigenys dexis Fisher, in Bolton, 2000: 641, figs. 387, 412 (w.) MADAGASCAR.

Worker
Holotype. TL 2.4, HL 0.66, HW 0.57, CI 88, ML 0.12, MI 18, SL 0.29, SI 51, PW 0.36, AL 0.68. Characters of dexis-complex. Transverse edge of the depressed proximodorsal area of mandible with a short row of curved spoon-shaped hairs approximately the same as those fringing the upper scrobe margin. Each labral lobe terminates anteriorly in a broad fan-shaped lamella of thin translucent cuticle and a short trigger-hair mesad of fan-like lamella; trigger-hairs often difficult to see. Clypeal dorsum with minute appressed hairs, the lateral margins with a short row of anteriorly curved large spoon- shaped hairs. Upper scrobe margin in full-face view with a continuous row of anteriorly curved spoon-shaped hairs that are similar to those on the leading edge of the scape; the row ends at the apex of the scrobe and does not extend onto the side of the occipital lobe. Eye with 7 ommatidia in total. Cephalic dorsum without standing hairs of any description but with scattered minute flattened appressed hairs present. Area of cuticle within antennal scrobe densely reticulate-punctate except for extreme posterior portion which is superficially reticulate to smooth. Dorsum of head behind clypeus with separated shallow punctures, the spaces between them shining; ventral surface of head unsculptured. Pronotum in dorsal view with strongly convex sides, appearing very short and broad. Flattened dorsum of pronotum sculptured as vertex; pleurae and sides of propodeum smooth and shining; propodeal declivity with a band of fine punctate sculpture between the teeth. Lamella of propodeum broad and sinuate, apices of propodeal teeth free. Dorsal surfaces of alitrunk, waist segments and first gastral tergite without standing hairs, but minute appressed flattened hairs are sparsely present everywhere except on first gastral tergite. Base of first gastral sternite and posterior margins of petiole and postpetiole, with a row of flat, broad, spatulate appressed hairs. Petiole node in dorsal view broader than long, with extensive lateral spongiform lobes. Disc of postpetiole completely surrounded by spongiform tissue in dorsal view; sides and posterior margin of the disc forming a single convex arc and the disc with scattered but easily visible punctures upon a smooth surface. In profile all spongiform lobes of the waist segments well developed. Legs with spatulate to scale-like hairs present, but without standing pilosity.

Paratypes. TL 2.4-2.5, HL 0.65-0.66, HW 0.58-0.59, CI 88-90, ML 0.12-0.13, MI 18-20, SL 0.29, SI 49-50, PW 0.36-0.37, AL 0.68 (2 measured). As holotype.

Members of these series tend to be a little larger than the type-series and to have the head fractionally broader, HL 0.68-0.70, HW 0.63-0.64, CI 90-93, ML 0.12-0.13, MI 17-19, but otherwise match the types perfectly.

Type Material
Holotype worker, Madagascar: 45 km. S Ambalavao, 22°13'S, 47°01'E, 785 m., 25.ix.1993, sifted litter (leaf mold, rotten wood), rainforest, #696 (40)-6 (B. L. Fisher).

Paratypes. 1 worker with same data as holotype; 1 worker with same data but #696 (20)-9.

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.