Strumigenys diux

A rainforest species that has been found in leaf litter and downed sticks.

Identification
Bolton (2000) - A member of the diux complex in the Strumigenys scotti-group. S. diux and Strumigenys doxa comprise the diux-complex, characterised by the presence of stiff filiform humeral hairs and the presence of one or more erect hairs at the apex of the scrobe. S. diux is easily distinguished from doxa and other species in the scotti-group by the absence of a fringe of curved hairs along the upper scrobe margin and the presence of a single stiff erect apicoscrobal hair. In addition, the pronotum is without hairs except for the humeral pair.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  diux. Strumigenys diux Fisher, in Bolton, 2000: 677 (w.q.) MADAGASCAR.

Worker
Holotype. TL 2.3, HL 0.57, HW 0.40, CI 69, ML 0.27, MI 48, SL 0.33, SI 82, PW 0.26, AL 0.60. Characters of diux-complex. Mandibles in full-face view with outer margins shallowly and evenly convex, width of mandible approximately constant from the level of the proximal preapical tooth to near the base. Upper scrobe margin evenly and shallowly convex in full-face view, not bordered by a rim or flange, the eyes clearly visible; apices of the upper scrobe margins confluent with the sides of the occipital lobes through an even curve, without an angle separating the two. Maximum diameter of eye slightly greater than maximum width of scape, with 5-6 ommatidia in longest row. Scape short and stout, shallowly and gently curved; hairs on leading edge narrow, slightly flattened or spoon-shaped apically. Ground-pilosity of cephalic dorsum sparse and inconspicuous narrowly spoon-shaped hairs, the upper scrobe margin without a fringe of hairs. Cephalic dorsum with 8 standing filiform hairs arranged in a transverse row of 4 close to the occipital margin, an erect pair close to highest point of vertex, and a laterodorsally projecting pair in apicoscrobal position. Pronotal humeral hair stiffly filiform; humeral angles rounded. Anterior margin of mesonotum with a pair of stiff filiform hairs. Propodeum with a pair of fine, posteriorly curved hairs immediately anterior of propodeal spines. Dorsal alitrunk without conspicuous ground-pilosity. Dorsum of alitrunk in outline convex anteriorly and more or less flat posteriorly; posterior portion of mesonotum only slightly depressed below the anterior margin of propodeum. Anterior mesonotum without a conspicuous ridge or narrow carina above the mesothoracic spiracle. Propodeal tooth broadly triangular and pointed apically; without a lamella on declivity. Alitrunk dorsum, petiole, and postpetiole disc densely and shallowly reticulate-punctate. Side of alitrunk smooth with only peripheral punctation present. Spongiform appendages of petiole consisting of a narrow ventral strip and a narrow posterior collar. Postpetiole in profile with the lateral lobe much reduced, obviously smaller than the ventral spongiform lobe, and the latter smaller than the exposed area of the postpetiole disc in profile. Lateral lobe of postpetiole, in dorsal view, only very slightly projecting beyond the lateral outline of the disc. Base of first gastral tergite with sharply defined short costulae with a narrow central clear area. Dorsal surfaces of petiole, postpetiole and gaster with standing filiform hairs. Colour dull brownish yellow.

Paratypes. TL 2.3-2.4, HL 0.55-0.59, HW 0.38-0.41, CI 67-72, ML 0.27-0.29, MI 47-50, SL 0.33-0.34, SI 80-86, PW 0.25-0.27, AL 0.59-0.63 (4 measured). As holotype.

Measurements of this material extend the range shown by the type-series: ML 0.25-0.27, SL 0.29-0.33 (9 measured). This material differs slightly in the diagnostic characters of the type-material. In specimens from Cap Masoala and Ambato, the ventral spongiform lobe of the postpetiole is often larger than the exposed area of the postpetiole disc in profile.

Type Material
Holotype worker, Madagascar: 6.9 km. NE Ambanizana, 15°34'S, 50°00'E, 825 m., 2.xii.1993, sifted litter (leaf mold, rotten wood), rainforest, #976 (28)-15 (B. L. Fisher).

Paratypes. 5 workers and 2 queens (dealate) with same data as holotype but coded (34)-14, (43)-10, (48)-15, (48)-17, (49)-11.