Carebara silenus

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, Singapore. Oriental Region: Thailand.

Nomenclature

 *  silenus. Pheidole silenus Smith, F. 1858b: 176 (s.w.) SINGAPORE. Combination in Pheidologeton: Mayr, 1862: 751; in Carebara: Fischer, Azorsa & Fisher, 2014: 72. Senior synonym of speculifrons: Ettershank, 1966: 119.
 * speculifrons. Amauromyrmex speculifrons Wheeler, W.M. 1929b: 1, fig. 1 (w.) BORNEO. Junior synonym of silena: Ettershank, 1966: 119.

Worker
Wheeler (1929), for Amauromyrmex speculifrons - Length, 2.5-3.5 mm.

Head slightly longer than broad, as broad in front as behind, with evenly convex lateral borders and concave posterior border; occipital border marginate; vertex and gula in profile flattened, especially behind. Eyes consisting of less than a dozen unequal facets. Clypeus somewhat flattened in the middle, the anterior border with a small, indistinct median emargination. Mandibles with convex external borders, 6-toothed, the two apical teeth and the basal tooth large, the three remaining teeth very small, separated by a diastema from the second tooth and diminishing in size towards the base. Antennae slender; scapes straight, slightly enlarged towards their tips, which extend somewhat beyond the posterior corners of the head; first funicular joint about three times as long as broad; joints 2-8 distinctly longer than broad; club somewhat shorter than the remainder of the funiculus, its two joints rather slender, the basal narrower than the apical and about three-fourths as long. Thorax slender, decidedly narrower than the head, broadest through the pronotum; the meso- and epinotum narrow; pronotum slightly longer than broad, evenly elliptical from above, its dorsal surface depressed and moderately flattened, very feebly convex in profile; the pair of spines rather blunt, somewhat longer than broad at their bases, flattened and projecting outward and slightly forward and upward. From the base of each spine backward, the sides of the pronotum are distinctly marginate. The mesonotum seen from above is rectangular and parallel-sided, longer than broad; it gradually slopes downward and backward to the mesoepinotal constriction. Epinotum broader than the mesonotum, somewhat broader than long; its base moderatly convex in profile, longer than the declivity, which is vertical, marginate on the sides and rather concave medially; the spines are as long as their distance apart at the base, slender and acute, directed upward and outward and with their tips curved forward. Petiole very slender, nearly three times as long as broad, gradually broadened behind where it bears a rounded-conical node, through which the petiole is as high as the length of the peduncle; ventral surface evenly convex and finely crenulate in profile. Postpetiole fully half again as broad as the petiole, nearly one and one-half times as long as broad, subelliptical in profile, evenly convex above but decidedly lower than the petiolar node. Gaster smaller than the head, elongate elliptical, narrowed antteriorly. Distal halves of femora decidedly thickened, their bases and the tibial slender.

Feebly shining; mandibles subopaque, sharply and densely striate; front of head over a squarish area bounded anteriorly by the frontal carinae and as far back as the posterior fourth, very smooth and shining; remainder of head, thorax and petiole sharply and regularly reticulate-rugulose, the gula anteriorly and the cheeks with longitudinal rugre. The latter spread out fan-wise around the antennal foveae. There are rugae also on the thoracic dorsum but they are irregular, loose and vermiculate; sides of epinotum with several longitudinal rugae. Petiole more finely reticulate than the thorax. Postpetiole, gaster and legs shining but with rather uneven surface and with sparse piligerous punctures. Scapes and coxae indistinctly shagreened, less shining than the legs.

Hairs yellowish, coarse, sparse, pointed, of very uneven length; long and erect on the dorsal surface, especially on the pronotum, clypeus and gaster; shorter and oblique on the legs and scapes.

Mandibles, head, thorax and coxae deep reddish brown; petiole, post petiole, gaster, legs and antennae paler and more yellowish brown; first gastric segment, except anteriorly, dark brown.

Type Material
Pheidole silenus

One syntype worker major in, one syntype worker major in. Both labelled “SING.”