Pheidole tenebricosa

This species has so far been found from well-developed forests in Mt. Kinabalu (1500- 1800 m alt.). It nests in rotting wood on the ground, and occasionally stores up a number of tiny seeds in its nest (Eg97-BOR-393, 396). (Eguchi 2001)

Identification
Eguchi (2001) - P. tenebricosa is closely related to Pheidole maculifrons (known only from Philippines), Pheidole rugifera, Pheidole clypeocornis, Pheidole kikutai and Pheidole hortensis, and they are recognised among the congeners by the characteristics noted under P. hortensis. P. tenebricosa is very similar to P. rugifera among the species known from Borneo, and is distinguished from the latter by the characteristics noted under P. rugifera sp. nov.

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

Worker
Minor

Nomenclature

 *  tenebricosa. Pheidole tenebricosa Eguchi, 2001b: 121, fig. 51 (s.w.q.) BORNEO.

Worker
Major (n=5): TL 2.5-3.0 mm, HL 1.08-1.23 mm, HW 1.00-1.20 mm, SL 0.53-0.64 mm, FL 0.66-0.79 mm, CI 91-97, SI 50-58, FI 63-69. Head broadest at about 2/3 distance of head (as measured from the mid-point of a transverse line spanning the anteriormost and posteriormost projecting points, respectively) (Fig. 51A), in profile weakly impressed on vertex (Fig. 51B). Hypostoma bearing three median processes, of which lateral two are poorly developed. Clypeus occasionally with a weak median longitudinal carina, with anterior margin weakly concave medially. Eye situated at about 1/3 distance of head; distance between mandibular insertion and anterior margin of eye 1.4-1.8 times as long as maximal diameter of eye. Frontal carina horizontal, extending backward to about 2/3 distance of head (Fig. 51A). Antennal scrobe narrowly overhung by frontal carina. Antenna with 3-segmented club; antennal scape extending backward to 3/5-2/3 distance of head; terminal segment ca. 1.2 times as long as preceding two segments together. Masticatory margin of mandible with apical and preapical teeth, and two denticles in front of basal angle. Promesonotum forming a high dome, without a distinct prominence on its posterior declivity (Fig. 51C); each dorsolateral portion of the dome usually rather strongly produced outward. Mesopleuron divided by a weak transverse impression. Propodeal spine horn-like, usually blunt apically, almost twice as long as diameter of propodeal spiracle. Petiole 1.6-1.7 times as long as postpetiole (excluding helcium); petiolar node in posterior view not or hardly emarginate at apex. Postpetiole 1.4-1.5 times as broad as petiolar node.

Gena and anterior part of frons longitudinally rugose, with interspaces very weakly punctured and weakly shining; posterior part of frons, vertex, and dorsal and dorsolateral faces of occipital lobe reticulate, with punctured and dull enclosures; area between frontal carina and eye largely punctured and dull; outer face of mandible with rugulae only laterally around its base; dorsum of promesonotal dome coarsely reticulate, with weakly punctured enclosures; lateral face of promesonotum at least partly punctured or rugose; lower part of mesopleuron largely smooth and shining; remainder of alitrunk largely punctured; ventral faces of midcoxa and hindcoxa distinctly reticulate; lateral faces of petiole and postpetiole weakly punctured; dorsa of petiole and postpetiole, and gaster smooth and shining. Outer face of mandible sparsely covered with very short appressed hairs, which are 0.02-0.04 mm in length and much shorter than distance between piligerous punctures; submarginal zone of masticatory margin of mandible with a row of longer decumbent hairs. Body dark brown to blackish-brown; antennae and legs lighter than alitrunk.

Minor (n=5): TL 1.5-1.8 mm, HL 0.50-0.58 mm, HW 0.46-0.53 mm, SL 0.48-0.58 mm, AL 0.68-0.82 mm, FL 0.49-0.61 mm, CI 91-93, SI 103-109, FI 106-114. Head in full-face view weakly concave posteriorly (Fig. 510); occipital carina evanescent dorsally on head. Clypeus without a median longitudinal carina, with anterior margin in full-face view slightly convex medially. Eye situated just in front of midlength of head; distance between mandibular insertion and anterior margin of eye 0.9-1.0 times as long as maximal diameter of eye. Frontal carina and antennal scrobe present only around antennal insertion. Antenna with 3-segmented club; in full-face view scape extending beyond posterior border of head by about its 1/5 length; terminal segment 1.1-1.2 times as long as preceding two segments together. Promesonotal dome with a gentle posterior declivity which has no prominence (Fig. 51E). Mesopleuron without a distinct transverse impression. Propodeal spine 1-1.5 times as long as diameter of propodeal spiracle. Petiole ca. 1.6 times as long as postpetiole (excluding helcium); petiolar node in posterior view not or slightly emarginate at apex. Postpetiole 1.6-1.7 times as broad as petiolar node.

Dorsum of head above subocular level including clypeus punctured, and ventral face below the level smooth and shining; alitrunk punctured; lateral face of petiole weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Body colour pattern similar to that of the major.

Type Material
Holotype Major, colony: Eg97-BOR-394, Mt. Kinabalu (near the Headquarter), Sabah, E. Malaysia (Borneo), K. Eguchi leg., 1997, deposited in. Paratypes 18 majors, 19 minors and 1 queen from the same colony to which the holotype belongs, deposited in, , , , , , and UMS.

References based on Global Ant Biodiversity Informatics

 * Eguchi K. 2001. A revision of the Bornean species of the ant genus Pheidole (Insecta: Hymenoptera: Formicidae: Myrmicinae). Tropics Monograph Series 2: 1-154.
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58