Pheidole retivertex

This species inhabits well-developed lowland forests, and nests in rotting wood blocks and twigs, and stores up a number of tiny seeds in its nest (Eg97-BOR-411). I have never encountered colonies which include more than one dealate queen. (Eguchi 2001)

Identification
Eguchi (2001) - P. retivertex is closely related to Pheidole nodgii, Pheidole magrettii, Pheidole tjibodana, Pheidole sayapensis and several undescribed species, and all these are peculiar among Indo-Chinese and Indo-Malayan congeners in having the combination of the characteristics noted under P. tjibodana. This species is most closely related to P. magrettii, but in the latter head and alitrunk of the minor are distinctly punctured. This species is also easily distinguished from two Bornean relatives, P. tjibodana and Pheidole sayapensis, by the characters given in the key.

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

Worker
Minor

Nomenclature

 *  retivertex. Pheidole retivertex Eguchi, 2001b: 104, fig. 42 (s.w.q.m.) BORNEO.

Worker
Major (n=5): TL 2.5-2.8 mm, HL 1.34-1.54 mm, HW 1.20-1.39 mm, SL 0.62-0.70 mm, FL 0.73-0.82 mm, CI 89-92, SI 48-52, PI 58-61. Head with almost parallel sides (Fig. 42A); head in profile not impressed on vertex (Fig. 42B). Hypostoma with a large median process. Clypeus with a median longitudinal carina, with anterior margin concave medially. Eye situated at about 1/3 distance of head (as measured from the mid-point of a transverse line spanning the anteriormost and posteriormost projecting points, respectively); distance between mandibular insertion and anterior margin of eye 1.7-2.0 times as long as maximal diameter of eye. Frontal carina well developed, horizontal, extending backward to 2/3 distance of head (Fig. 42A). Antennal scrobe overhung by frontal carina. Antenna with 3-segmented club; scape extending backward to about 3/5 distance of head; terminal segment ca. 1.2 times as long as preceding two segments together. Masticatory margin of mandible with apical and pre apical teeth, and a denticle in front of basal angle. Promesonotal dome with a small or inconspicuous prominence on its posterior declivity (Fig: 42C); each dorsolateral portion of the dome weakly produced outward. Mesopleuron with an inconspicuous transverse impression. Propodeal spine straight and acute, 2.5-3 times 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 emarginate at apex. Postpetiole 2.0-2.2 times as broad as petiolar node, in dorsal view angulate laterally.

Frons and gena longitudinally rugose; vertex, and dorsal and lateral faces of occipital lobe reticulate, with enclosures smooth and shining or very weakly punctured; promesonotum weakly reticulate with smooth and shining enclosures dorsally, and very weakly punctured or puncto-rugose laterally; upper part of mesopleuron irregularly reticulate; lower part of mesopleuron smooth and shining; lateral face of propodeum weakly punctured, or smooth and shining; lateral faces of petiole and postpetiole punctured weakly and dull; dorsa of petiole and postpetiole, and gaster smooth and shining. Outer face of mandible sparsely covered with very short appressed hairs (≤ 0.02 mm in length), which are much shorter than distance between piligerous punctures; submarginal zone of masticatory margin of mandible with a row of longer decumbent hairs. Head and alitrunk brown to reddish-brown, with darker clypeus; waist, gaster, antennae and legs yellowish-brown or light brown.

Minor (n=5): TL 1.9-2.0 mm, HL 0.58-0.62 mm, HW 0.57-0.60 mm, SL 0.56-0.61 mm, AL 0.83-0.91 mm, FL 0.61-0.66 mm, CI 97-98, SI 96-103, FI 104-112. Head in full-face view at most very weakly concave posteriorly (Fig. 42D); occipital carina very weak dorsally on head. Clypeus with a median longitudinal carina, with anterior margin in full-face view slightly convex or truncate medially. Eyes situated at about midlength of head; distance between mandibular insertion and anterior margin of eye 0.8-1.0 times as long as maximal diameter of eye. Frontal carina and antennal scrobe present only around antennal insertion. Antenna with 3-segmented club; scape extending beyond posterior border of head by its l/6Iength; terminal segment ca. 1.1 times as long as preceding two segments together. Promesonotal dome without a distinct prominence on its posterior declivity (Fig. 42E). Mesopleuron without a transverse impression. Propodeal spine triangular, 1.5-2.0 times as long as diameter of propodeal spiracle. Petiole 1.4-1.5 times as long as postpetiole (excluding helcium); petiolar node in posterior view not emarginate at apex. Postpetiole in dorsal view subhexagonal, ca. 1.9 times as broad as petiole.

Clypeus almost smooth and shining; remainder of dorsum of head weakly rugoso-reticulate, with enclosures very weakly punctured; lateral face of head weakly reticulate; dorsum of promesonotum very weakly punctured, or almost smooth with several irregular rugulae; lateral face of promesonotum weakly punctured; remainder of alitrunk largely punctured and dull; lateral face of petiolar pedicel weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Head and alitrunk light brown; waist, gaster, antennae and legs yellowish-brown.

Type Material
Holotype Major, colony: Eg98-BOR-865, Sepilok forest, Sabah, E. Malaysia (Borneo), K. Eguchi leg., 1998, deposited in. Paratypes 5 majors, 12 minors, 2 queens and 1 male 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.
 * Eguchi K. 2003. A study on the male genitalia of some Asian species of Pheidole (Hymenoptera, Formicidae, Myrmicinae). Sociobiology 41: 317-355.
 * Pfeiffer M., D. Mezger, and J. Dyckmans. 2013. Trophic ecology of tropical leaf litter ants (Hymenoptera: Formicidae) - a stable isotope study in four types of Bornean rain forest. Myrmecological News 19: 31-41.
 * Pfeiffer M., and D. Mezger. 2012. Biodiversity Assessment in Incomplete Inventories: Leaf Litter Ant Communities in Several Types of Bornean Rain Forest. PLoS ONE 7(7): e40729. doi:10.1371/journal.pone.0040877
 * Pfeiffer M., and D. Mezger. 2012. Biodiversity Assessment in Incomplete Inventories: Leaf Litter Ant Communities in Several Types of Bornean Rain Forest. PLoS ONE 7(7): e40729. doi:10.1371/journal.pone.0041011
 * 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