Pheidole sabahna

This species inhabits well-developed lowland or hill forests. I found several colonies nesting in the soil at logging fronts near Ranau, Sabah. Heterick & Kitching (2022) collected this species in a pitfall trap within a lowland dipterocarp forest in Brunei.

Identification
This species and Pheidole quinata both have subcastes with a 5-segmented antennal club. They are well distinguished from each other by the characters given below.

Eguchi (2000):

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

Worker
Minor

Nomenclature

 *  sabahna. Pheidole sabahna Eguchi, 2000: 688, figs. 1-10 (s.w.m.) BORNEO. See also: Eguchi, 2001b: 108.

Worker
Eguchi (2001) - Major (n=15): TL 5.5-5.9 mm, HL 2.25-2.62 mm, HW 2.12-2.48 mm, SL 1.33-1.42 mm, FL 1.98-2.17 mm, CI 90-96, SI 56-63, FI 86-94. Head in full-face view 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. 44A); head in profile not impressed on vertex (Fig. 44B). Hypostoma with three low median processes. Clypeus with a median longitudinal carina medially, with anterior margin weakly emarginate medially. Eye situated at about 1/3 distance of head; distance between mandibular insertion and anterior margin of eye 1.9-2.0 times as long as maximal diameter of eye. Frontal carina and antennal scrobe present only around antennal insertion. Antenna with 5-segmented club (Fig. 44C); scape reaching about 2/3 distance of head. Promesonotal dome with a small prominence on its posterior declivity (Fig. 44D); the prominence in anterior view very weakly concave medially. Mesopleuron weakly divided by a transverse impression into upper and lower parts. Metanotal groove weak. Propodeal spine horn-like, straight, ca. 4 times as long as diameter of propodeal spiracle. Petiole in profile cuneiform, 1.1-1.2 times as long as postpetiole, bearing a low subpetiolar process (Fig. 44E); petiolar node in posterior view not, or slightly, emarginate at apex. Postpetiole in dorsal view subpentagonal, 1.8-2.0 times as broad as petiole, in profile strongly convex dorsally and almost flat ventrally.

Frons longitudinally rugose; vertex, occipital lobe and lateral face of head rugoso-reticulate, with enclosures very weakly punctured; alitrunk rugoso-reticulate excluding smooth declivitous face of propodeum; petiole (excluding smooth anterodorsal face) and postpetiole weakly punctured and dull; gaster smooth and shining. Body brown to reddish-brown, with darker gaster; legs a little lighter than alitrunk. Outer face of mandible sparsely covered with long decumbent hairs, which are 0.18-0.24 mm in length and, much longer than distance between piligerous punctures.

Minor (n=36): TL 3.5-3.7 mm, HL 0.88-1.08 mm, HW 0.78-0.93 mm, SL 1.15-1.41 mm, AL 1.30-1.58 mm, FL 1.33-1.69 mm, CI 83-89, SI 121-134, FI 165-193. Head in full·face view oval (Fig. 44F); occipital carina well developed. Clypeus with a median longitudinal carina, with anterior margin weakly emarginate medially. Eye situated at or in front of midlength of head; distance between mandibular insertion and anterior margin of eye ca. 1.3 times as long as maximal diameter of eye. Frontal carina and antennal scrobe present only around antennal insertion. Antenna with 5-segmented club (Fig. 44G); in full-face view scape extending well beyond posterior border of head by more than its 1/3 length. Promesonotum forming a relatively low dome, usually with a pair of low tubercles, and with a prominence on its posterior declivity (Fig. 44H). Mesopleuron sometimes with an inconspicuous transverse impression. Metanotal groove relatively deep (Fig. H). Propodeal spine horn-like, slender, directed upward, 6-7 times as long as diameter of propodeal spiracle. Petiole cuneiform, 1.0-1.1 times as long as postpetiole; petiolar node in posterior view not emarginate at apex. Postpetiole 2.0-2.2 times as broad as petiolar node.

Head including clypeus and promesonotum almost smooth and shining; remainder of alitrunk punctured distinctly (occasionally smooth and shining dorsally); petiole (excluding weakly punctured lateral face of pedicel) smooth and shining; postpetiole and gaster almost smooth and shining. In profile dorsum of promesonotal dome in front of the prominence on its posterior declivity bearing more than 20 standing hairs, and remainder of dorsum of alitrunk also bearing more than 20 standing hairs (Fig. 44H). Body brown to dark brown.

Male
TL 5.7-5.9 mm; HL 0.71-0.73 mm; HW 0.73-0.76 mm; SL 0.26-0.27 mm; maximum length of eye 0.41-0.42 mm; AL 2.21-2.30 mm; FL 1.80-1.87 mm; FWL 6.0-6.1 mm; CI 100-105; SI 35-37; FI 244-255.

Head in full face view narrowed behind eyes; in profile vertex strongly convex; occipital carina distinct. Eye elliptical, large, situated anterolaterally. Three ocelli well developed; the maximum diameter of median ocellus 0.9-1.0 times as long as distance between lateral ocelli. Clypeus in profile strongly convex anterodorsally; its anterior margin convex and entire; median portion with a longitudinal carina; clypeo-frontal suture indistinct. Distance between antennal insertions almost as long as maximum diameter of median ocellus. Antenna 13-segmented; scape cylindrical and slightly swollen apically, 3.0-3.2 times as long as broad; pedicel slightly longer than broad, 0.5 times as long as scape; 3rd antennal segment slightly narrower apically than basally, approximately 2.5 times as long as maximum width; 4-12th segments cylindrical and slender; terminal segment tapering apically, 1.3 times as long as scape. Mandible narrow, with a large apical tooth followed by several small teeth or denticles. Palp formula 2, 2. Alitrunk weakly sclerotized, sometimes deformed in dried specimens. Pronotum in dorsal view without humeri. Mesoscutum with very weak parapsidal furrows on its posterior half; axilla cuneiform; scuto-scutellar furrow broad and deep; mesoscutellum in dorsal view almost straight anteriorly, strongly convex posteriorly; mesopleuron divided into upper and lower parts by a weak transverse fullow. Metanotum located under the level of mesoscutellum, transverse. In profile dorsal and declivitous faces of propodeum meeting each other at an angle of 120-130°; propodeal spine absent; propodeal spiracle rounded, situated just in front of midlength and just above midheight of propodeum, directed posterolaterally. Metapleural lobe rounded. Forewing with radial, discoidal and two cubital cells; radial cell completely closed. Hindwing with 9-12 hamuli. Legs very long; hind femur 1.2-1.3 times as long as hind tibia; hind basitarsus almost as long as hind tibia. Petiole in dorsal view long, weakly widened in its posterior half, in profile weakly convex posterodorsally as a node, almost straight ventrally, without any indication of subpetiolar process. In dorsal view postpetiole slightly longer than broad; its anterior portion narrowed forward; in profile postpetiole weakly convex dorsally and almost straight ventrally; 2 out of 6 specimens examined with a long, slender, ventrally directed process on postpetiole, but the remainder without it. Gaster elliptical. Frons smooth and shining; the remainder of head finely rugose. Pronotum, most part of mesoscutum, upper part of mesopleuron smooth and shining; lower part of mesopleuron finely rugose; mesoscutellum reticulate; propodeum rugose, and punctured between rugae. Petiole and postpetiole weakly punctured and dull; gaster smooth and shining. Body with sparse erect or suberect hairs. Body yellow; vertex and dorsum of alitrunk weakly blackish.



Type Material
Eguchi (2001) - Holotype Major. Paratypes majors (7), minors (11) and males (4) (UMS,, , , , ). Logging area or. Kg. Yoshina, Ranau, Sabah, E. Malaysia (Borneo). K Eguchi leg.

References based on Global Ant Biodiversity Informatics

 * Berghoff S.M., U. Maschwitz, and K.E. Linsemair. 2003. Hypogaeic and epigaeic ant diversity on Borneo: evaluation of baited sieve buckets as a study method. Tropical Zoology 16: 153-163.
 * Eguchi K. 2000. Two new Pheidole species with a 5-segmented antennal club (Hymenoptera: Formicidae). Entomological Science 3: 687-692.
 * 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.0040879
 * 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.0041096
 * 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
 * Woodcock P., D. P. Edwards, R. J. Newton, C. Vun Khen, S. H. Bottrell, and K. C. Hamer. 2013. Impacts of Intensive Logging on the Trophic Organisation of Ant Communities in a Biodiversity Hotspot. PLoS ONE 8(4): e60756. doi:10.1371/journal.pone.0060756
 * Woodcock P., D. P. Edwards, T. M. Fayle, R. J. Newton, C. Vun Khen, S. H. Bottrell, and K. C. Hamer. 2011. The conservation value of South East Asia's highly degraded forests: evidence from leaf-litter ants. Phil. Trans. R. Soc. B. 366: 3256-3264.