Pheidole plinii

This species seems to inhabit well-developed lowland forests. Heterick & Kitching (2022) collected this species in the canopy of a lowland dipterocarp forest in Brunei.

Identification
Eguchi (2001a) - This species is characterised by a combination of the following conditions: occipital lobe of the major smooth and shining; posterior declivity of promesonotal dome having a distinct prominence in both the subcastes; the prominence in anterior view well concave medially in the major; promesonotal dome of the minor having a pair of low tubercles; head and promesonotum of the minor smooth and shining.

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

Worker
Minor

Nomenclature

 *  plinii. Pheidole plinii Forel, 1911a: 40 (s.w.q.) BORNEO. See also: Eguchi, 2001a: 19; Eguchi, 2001b: 92.

Worker
Eguchi (2001a) - Major (n=6): TL 2.5-3.2 mm, HL 1.12-1.29 mm, HW 1.11-1.23 mm, SL 0.69-0.73 mm, FL 0.84-0.93 mm, CI 95-99, SI 58-63, FI 74-79. Head broadest at 1/2-2/3 distance of head (as measured from the mid-point of a transverse line spanning the anteriormost and posteriormost projecting points, respectively) (Fig. 36A), in profile not impressed on vertex (Fig. 36B). Hypostoma with three low median processes, of which medianmost one is occasionally inconspicuous (Fig. 36C). Clypeus sometimes with a weak median longitudinal carina, with anterior margin emarginate medially. Eye situated at about 1/3 distance of head; distance between mandibular insertion and anterior margin of eye 1.3-1.5 times as long as maximal diameter of eye. Frontal carina weak, extending backward to 3/5-2/3 distance of head. Antennal scrobe inconspicuous, running along frontal carina. Antenna with 3-segmented club; scape slightly passing 2/3 distance of head; terminal segment ca. 0.9 times as long as preceding two segments together. Masticatory margin of mandible with apical and preapical teeth, and a small denticle in front of basal angle. Promesonotal dome with a distinct prominence on its posterior declivity (Fig. 36D); the prominence in anterior view well concave medially. Mesopleuron without a transverse impression. Propodeal spine ca. 3-3.5 times as long as diameter of propodeal spiracle. Petiole cuneiform, 1.0-1.1 times as long as postpetiole (excluding he1cium); petiolar node low, in posterior view not emarginate at apex. Postpetiole in dorsal view subpentagonal, 2.2-2.3 times as broad as petiolar node.

Frons and lateral face of head longitudinally rugose; occipital lobe largely smooth and shining; promesonotum largely smooth and shining, and with several transverse rugulae dorsally; mesopleuron, and lateral faces of propodeum and petiole weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Outer face of mandible sparsely covered with decumbent hairs, which are 0.06-0.09 mm in length and a little longer than distance between piligerous punctures. Body yellowish-brown; legs a little lighter than alitrunk.

Minor (n=7): TL 1.9-2.2 mm, HL 0.60-0.63 mm, HW 0.51-0.53 mm, SL 0.75-0.78 mm, AL 0.85-0.90 mm, FL 0.78-0.82 mm, CI 83-86, SI 145-152, PI 152-157. Head in full-face view oval (Fig. 36E); occipital carina well developed. Clypeus without a median longitudinal carina, with anterior margin in full-face view truncate medially. Eyes situated at about 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; scape extending beyond posterior border of head by a little more than its 1/3 length; terminal segment 0.8-0.9 times as long as preceding two segments together. Promesonotal dome with a pair of low tubercles, with a distinct prominence on its posterior declivity (Fig. 36F). Mesopleuron without a transverse impression. Propodeal spine elongate-triangular, ca. 2.5 times as long as diameter of propodeal spiracle. Petiole cuneiform, 1.1-1.2 times as long as postpetiole (excluding helcium); petiolar node low, in posterior view not emarginate at apex. Postpetiole 2.0-2.2 times as broad as petiolar node.

Head including clypeus and promesonotum smooth and shining; mesopleuron and propodeum punctured; lateral face of petiolar pedicel weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Body light brown with a little lighter alitrunk; legs a little lighter than alitrunk.

Type Material
Eguchi (2001b) - major, minor and queen; Singapore. Seven syntypes (3 majors, 3 minors and 1 queen, ) were examined, of which one major is designated as the lectotype.

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., and S. Yamane. 2003. Species diversity of ants (Hymenoptera, Formicidae) in a lowland rainforest, northwestern Borneo. New Entomol. 52(1,2): 49-59.
 * Hashimoto Y., Y. Morimoto, E. S. Widodo, and M. Mohamed. 2006. Vertical distribution pattern of ants in a Bornean tropical rainforest (Hymenoptera: Formicidae). Sociobiology 47(3): 697- 710.
 * Hashimoto Y., Y. Morimoto, and M. Mohamed. 2003. Species List of Ground and Leaf Litter Ants Collected in Lower Kinabatangan. Pp 13-18. In Lower Kinabatangan Scientific Expedition 2002, 176 pp. ISBN-13: 983-2369-11-8
 * Helms J. A., S. M. Helms, N. I. Fawzi, Tarjudin, F. Xaverius. 2017. Ant community of an Acacia mangium forest in Indonesian Borneo. Serangga 22(1): 147-159.
 * Ito, F.; Yamane, S.; Eguchi, K.; Noerdjito, W. A.; Kahono, S.; Tsuji, K.; Ohkawara, K.; Yamauchi, K.; Nishida, T.; Nakamura, K. 2001. Ant species diversity in the Bogor Botanic Garden, West Java, Indonesia, with descriptions of two new species of the genus Leptanilla (Hymenoptera, Formicidae). Tropics 10:379-404.
 * 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