Pheidole spinicornis

This species seems to inhabit well-developed forests in lowlands and hill areas. It is completely sympatric with two of its supposed relatives, Pheidole quadricuspis and Pheidole quadrensis, in Sepilok forest. (Eguchi 2001)

Identification
Eguchi (2001) - Head and alitrunk of minors from Poring is weakly rugoso-reticulate with punctured and dull enclosures. Recognition P. spinicornis is closely related to Pheidole lokitae, Pheidole quadrensis, Pheidole sperata, Pheidole quadricuspis and Pheidole acantha, and several undescribed species (see under P. lokitae), but can be recognised among the five Bornean species by the characters given in the key.

Eguchi et al. (2016) - Distinction from P. leloi: In the major, promesonotal dome with a pair of spines which slightly or weakly curve backward, with a distinct transverse ridge on its posterior slope; first gastral tergite finely punctate over the surface. In the minor, propodeal spine horn-like, weakly downcurved; petiolar node in lateral view blunt at apex, and in posterior view not emarginate at apex.

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

Nomenclature

 *  spinicornis. Pheidole spinicornis Eguchi, 2001b: 116, fig. 48 (s.w.) BORNEO.

Worker
Major (n=5): TL 4.1-4.9 mm, HL 1.62-2.03 mm, HW 1.73-2.12 mm, SL 0.98-1.13 mm, FL 1.37-1.57 mm, CI 104-107, SI 54-59, FI 74-81. 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); posterior margin of head in full-face view flat, with a small emargination medially (Fig. 48A); head in profile not impressed on vertex (Fig. 48B). Hypostoma with a pair of stout median processes. Clypeus with a 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 1.6-1.8 times as long as maximal diameter of eye. Frontal carina inconspicuous, extending backward to about midlength of head. Antennal scrobe present only around antennal insertion. Antenna with 3-segmented club; scape extending backward to about 2/3 distance of head; terminal segment almost as long as preceding two segments together. Masticatory margin of mandible with apical and preapical teeth, and a denticle in front of basal angle. Promesonotal dome with a pair of spines which slightly or weakly curve backward; posterior declivity of the dome with a distinct prominence (Fig. 48C); the prominence in anterior view weakly concave medially. Mesopleuron with an inconspicuous transverse impression. Propodeal spine horn-like, weakly downcurved, 7-8 times as long as diameter of propodeal spiracle. Petiole cuneiform, 1.5-1.6 times as long as postpetiole (excluding helcium); petiolar node low, in posterior view not emarginate at apex; subpetiolar process very low, or almost absent. Postpetiole ca. 1.8-2.0 times as broad as petiolar node, in dorsal view angulate laterally, in profile right-angled anteroventrally.

Frons and gena longitudinally rugose; vertex, and dorsal and lateral faces of occipital lobe reticulate; alitrunk irregularly rugoso-reticulate; petiole (excluding its smooth and shining anteroventral face) punctured; postpetiole punctured, or punctured laterally and transversally rugose dorsally; dorsum of gaster punctured and dull. Outer face of mandible covered with decumbent hairs, which are 0.10-0.19 mm in length and longer than distance between piligerous punctures. Body (except in relatively teneral individuals) dark reddish-brown with lighter alitrunk.

Minor (n=6): TL 2.7-3.0 mm, HL 0.74-0.90 mm, HW 0.68-0.83 mm, SL 0.93-1.13 mm, AL 1.05-1.24 mm, FL 1.01-1.25 mm, CI 89-95, SI 127-139, FI 139-153. Head in full-face view oval (Fig. 48D), with distinct occipital carina. Clypeus with a weak median longitudinal carina, with anterior margin in full-face view slightly convex medially. Eyes situated at or behind midlength of head; distance between mandibular insertion and anterior margin of eye 1.0-1.2 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 margin of head by more than its 1/3 length; terminal segment ca. 0.9 times as long as preceding two segments together. Promesonotal dome with a pair of spines dorsolaterally, with an inconspicuous prominence on its posterior declivity (Fig. 48E). Mesopleuron without a transverse impression. Propodeal spine hornlike, weakly downcurved, ca. 5 times as long as diameter of propodeal spiracle. Petiole cuneiform, ca. 1.3 times as long as postpetiole (excluding helcium); petiolar node low, in posterior view not emarginate at apex. Postpetiole 1.9-2.2 times as broad as petiolar node.

Clypeus smooth and shining, sometimes with several rugulae; remainder of head smooth and shining dorsally and punctured laterally; alitrunk largely punctured and dull, but area between promesonotal spines occasionally smooth and shining; lateral faces of petiole and postpetiole weakly punctured; dorsa of petiole and postpetiole, and gaster smooth and shining. Body brown to reddish-brown, with darker gaster; antennae and legs a little lighter than alitrunk.

Type Material
Holotype Major, colony: Eg98-BOR-880, Sepilok forest, Sabah, E. Malaysia (Borneo), K. Eguchi leg., 1998, deposited in. Paratypes 8 majors and 12 minors from the same colony to which the holotype belongs, deposited in, , , , , , and UMS.

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. 2001. A revision of the Bornean species of the ant genus Pheidole (Insecta: Hymenoptera: Formicidae: Myrmicinae). Tropics Monograph Series 2: 1-154.
 * Eguchi K., B. Tuan Viet, E. Oguri, and S. Yamane. 2016. The first discovery of the “Pheidole quadricuspis group” in the Indo-Chinese Peninsula (Insecta: Hymenoptera: Formicidae: Myrmicinae). Revue suisse de Zoologie 123(1): 45-55.
 * Ohasi M., Y. Maekawa, Y. Hashimoto, Y. Takematsu, S. Hasin, and S. Yamane. 2017. CO2 emission from subterranean nests of ants and termites in a tropical rain forest in Sarawak, Malaysia. Applied Soil Ecology 117–118: 147–155.
 * 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.