Pheidole quadricuspis

This species inhabits well-developed forests in lowlands. It nests in rotting twigs and wood blocks on the forest floor, and stores up a number of tiny seeds in its nest (Eg99-BOR-111). I have never encountered colonies which included more than one dealate queen. This species is sympatric with Pheidole quadrensis in Deramakot, Gunong Rara, Poring and Sepilok, Sabah, and Belalong and Merimbun, Brunei; and also sympatric with Pheidole spinicornis in Sepilok. (Eguchi 2001)

Identification
Eguchi (2001) - P. quadricuspis is most closely related to Pheidole lokitae, Pheidole quadrensis, Pheidole sperata, Pheidole acantha and Pheidole spinicornis, and several undescribed species (see under P. lokitae), but can be distinguished form the Bornean relatives by the characters given in the key.

Eguchi et al. (2016) - Distinction from Pheidole leloi: In the major, anterior part of vertex longitudinally rugose. In the minor, head almost completely smooth, with a few standing hairs; dorsal face of promesonotal dome smooth dorsomedially, and weakly punctate anterodorsally, laterally and posterodorsally; mesosoma lacking standing hairs; 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, Philippines. Oriental Region: Thailand.

Worker
Minor

Nomenclature

 *  quadricuspis. Pheidole quadricuspis Emery, 1900d: 683 (s.w.) INDONESIA (Sumatra). Combination in P. (Pheidolacanthinus): Emery, 1921f: 83. See also: Eguchi, 2001b: 98.

Eguchi (2001) - Two completely allopatric forms that differ in length and density of hairs on alitrunk of the major are recognised in the material examined. The minors of these two forms have no conspicuous standing hairs on alitrunk, and cannot be separated from each other. All majors from Borneo cited above uniformly bear a few very short standing hairs, while those from the southern Malay Peninsula and W. Sumatra bear longer standing hairs more densely (unfortunately my previous examination of the type material (Sumatra) did not focus on this character of the major). Further examinations of additional specimens from various localities (especially within Sumatra) and reexamination of the major in the type material are required in order to conclude their status (I tentatively treat them as conspecific). Moreover, minors which are similar to those of P. quadricuspis except in its hairy body have been collected from Kutai N. P., E. Kalimantan (4 minors, SKY, 1993) and Maninjau, W. Sumatra (5 minors, SNS). However, I omit them from the enumeration of specimens, because I have never examined majors coupled with the hairy minors and this did not allow me to conclude their status.

Worker
Eguchi (2001) - Major (n=10): TL 4.1-5.1 mm, HL 1.83-2.07 mm, HW 1.90-2.28 mm, SL 0.99-1.08 mm, FL 1.32-1.47 mm, CI 103-110, SI 47-53, FI 71-64. 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 almost flat, but slightly emarginate medially (Fig. 39A); head in profile not impressed on vertex (Fig. 39B). Hypostoma with a pair of stout median processes. Clypeus with a median longitudinal carina, with anterior margin in full-face view emarginate medially. Eye situated at about 1/3 distance of head;, distance between mandibular insertion and anterior margin of eye 1.7-2.0 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 2/3-3/4 distance of head; terminal segment 0.9-1.0 times 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, with a low or inconspicuous prominence on its posterior declivity (Fig. 39C); the prominence in anterior view not or very weakly concave medially. Mesopleuron with a transverse impression. Propodeal spine digitiform, with narrow base, weakly down-curved, 5-6 times as long as diameter of propodeal spiracle (Fig. 39C). Petiole cuneiform, 1.3-1.4 times as long as postpetiole (excluding helcium); petiolar node in posterior view emarginate at apex; subpetiolar process low; its anteroventral corner bluntly produced forward. Postpetiole 1.5-1.8 times as broad as petiolar node.

Frons and gena longitudinally rugose, with smooth and shining interspaces; occipital lobe reticulate, with smooth and shining enclosures; alitrunk irregularly rugoso-reticulate; petiole smooth and shining anterodorsally, rugose posterodorsally, and punctured laterally; postpetiole largely punctured, or punctured and dull laterally and transversely rugose dorsally; first gastral tergite rugose finely or punctured, and dull. Outer face of mandible sparsely covered with appressed hairs, which are 0.07-0.11 mm in length and shorter than distance between piligerous punctures; submarginal zone of masticatory margin of mandible with a row of longer decumbent hairs; alitrunk bearing a few very short standing hairs. Body reddish-brown to dark reddish-brown, with a little darker gaster; flagella and legs a little lighter than alitrunk.

Minor (n=5): TL 2.4-2.5 mm, HL 0.77-0.80 mm, HW 0.69-0.75 mm, SL 0.91-0.98 mm, AL 1.01-1.12 mm, FL 0.98-1.07 mm, CI 88-94, SI 130-138, FI 140-146. Head in full-face view oval; occipital carina distinct (Fig. 39D). Clypeus with a weak median longitudinal carina, with anterior margin in full-face view weakly convex medially. Eyes situated at or behind midlength of head; distance between mandibular insertion and anterior margin of head 0.9-1.1 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 more than its 1/3 length; terminal segment 0.9-1.0 times as long as preceding two segments together. Promesonotal dome with a pair of spines, without a prominence on its posterior declivity (Fig. 39E). Mesopleuron without a transverse impression. Propodeal spine elongate-triangular, 1.5 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 smooth and shining; promesonotum smooth and shining dorsally, and weakly punctured laterally; mesopleuron and propodeum punctured; lateral face of petiole weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Head with a few standing hairs (Fig. 39D); alitrunk lacking standing hairs (Fig. 39E); petiole, postpetiole and gaster very sparsely scattered with standing hairs. Body brown to dark brown (sometimes alitrunk is a little lighter than head and gaster).

Type Material
Eguchi et al. (2016) - ; Indonesia, Sumatra, Si-Rambé; E. Modigliani leg.; xii/1890-iii/1891 3 syntypes (1 major, 2 minor), CASENT0904267 and CASENT0905766.

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Donisthorpe H. 1947. Pheidole (Pheidolacanthinus) striatus sp. n. from New Guinea, with notes on the subgenus Pheidolacanthinus F. Smith (Hym., Formicidae). Entomologist's Monthly Magazine 83:172-174.
 * 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.
 * 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.
 * 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.
 * Emery C. Formiche raccolte da Elio Modigliani in Sumatra, Engano e Mentawei. Annali del Museo Civico di Storia Naturale 40: 661-722.
 * Emery, C. "Formiche raccolte da Elio Modigliani in Sumatra, Engano e Mentawei." Annali del Museo Civico di Storia Naturale Giacomo Doria (Genova) (2) 20, no. 40 (1900): 661-722.
 * Fayle T. M., E. C. Turner, J. L. Snaddon, V. Khen Chey, A. Y. C. Chung, P. Eggleton, and W. A. Foster. 2010. Oil palm expansion into rain forest greatly reduces ant biodiversity in canopy, epiphytes and leaf-litter. Basic and Applied Ecology 11: 337345.
 * Fayle T.M., Bakker, L., Cheah, C., Ching, T.M., Davey, A., Dem, F., Earl, A., Huaimei, Y., Hyland, S., Johansson, B., Ligtermoet, E., Lim, R., Lin, L.K., Luangyotha, P., Martins, B.H., Palmeirim, A.F., Paninhuan, S., Rojas, S.K., Sam, L., Sam, P.T.T., Susanto, D., Wahyudi, A., Walsh, J., Weigl, S., Craze, P.G., Jehle, R., Metcalfe, D. & Trevelyan, R. 2011. A positive relationship between ant biodiversity (Hymenoptera: Formicidae) and rate of scavenger-mediated nutrient redistribution along a disturbance gradient in a south-east Asian rain forest. Myrmecological News 14: 5-12.
 * 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.
 * Jaitrong W.; Nabhitabhata, J. 2005. A list of known ant species of Thailand. The Thailand Natural History Museum Journal 1(1): 9-54.
 * 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.0040785
 * 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
 * Sukimin S., M. Mohamed, and H. Aris. 2010. Ant diversity of Maliau Basin Conservation Area, Sabah, Malaysia. Journal of Tropical Biology and Conservation 6:89-101.