Pheidole deltea

Heterick & Kitching (2022) collected this species in a pitfall trap within a lowland dipterocarp forest in Brunei.

Identification
Eguchi (2001) - This relatively small-sized species is recognised among Indo-Chinese and Indo-Malayan congeners by a combination of the following characteristics: occipital lobe of the major smooth and shining; posterior declivity of promesonotal dome lacking a distinct prominence in both the subcastes; dorsal outline of propodeum almost continuous and straight in profile in both the subcastes; propodeal spine of the minor elongate-triangular, 3.5-4 times as long as diameter of propodeal spiracle.

Inter-colonial size variation has been observed. Majors from Eg96-BOR-374 (type material, collected from Gunong Rara) and Eg96-BOR-189 (Danum Valley) are relatively large in size, and their hypostoma has three median processes, of which medianmost one is much reduced.

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

Worker
Minor

Nomenclature

 *  deltea. Pheidole deltea Eguchi, 2001b: 47, fig. 13 (s.w.q.) BORNEO.

Worker
Major (n=9): TL 1.7-2.5 mm, HL 0.80-1.24 mm, HW 0.74-1.13 mm, SL 0.39-0.54 mm, FL 0.46-0.71 mm, CI 90-95, SI 46-54, FI 59-64. Head broadest at 3/5-2/3 distance of head (as measured from the mid-point of a transverse line spanning the anteriormost and posteriormost projecting points, respectively (cf. Fig. 2A)) (Fig. 13A), in profile not or slightly impressed on vertex (Fig. 13B). Hypostoma with three median processes, of which medianmost one is sometimes poorly developed (as seen in the type material). Clypeus without a median longitudinal carina, with anterior margin emarginate medially. Eye situated at about 3/10-1/3 distance of head; distance between mandibular insertion and anterior margin of eye 1.4-1.7 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 backward to 1/2-3/5 of head; terminal segment 1.1-1.2 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 an inconspicuous prominence on its posterior declivity (Fig. 13 C). Mesopleuron with an inconspicuous transverse impression. Dorsal outline of propodeum almost continuous and straight in profile (Fig. 13C); propodeal spine broadly based, 2.5-3.5 times as long as diameter of propodeal spiracle. Petiole cuneiform, 1.1-1.3 times as long as postpetiole (excluding helcium); petiolar node in posterior view not or slightly emarginate at apex. Postpetiole in dorsal view subhexagonal, 1.8-2.2 times as broad as petiolar node.

Dorsal and lateral faces of head excluding vertex and occipital lobe longitudinally rugose; remainder of head smooth and shining; promesonotal dome smooth and shining, sometimes with several rugulae dorsally; upper part of mesopleuron and lateral face of propodeum punctured largely; lower part of mesopleuron smooth and shining largely; lateral faces of petiole and postpetiole very weakly punctured; dorsa of petiole and postpetiole, and gaster smooth and shining. Outer face of mandible covered with appressed to decumbent hairs, which are 0.04-0.09 mm in length and as long as, or a little longer than, distance between piligerous punctures. Body light yellowish-brown, yellowish-brown or brown, with a little darker mandibles and clypeus (sometimes gaster is also darker than head and alitrunk); flagella and legs sometimes a little lighter than alitrunk.

Minor (n=9): TL 1.3-1.6 mm, HL 0.43-0.54 mm, HW 0.41-0.50 mm, SL 0.37-0.47 mm, AL 0.56-0.69 mm, FL 0.38-0.49 mm, CI 93-98, SI 88-97, FI 90-99. Head in full-face view almost straight or slightly concave posteriorly (Fig. 13D); occipital carina almost absent dorsally on head. Clypeus without a median longitudinal carina, with anterior margin in full-face view slightly convex or truncate medially. Eyes situated just in front of midlength of head; distance between mandibular insertion and anterior margin of eye 0.8-0.9 times as long as maximal diameter of eye. Frontal carina and antennal scrobe present only around antennal insertion. Antenna with 3-segmented club; scape slightly extending beyond posterior border of head; terminal segment 1.1-1.2 times as long as preceding two segments together. Promesonotal dome without a prominence on its posterior declivity (Fig. 13E). Mesopleuron without a distinct transverse impression. Dorsal outline of propodeum almost continuous and straight in profile (Fig. 13E); propodeal spine elongate-triangular, 3.5-4 times as long as diameter of propodeal spiracle. Petiole cuneiform, ca. 1.2 times as long as postpetiole (excluding helcium); petiolar node in posterior view not emarginate at apex. Postpetiole 1.8-2.2 times as broad as petiolar node.

Dorsolateral face of head slightly rugoso-reticulate; remainder of head including clypeus smooth and shining; promesonotum smooth and shining; mesopleuron and lateral face of propodeum punctured; lateral face of petiole very weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Body light yellowish-brown to yellowish-brown; antennae and legs a little lighter than alitrunk.

Type Material
Holotype Major, colony: Eg96-BOR-374, Gunong Rara (4°58'N 117°8'E, ca. 250 malt.), Sabah, E. Malaysia (Borneo), K. Eguchi leg., 1996, deposited in. Paratypes 8 majors, 12 minors and 5 queens 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., S. Yamane, and S.Y. Zho. 2007. Taxonomic revision of the Pheidole rinae Emery complex. Sociobiology 50 (1): 275-284.
 * 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.
 * 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.
 * 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.0040916
 * 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