Pheidole hortensis

This species inhabits not only well-developed forests but also drier and shrubby vegetation. The species usually nests in rotting twigs and wood blocks on the ground, and stores up a number of tiny seeds in its nest (Eg96-BOR-062; Eg97-BOR-378, 448, 470). I have never encountered colonies containing more than one dealate queen. (Eguchi 2001)

Identification
Eguchi (2001) - P. hortensis is closely related to Pheidole maculifrons, Pheidole tenebricosa, Pheidole clypeocornis, Pheidole kikutai and Pheidole rugifera. All these are well recognisable among Indo-Chinese and Indo-Malayan congeners in having the following exceptional characteristics: masticatory margin of mandible bearing two denticles just in front of basal angle in the major (this condition is seen in only Pheidole fantasia except the above six species); ventral faces of midcoxa and hindcoxa distinctly reticulate (this condition is seen in only Pheidole aristotelis except the above six species). The following characteristics are also shared among the six species: frontal carina of the major horizontal, and (narrowly) overhanging antennal scrobe; hypostoma of the major bearing a median process. P. maculifrons is easily distinguished from the other five species collected from Borneo by having frons very weakly rugose longitudinally, vertex almost smooth and shining, dorsum of occipital lobe weakly reticulate, and alitrunk smooth and shining (one syntype major of P. maculifrons, labelled as “Holotype, MCZ, 22884”, was examined; close relationship between P. hortensis and P. maculifrons has already been suggested in Wheeler's original description). P. hortensis is distinguished from remainder of the five Bornean species as follows: in P. tenebricosa head and alitrunk of the minor punctured; in P. clypeocorniseach lateral part of clypeus of the major developed into a horn; in P. kikutai occipital carina of the minor complete; in P. rugifera head and alitrunk of the minor punctured, and outer face of mandible of the major with rugulae which run from its base toward masticatory margin.

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

Worker
Minor

Nomenclature

 *  hortensis. Pheidole hortensis Forel, 1913k: 38, fig. J (s.w.q.m.) INDONESIA (Java). Imai, Kubota, et al. 1985: 47 (k.). See also: Eguchi, 2001b: 61.

Type Material
Eguchi (2001) - Major, minor, queen and male. Type locality: Java. Nine syntypes (2 majors, 3 minors, 1 queen and 3 males) were examined.

Worker
Eguchi (2001) - Major (n=9): TL 1.8-2.6 mm, HL 0.87-1.15 mm, HW 0.77-1.05 mm, SL 0.38-0.48 mm, FL 0.46-0.62 mm, CI 85-95, SI 45-53, FI 55-63. Head broadest at about 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) (Fig. 20A), in profile weakly impressed on vertex (Fig. 20B). Hypostoma bearing a median process, which is sometimes much reduced compared with the process just mesal to each mandibular insertion (arrows in Fig. 20C). Clypeus without a median longitudinal carina, with anterior margin very weakly concave medially; each lateral part of clypeus weakly produced dorsally, but not well developed into a horn as seen in P. clypeocornis sp. nov. Eye situated at about 1/3 distance of head; distance between mandibular insertion and anterior margin of eye 1.5-1.8 times as long as maximal diameter of eye. Frontal carina horizontal, extending backward to about 3/5~2/3 distance of head (Fig. 20A). Antennal scrobe narrowly overhung by frontal carina. Antenna with 3-segmented club; antennal scape extending backward to ½-3/5 distance of head; terminal segment 1.1-1.3 times as long as preceding two segments together. Masticatory margin of mandible with apical and preapical teeth, and two denticles in front of basal angle. Promesonotum forming a high dome, without a distinct prominence on its posterior declivity (Fig. 20E); each dorsolateral portion of the dome roundly and strongly produced outward (Fig. 20D). Mesopleuron divided by a weak transverse impression into upper and lower parts. Propodeal spine triangular or elongate-triangular, 1.5-2 times as long as diameter of propodeal spiracle. Petiole 1.6-1.8 times as long as postpetiole (excluding helcium); petiolar node in posterior view not, or slightly, emarginate at apex. Postpetiole 1.5-1.8 times as broad as petiolar node.

Dorsum of head excluding occipital lobe longitudinally rugose, with interspaces smooth and shining (rarely punctured very weakly); dorsal and dorsolateral faces of occipital lobe reticulate, with enclosures smooth and shining (rarely punctured very weakly); outer face of mandible rugose only laterally near its base; dorsum of promesonotal dome smooth and shining with several transverse rugulae; upper part of mesopleuron weakly punctured; lower part of mesopleuron smooth and shining; propodeum smooth and shining, or weakly punctured in part; ventral faces of midcoxa and hindcoxa distinctly reticulate over the surface; lateral face of petiole slightly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Outer face of mandible sparsely covered with very short appressed hairs ( < 0.03 mm in length), which are (much) shorter than distance between piligerous punctures; submarginal zone of masticatory margin of mandible with a row of longer appressed hairs. Body yellowish-brown, reddish-brown or brown, with darker mandibles, clypeus and gaster (sometimes promesonotum also darker), or blackish-brown with lighter mandibles, waist and gaster; legs a little lighter than alitrunk.

Minor Measurements and indices (n=9): TL 1.3-1.7 mm, HL 0.41-0.50 mm, HW 0.39-0.48 mm, SL 0.35-0.47 mm, AL 0.52-0.65 mm, FL 0.36-0.48 mm, CI 93-97, SI 91-103, FI 92-101. Head in full-face view almost flat posteriorly (Fig. 20F); 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. Eye situated just in front of midlength of head; distance between mandibular insertion and anterior margin of eye 0.7-0.8 times as long as maximal diameter of eye. Frontal carina rarely present as an evanescent rugula extending beyond midlength of head. Antennal scrobe present only around antennal insertion. Antenna with 3-segmented club; scape extending beyond posterior border of head by its 1/5 length; terminal segment 1.1-1.2 times as long as preceding two segments together. Promesonotal dome without any prominence on its posterior declivity (Fig. 20G). Mesopleuron sometimes with an inconspicuous transverse impression. Propodeal spine ca. 1.5 times as long as diameter of propodeal spiracle. Petiole 1.5-1.6 times as long as postpetiole (excluding helcium); petiolar node in posterior view not emarginate at apex. Postpetiole ca. 1.7 times as broad as petiolar node.

Clypeus smooth and shining; remainder of head largely smooth and shining, or weakly rugosoreticulate between eye and antennal insertion; promesonotum smooth and shining; remainder of alitrunk punctured at least partly; lateral face of petiole weakly punctured; dorsum of petiole, and postpetiole and gaster smooth and shining. Body light yellowish-brown, yellowish-brown or light brown, sometimes with a little darker head and gaster.

References based on Global Ant Biodiversity Informatics

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 * Eguchi K. 2003. A study on the male genitalia of some Asian species of Pheidole (Hymenoptera, Formicidae, Myrmicinae). Sociobiology 41: 317-355.
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 * 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
 * Wheeler W. M. 1937. Additions to the ant-fauna of Krakatau and Verlaten Island. Treubia 16: 21-24.
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