Philidris

Philidris is most common in forested areas where it is often associated with Myrmecophytes (especially the plant genera Myrmecodia and Dischidia). Unfortunately, the species within this genus have received little attention, either biologically or taxonomically.

Identification
Shattuck (1992) - Worker: Polymorphic (less commonly monomorphic), majors with ocelli; compound eyes placed relatively anterior on head; anterolateral clypeal margin posterior to the mediolateral region and separated from it by a shoulder; anteromedial clypeal margin with a central projection, either pointed or rounded (sometimes only feebly projecting); mandibles with 10 to 12 teeth, 0 to 3 denticles, and the basal angle weakly defined by a denticle. Extreme eastern India east through southeast Asia to the Philippine Islands, northern Australia and the Solomon Islands.

Queen: Anterolateral clypeal margin posterior to the mediolateral region and separated from it by a shoulder (sometimes weakly developed); anterior clypeal margin with about 20 short, erect setae; mandible with 7 to 10 teeth, 2 or 3 denticles, and the apical tooth subequal in length to the subapical; about 20 to 50 short, erect setae on mesoscutum; first gastral segment with a partial groove for the reception of the basal portion of the petiole. Male: Mandible with one tooth (the apical), about 10 to 12 denticles, and with the apical tooth subequal to or longer than the subapical tooth or denticle; venter of petiole with a well developed lobe; first gastral segment elongate posteriorly.

Philidris differs from Iridomyrmex in the placement of the compound eyes, the shape of the vertex, the prevalence of worker caste polymorphism, and the degree of anterior inclination of the petiolar scale. Additionally, workers of this genus tend to have a larger number of long, erect pronotal hairs compared to lridomyrmex species.

Distribution
Extreme eastern India east through southeast Asia to the Philippine Islands, northem Australia and the Solomon Islands.

Biology
These ants commonly nest in specialized ant plants. For example, [[Media:Peeters, C. & Wiwatwitaya, D. 2014. Philidris ants living inside Dischidia epiphytes from Thailand.pdf|Peeters and Wiwatwitaya (2014)]] document a fascinating ant-plant mutualism in SE Asia involving Philidris living in modified leaves of the epiphyte Dischidia major. These pitchers or domatia are easily defended and available for home improvements. A root grows inside the domatia to absorb nitrogenous wastes from the ants. Upon the slightest disturbance a large number of ants stream out with open mandibles, thus providing protection for host plants.

Ant presence was associated with both extensive root development and a variable quantity of debris. Pitchers offer a large empty space, much of which is unavailable to the ants and their brood unless they structure it. Philidris workers build internal partitions by using the roots as framework. Pitchers become spatially divided into many compartments, and close contact between roots and debris is appropriate for absorption, thus maximizing trophic benefits for the host plants.

The presence of inhabited Dischidia pitchers in the 30 m high crown of Dipterocarpus trees attests to the flying and searching ability of Philidris founding queens.

Peeters and Wiwatwitaya (2014) assumed that adjacent pitchers are all part of the same colony but did not investigate whether there can be other clusters belonging to the same colony on the same tree.



Castes
Queens are much bigger than workers, with large bulbous compound eyes comprising 300 – 350 ommatidia, compared with the smaller eyes of workers (50 – 60 ommatidia). Queens also have three prominent ocelli on top of the head. Thorax volume of queens is 28 times greater than that of workers (Peeters & Wiwatwitaya 2014). Queens are highly fecund with about 40 ovarioles. A maximum of six dealate, mated queens were collected together in the same pitcher.

Nomenclature

 *  PHILIDRIS [Dolichoderinae: Leptomyrmecini]
 * Philidris Shattuck, 1992a: 17. Type-species: Formica cordata, by original designation.

Worker
HEAD. Vertex concave. Compound eyes present, approximately round; relatively anterior on head. Ocelli present (in major). Antennae 12 segmented. Scape short, at most surpassing the vertex by less than one-third its length. Anterolateral clypeal margin posterior to the mediolateral region and separated from it by a shoulder. Anteromedial clypeal margin with a central projection, either pointed or rounded (often weakly developed). Anterior clypeal setae 4- 10; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Frontal carina present. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp segment at the apical extreme of segment 4. Mandible with 10-12 teeth and 0-3 denticles. Apical tooth slightly longer than the subapical tooth. Basal angle weakly defined by a denticle. Basal margin denticulate distally, smooth proximally. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Declivitous and dorsal faces of propodeum convex; dorsal face subequal in length to the declivitous face. Propodeal angle indistinct. Mesosomal spines and tooth absent. Erect pronotal hairs 8-24; elongate, much longer than the maximum scape width. Dorsal pro-mesonotal junction with the pronotum and mesonotum even, or with the mesonotum above the pronotum. Metanotal groove forming a distinct angle between the mesonotum and propodeum. Metanotal spiracle dorsal and lying on the dorsal surface when viewed in lateral profile. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). PETIOLE. Scale present; ridged and with a distinct angle dorsally; strongly inclined anteriorly and with the anterior face much shorter than the posterior face. Venter with a well developed lobe. GASTER. First tergite vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the basal portion of the petiole. Anteriortergosternal suture of the first segment extending laterally from the helcium in a distinct arch which extends dorsal ofthe dorsal helcial surface. Fifth tergite ventral, gaster with 4 apparent tergites. Gastral compression absent (gaster circular in cross section). Fourth stemite flat across entire posterior border. GENERAL CHARACTERS. Worker caste polymorphic or less commonly monomorphic. Chromosome number 8 (2n=16, P. cordatus, Imai et al. 1985a, Tjan et al. 1986). Integument thin and flexible, weakly sculptured. PROVENTRICULUS. Cupola much broader than bulb; round; with short pile; smooth, without sculpture; and with very broad phragma. Bulb completely hidden by cupola in lateral view. Occlusory tract absent.

Queen
HEAD. Vertex weakly concave. Compound eyes relatively anterior on head. Antennae 12 segmented. Scape short, surpassing the vertex by less than one- half scape length. Anterolateral clypeal margin posterior to the mediolateral region and separated from it by a shoulder. Anteromedial clypeal margin either entire (without a central notch or concavity of any type) or with a central projection, either pointed or rounded (sometimes only feebly projecting). Anterior clypeal setae 20; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin even with or posterior to the posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp segment at the apical extreme of segment 4. Mandible with 7- 10 teeth and 2-3 denticles. Apical tooth subequal in length to the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin denticulate distally, smooth proximally. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture varying from complete (but weakly developed anteriorly) to weak and nearly absent. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Axilla parallel and entire. Anterior axillar suture straight. Declivitous and dorsal faces of propodeum convex; dorsal face subequal in length to the declivitous face. Propodeal angle indistinct. Propodeal suture absent. Mesosomal spines and tooth absent. Erect mesoscutal hairs about 20-50; short, less than twice the maximum scape diameter. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). WINGS. Radial cell closed. Fore wing with 2 cubital and 1 discoidal cells. Hind wing with 2-3 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally; varying from moderately inclined anteriorly (but with the anterior and posterior faces approximately the same length) to strongly inclined anteriorly (and with the anterior face much shorter than the posterior face). Venter with a well developed, rounded lobe. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the basal portion of the petiole. Fifth tergite ventral, gaster with 4 apparent tergites. Gastral compression absent (gaster circular in cross section). Fourth sternite flat across entire posterior border.

Male
HEAD. Inner margin of eye entire, flat (or sometimes weakly angular). Scape length shorter than the length offunicular segments 2+3. First funicular segment barrel-shaped. Second funicular segment cylindrical, straight. Funicular segments 2 and 3 at most twice as long as broad. Third and fourth funicular segments straight. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 4; short, about as long as the maximum diameter of the scape; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. MOUTHPARTS. Palp formula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp at the apical extreme of segment 4. Mandible with one tooth (the apicaQ and about 10-12 very small denticles. Apical tooth (or denticle) subequal in length to, or slightly longer than, the subapical tooth. Basal angle indistinct, with a relatively uninterrupted curve between the two margins and without a distinct tooth or angle. Basal margin smooth and without teeth or denticles. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture present, complete. Anteromedial mesosternum even with the lateral regions. Axilla parallel and entire. Anterior axillar suture straight. Declivitous and dorsal faces of propodeum convex. Propodeal angle indistinct. WINGS. Radial cell closed. Fore wing with 1 cubital and 1 discoidal cell. Pterostigmal appendage absent. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally; vertical and not inclined anteriorly. Venter with a well developed lobe. Attachment to gaster broad. GASTER. First segment elongated posteriorly, smooth and without a groove or indentation. GENITALIA. Pygostyles present. Posterior margin of subgenital plate concave. Paramere divided by a weak membranous region. Digitus linear, with a slight ventral arch. Cuspis parallel with digitus. Ventral lobe of volsella present as concave lobe. Aedeagus with ventral teeth.

Larva
Protuberances present as 5 bosses located mid-dorsally. Body hairs sparse; simple; short.