Pheidole schoedli

This species is considered a subterranean ant because (1) the specimens were found in soil samples but not in the litter samples; (2) eyes are extremely reduced and body color is yellowish. Thus, this species and P. parvicorpus, which is also presumably subterranean, are ecologically unique among Bornean Pheidole species.

Identification
This species is well distinguished from other Oriental species of the genus in having a combination of the characteristics given in the diagnosis. However, when referring to EGUCHI (2001), the present species may be identified to Pheidole parvicorpus EGUCHI, 2001 of which worker is also characterized in having extremely reduced eyes. The two species are undoubtedly closely related to each other, but they are well distinguished as follows: 1) The scape almost reaches or a little exceeds the posterior margin of the head in the minor of Pheidole schoedli sp.n., but does not reach the posterior margin of the head in the minor of P. parvicorpus. 2) The hairs on the head and the first gastral tergite are clearly categorized into two types in the major of P. schoedli sp.n. (short decumbent/appressed hairs and long standing hairs), but not in the major of P. parvicorpus (hairs are subdecumbent to suberect and similar in length). 3) The basal segment of the club is longer than broad in the worker of P. schoedli sp.n., but as long as or shorter than broad in the worker of r P. parvicorpus; 4) The eye consists of at most 4 ommatidia in the minor of P. schoedli sp.n., but 5 or 6 ommatidia in the minor of P. parvicorpus. Cranium (excluding median part of clypeus) entirely covered with decumbent / appressed hairs among which standing hairs are scattered [major]; eye much reduced, consisting of at most 10 ommatidia [major] and at most 4 ommatidia [minor]; frontal carina and antennal scrobe absent [major]; antennal segment X longer than broad [major and minor]; hypostoma with a pair of long submedian processes, but without median process [major]; promesonotal dome without conspicuous prominence on its posterior declivity [major and minor]; postpetiole not massive [major and minor].
 * Diagnosis.

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

Biology
Annette Malsch collected the type series of Pheidole schoedli sp.n. from the top soil (820 - 860 m a.s.l.) during nest sampling on the ground. She finds neither workers nor colonies of the species from her Winkler samples, while Y. Hashimoto extracted the workers and dealate queens from his soil-core samples. BRÜHL & al. (1998), using Winkler litter sifters, extensively extracted litter-dwelling ants between 550 and 1140 m a.s.l. in Poring Hot Spring (the type locality) but did not obtain any specimens of P. schoedli (K. Eguchi examined his samples: see http:// www.antbase.de/literature-pdf/ants-of-poring-2005.pdf). These field observations as well as morphological features including much-reduced eyes and yellowish body in the worker caste suggest that this species is a subterranean nester and forager. The worker of Pheidole parvicorpus also has much-reduced eyes and yellowish body. Nests of P. parvicorpus have been found in soil-core samples as well as in rotting wood on the ground (see EGUCHI 2001), but we have never examined P. parvicorpus collected by baiting and pit-fall trapping on the ground. Thus, P. parvicorpus may be also a subterranean forager and occasionally or usually a subterranean nester. We frequently encounter Pheidole species foraging actively on the ground surface (EGUCHI & al. 2004), while WILSON (2005) obtained evidence that at least three small-sized Neotropical species of Pheidole most frequently prey on oribatid mites which are one of the most abundant small invertebrates of the soil and litter. Thus, it is important to study food preference and foraging ecology of Pheidole parvicorpus and P. schoedli in order to understand functions of Pheidole species, dominant ants in tropical and warm temperate ecosystems.

Castes

 * Major Worker

Nomenclature

 *  schoedli. Pheidole schoedli Eguchi, Hashimoto & Malsch, 2006: 32, figs. 1  7 (s.w.m.) BORNEO.

Description
Holotype: major from Sample No. 4186; type locality: Poring Hot Spring, East ridge, 820 - 860 m a.s.l., Sabah, Malaysia (leg. Annette K.F. Malsch, 16.V. 1998); depository: ITBC. Paratypes: 10 majors, 24 minors and 1 male from the same colony to which the holotype belongs, depository: NHMW, ITBC, BMNH, MHNG, MCZ, MNHA, ACEG. Malaysia: Sabah: Maliau Basin [Y. Hashimoto's soil core: 1-1, 2-12]; Deramakot Forest Reserve (secondary Forest) [leg. C. Brühl]. Measurements and indices [n = 5]: HL 1.85 - 2.04 (1.97) mm; HW 1.54 - 1.71 (1.63) mm; SL 0.81 - 0.92 (0.87) mm; FL 1.05 - 1.27 (1.19) mm; CI 82 - 84 (83); SI 53 - 55 (54); FI 68 - 76 (73). Body yellowish brown. Head in full-face view elongate, relatively shallowly concave posteriorly; vertex in profile not impressed (in the type series), or often very weakly impressed (in non-type specimens from Maliau Basin); cranium except median part of clypeus covered with short decumbent/appressed hairs; long standing hairs scattered among the decumbent/appressed hairs; frons smooth, but sparsely sculptured with short interrupted longitudinal rugulae (type series), or weakly rugose longitudinally with interspaces weakly punctured (specimens from Maliau Basin); vertex almost smooth (type series, see Fig. 3), or weakly rugose-reticulate longitudinally with interspaces weakly punctured (specimens from Maliau Basin, see Fig. 4); dorsal and dorsolateral faces of vertexal lobe almost smooth (type series, see Fig. 3), or weakly rugose-reticulate (specimens from Maliau Basin, see Fig. 4); anterolateral face of dorsum of head reticulate; gena longitudinally rugose; median part of clypeus smooth, without median longitudinal carina; frontal carina and antennal scrobe absent; hypostoma with pair of well-developed lateral processes (just mesal to each mandibular base) and pair of long submedian processes (arrows in Fig. 5), but without median process; outer surface of mandible entirely smooth and shining except its base, scattering decumbent/appressed hairs; antenna 12-segmented; scape a little exceeding midlength of head when it laid backward; antennal club 3- segmented; basal segment of club (antennal segment X) longer than broad; eye much reduced, consisting of at most 10 ommatidia. Promesonotal dome weakly punctured anterodorsally, smooth or dimly rugose-punctate dorsally, smooth on central part of lateral face; dome in profile without conspicuous prominence on posterior declivity; humerus very weakly produced (dome at humeri almost as broad as at bottom); mesopleuron, metapleuron, and propodeum weakly punctured (in the type series central part of mesopleuron and anterolateral part of propodeum smooth); propodeal pine elongate triangular. Petiole much longer than postpetiole (excluding helcium); petiolar node low, in rear view at most very weakly concave mediodorsally; postpetiole not massive. First gastral tergite sparsely pilose with short decumbent/appressed hairs and long standing hairs, weakly to dimly rugose-punctate at least around its articulation with postpetiole. Measurements and indices [n = 6]: HL 0.83 - 0.89 (0.86) mm; HW 0.78 - 0.82 (0.80) mm; SL 0.68 - 0.74 (0.71) mm; FL 0.72 - 0.82 (0.77) mm; CI 91 - 94 (92); SI 86 - 91 (89); FI 92 - 100 (97). Body pale yellow. Head in full-face view weakly concave posteromedially; frons and vertex smooth and shining (posteriormost part of vertex dimly rugose in specimens from Maliau Basin); dorsolateral part of head and gena very weakly rugose-punctate; dorsal part of preoccipital carina obsolete; median part of clypeus smooth and shining, without median longitudinal carina; antenna 12-segmented; scape almost reaching or a little exceeding posterior margin of head; antennal club 3-segmented; basal segment of club longer than broad; eye much reduced, consisting of at most 4 ommatidia. Promesonotal dome in profile relatively low, without conspicuous prominence on posterior declivity; dorsum of dome smooth and shining, but with anteriormost part (type series, specimen from Deramakot) or anterior slope (specimens from Maliau Basin) weakly punctured; lateral face of dome largely smooth (partly very weakly punctured); humerus in dorsolateral view not or hardly produced; mesopleuron weakly punctured, often with smooth central part; metapleuron weakly punctured or almost smooth; propodeum (except smooth anterolateral part) weakly punctured; propodeal spine small, elongate-triangular. Petiole longer than postpetiole (excluding helcium); petiolar node low, in rear view hardly concave or not concave mediodorsally; postpetiole not massive, weakly punctured posterodorsally and laterally.
 * Type material.
 * Non-type material examined.
 * Major
 * Minor

References based on Global Ant Biodiversity Informatics

 * Eguchi K.; Hashimoto Y.; Malsch A. K. F. 2006. Pheidole schoedli sp.n. (Hymenoptera: Formicidae), a subterranean species found from North Borneo. Myrmecologische Nachrichten 8: 31-34.
 * Hashimoto Y., and M. Mohamed. 2011. Ground-dwelling ant diversity in Maliau Basin, Borneo: evaluation of hand-sorting methods to estimate ant diversity. Tropics 19(2): 85-92.
 * 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