Odontomachus infandus

Sorger, D. M. & Zettel, H., 2011, On the ants (Hymenoptera: Formicidae) of the Philippine Islands: V. The genus Odontomachus Latreille, 1804., Myrmecological News 14, pp. 141-163 : 148-149

The Odontomachus infandus species group

Diagnosis of worker: Large and slender species with long antennae and legs. Palp formula 4, 4. Head long, with distinct temporal prominences. Mandibles long, with long and sharp apical and subapical teeth. Mesosoma depressed. Pronotum with species-specific striation. Petiole high, without false peduncle anteriorly, with long apical spine.

Diversity and distribution: The group has a centre of speciation in the Philippines. At present we recognize Odontomachus banksi Forel, 1910 , O. infandus Smith, 1858 , and O. philippinus Emery, 1893 stat.n., three new species ( O. alius sp.n., O. schoedli sp.n., O. scifictus sp.n.), and two further undescribed species (O. sp. 1 and O. sp. 2) which remain unnamed. From New Guinea, three taxa are presently valid: Odontomachus animosus Smith, 1860 , O. latissimus Viehmeyer, 1914 , and O. papuanus Emery, 1887 . Mayr (1866) described one species from Fiji, O. angulatus Mayr, 1866 , and Brown (1976) described two species from the Lesser Sunda Islands east of Wallace's Line, O. sumbensis Brown, 1976 and O. floresensis Brown, 1976 . The group is also present on Sulawesi (undescribed material).

Notes: We exclude O. malignus Smith, 1859 from the O. infandus group based on a set of differences presented below (see O. malignus group). We also exclude O. silvestrii Wheeler, 1927 , from Vietnam and China, which was included by Brown (1976) based on mandible structures, as it differs greatly in many other characteristics, e.g., by short head and a densely punctured gaster.

Philippine species of this group differ from described taxa from other areas by an impression of the first gaster tergite in the worker caste at the point where the petiolar spine meets the gaster (Brown 1976: 125 suggests impression during pupation). This character is not developed in gynes. Moreover, at NHMW we have seen three specimens of an undescribed taxon from Sulawesi (Indonesia) with this same impression. Such an impression is also developed in O. saevissimus Smith, 1858 from the Moluccas to the Solomon Islands (in the O. saevissimus species group). In almost all Philippine worker specimens, the anterior slope of gaster tergite 1 is flattened (while it is rounded in species from other regions); an exception is the single worker of Odontomachus sp. 2 (unnamed) from Mindanao.

Description of workers from the Philippines: (Note: This description is provided to present characteristics that all Philippine species of this group have in common. These characters are not repeated in following species descriptions.)

Head in dorsal view broadly rectangular, longer than wide, broadest at level of eyes which do not surpass outline of head in frontal aspect. Temporal ridge shallow but present. Eyes situated dorsolaterally in anterior third of head. Head partly striate (except between eyes and antennal insertions, and posterior extension species-specific); in areas without striation, microsculpture smooth, with scattered, very fine punctures. Head dorsally with pair of long standing setae approximately at centre of head (occasionally broken off). Head venter with some long hairs (broken off in a few specimens). Clypeus with some fine short white hairs. Mandibles long, slightly shorter than head; ca. 12 teeth with peculiar dentition: teeth slightly increasing in size towards apex of mandible, but three apical teeth enlarged with intercalary tooth significantly (less than half) shorter than apical tooth and subapical tooth creating the "trap-jaw". Mandibles very finely striate laterally and dorsally, but smooth and shiny mesally and apically; with long trigger hairs located ventrally and directed forward.

Mesosoma slender, in dorsal view broadest at level of pronotum, all edges rounded. Pronotum roughly oval in dorsal aspect, with fine, species-specific striation. Mesonotum with transverse striation coarser than on pronotum. Propodeum with coarse transverse striation. Mesopleuron usually with fine transverse striation (reduced in some species). Mesosoma void of standing setae, except pronotum sometimes with two setae located approximately at centre (broken off in some specimens).

Metanotal spiracle large and situated near dorsal outline; propodeal spiracle situated laterally, approximately midway between dorsal and ventral outline of propodeum; metapleural gland orifice situated ventrolaterally.

Petiole long and acute, formed into an acute spine apically; in lateral view anterior face with an upward slope, petiolar spine bent backwards, posterior face of petiole usually S-shaped. Petiole usually smooth and shiny (except in O. banksi with some striation basolaterally).

Gaster rounded to oval in dorsal aspect, anterior face of tergite 1 usually flattened in lateral aspect (except in Odontomachus sp. 2 from Mindanao), and with a small impression; this impression usually pit-shaped, sometimes linear, sometimes weak (as individual variations without diagnostic importance). Gaster smooth and shiny, with dispersed fine hair pits. Gaster tergites 1 and 2 usually with out standing setae, or with few setae near posterior margin; following tergites with increasing numbers of setae.

Description of gynes: Although gynes are known only of four out of twelve species in this group, we assume that the following differences within worker morphs are applicable to all species of the O. infandus group.

Head structures similar to worker, but ocelli present, located medially in front of ocular ridge. Eyes slightly larger than in workers. Mesosoma strongly developed, high, bearing wings (or wing insertions). Pronotum transversely striate (striae curved). Mesonotum with coarse, parallel, longitudinal ridges, scutellum and metanotum smooth and shiny. Petiole slightly stouter than in workers, but of similar shape. Gaster large, tergite 1 without impression.