Metapone

Introduction
The genus Metapone Forel remains one of the most unusual and enigmatic ant genera in the Old World. Most of the 17 described taxa are known from very few specimens, often single queens or males are collected during dispersal flights and occasionally workers are collected from dead wood. Forel (1911) established the genus Metapone based upon a series of workers, larvae and reproductive pupae of the type species M. greeni Forel, collected from Peradenyia, Sri Lanka. In the same paper, Forel designated Metapone as the type genus of a new tribe Metaponini and provisionally placed this tribe into a new special section among the Ponerinae, which he called the Promyrmicinae.

The genus Metapone was properly transferred to the subfamily Myrmicinae a year later by Emery (1912) when he realized that the larvae were characteristic of the Myrmicinae and not the Ponerinae. Unfortunately, Emery misinterpreted certain ponerine-like morphological traits of Metapone as primitive rather than as derived adaptations to a highly specialized habit of foraging in galleries of wood. As a result, Emery retained Forel’s section Promyrmicinae, transferred it to the Myrmicinae, and expanded it to include the tribes Metaponini and Pseudomyrmicini. Wheeler (1919) was able to clear up much of the earlier confusion after additional species of Metapone became available for study. Wheeler rejected the term Promyrmicinae even though he could not determine the position of the Metaponini among the other tribes within the Myrmicinae. The genera Metapone, Liomyrmex, Vollenhovia and Xenomyrmex were included until recently in the tribe Metaponini (Bolton, 1994, 1995). Metapone is presently the only genus assigned to the tribe Metaponini (Bolton, 2003). The placement of the Metaponini within the Myrmicinae remains problematic and awaits a comprehensive revision of the myrmicine tribes. The genus Metapone is widely distributed throughout the Indo-Australian, Oriental and Malagasy Regions (Taylor, 1991; Bolton, 1995; Eguchi, 1998; Alpert, 2007). Even though specimens are rare, new species continue to be discovered. Eguchi (1998) described a new species from Borneo, an undescribed Metapone has been found in Gabon (B. Bolton, B. Fisher, personal communication) and another undescribed Metapone has been found recently in New Caledonia (C. Burwell, personal communication) and in the Philippines (Gary Alpert, personal communication). There are several series of undescribed Metapone from Papua New Guinea and Australia in the Australian National Insect Collection in Canberra, Australia

Character States
Metapone Worker/Queen Antennal Count = 11 segments with a 3-segmented club. Palp Formula: 2 maxillary palp segments and 3 labial palp segments. Total Dental Count = 4-5 teeth on the masticatory margin. Spur Formula = 1 pectinate spur on the mesotibia and 1 pectinate spur on the metatibia.

Male = Antennal Count = 12 segmented antennae with no club. Palp Formula = 2 maxillary palp segments and 2 labial palp segments. Total Dental Count = 3-5 teeth on the masticatory margin. Spur Formula = 1 pectinate spur on the mesotibia and 1 pectinate spur on the metatibia.

Metapone has the following derived characters (Bolton 2003): •Procoxae smaller than meso- and metacoxae •Metafemur highly anteroposteriorly compressed, extremely deep in anterior view •Apex of mesotibia, metatibia and basitarsi of all legs with traction spines •Presclerites of abdominal segment IV very large •Articulation of abdominal segments III and IV very broad

Biology
From the very first collections, Metapone workers have been found in association with termites. The type species of the genus, Metapone greeni, was found in “galleries in a decayed branch, which was also infested by two species of termites” (Forel, 1911, quoting E.E. Green, the collector). Subsequently, Wheeler (1919, 1936) listed M. greeni as an inquiline of termites and suggested that all species of Metapone probably form small colonies and live in or near the galleries of termites in dead wood. Taylor (1991) has found several undescribed species of Metapone in association with termites in Australia. In Papua New Guinea, Metapone were found in rotten wood with termites of the genus Prorhinotermes (Leigh Miller, personal communication). Eguchi (1998) reported that Metapone quadridentata Eguchi from Borneo “was collected from the galleries of a termite nest in rotten wood”. Gregg (1958) obtained from Alfred E. Emerson, the noted termite specialist, two new species of Metapone (Metapone emersoni and Metapone madagascarica) from a series of termites collected from Madagascar by Harold Kirby in 1935. Additional specimens of M. madagascarica were collected in association with Coptotermes truncatus Wasmann and Cryptotermes sp. (Brian Fisher, written communication). Though the evidence is anecdotal, the pattern of obligatory association with termites is clear.

Castes
Metapone madagascarica is a highly unusual species in having both normal winged males and worker-like ergatoid males without wings. Both forms have been found together in the same nest. Other species of Metapone are known to have queens and intermediates between queens and workers.

Nomenclature
METAPONE [Myrmicinae: Metaponini] Metapone Forel, 1911h: 447. Type-species: Metapone greeni by monotypy.

Additional References

 * ] [Alpert, G. D. 2007. A review of the ant genus Metapone Forel from Madagascar, pp. 8-18. In Snelling, R. R., B. L. Fisher, and P. S. Ward (eds). Advances in ant systematics (Hymenoptera: Formicidae): homage to E. O. Wilson – 50 years of contributions. Memoirs of the American Entomological Institute, 80.