Tyrannomyrmex

In 2003, Fernández described a new genus and species, Tyrannomyrmex rex from peninsular Malaysia based on a single specimen collected from leaf litter at Negri Sembilan, Pasoh Forest Reserve in 1994 (Fernández, 2003). Since then, a second species, Tyrannomyrmex dux has been described based on a single specimen collected from leaf litter in southern India in 1999 (Borowiec, 2007). A third species, Tyrannomyrmex legatus was recently collected from leaf litter in Sri Lanka (Alpert, 2011). In addition, Brian Heterick recognized a single male collected from a light trap in the Philippines in 1965 as possibly representing an unknown male of Tyrannomyrmex.

Identification
Fernández (2003) -Tyrannomyrmex possesses a unique combination of traits which separate it from other myrmicines: modified setae along the internal border of the mandibles and mandibles with two teeth, apical and subapical, with the rest of the masticatory border lacking teeth. The modified setae are reminiscent of some of the Adelomyrmex, but in Tyrannomyrmex the setae are thick, nonspatulate, and cylindric. The antennal club is not easily-defined. At first glance it appears to be 2-segmented, but the last segments under careful examination might also be interpreted as 3-segmented.

Borewiec (2007) described the species Tyrannomyrmex dux, finding it had regular and not modified setae along the internal border of the mandibles.

Distribution
Known from Malaysia, India and Sri Lanka.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Workers are found in leaf litter. Other than locality information, the biology of these rare ants is unknown. Jacquemin et al. (2015) suggest, albeit based on a acknowledged paucity of collections, that the genus appears to be restricted to pristine or relatively undisturbed forests and, as a result, could be highly sensitive to habitat degradation.

Morphology
Jacquemin et al. (2015) - As previously noted (Fernández, 2003; Borowiec, 2007), the genus seems to lack a functional metapleural gland, a structure unique to ants and playing a key role in sanitation and chemical defense (Yek & Mueller, 2011). This gland has been secondarily lost is some ant lineages, mostly in social parasites and arboreal formicines, probably because their life histories render them less exposed to pathogens than ground-dwelling species (Yek & Mueller, 2011 and references therein). Its absence in Tyrannomyrmex, a probable hypogean genus, suggests either that these ants could be social parasites or that they possess other protections against pathogens as observed for instance in some Camponotus (Walker & Hughes, 2011) and Polyrhachis species (Graystock & Hughes, 2011). Additional material and anatomical studies are obviously required to test these hypotheses.

Nomenclature

 *  TYRANNOMYRMEX [incertae sedis in Myrmicinae]
 * Tyrannomyrmex Fernández, 2003a: 2. Type-species: Tyrannomyrmex rex, by original designation.

Worker

 * Mandibles with two teeth in the masticatory border, apical and smaller subapical. No teeth onin the basal margin of the mandible.
 * Inner ventral margin of masticatory border of mandibles with setae. Setae can be normal or modified.
 * Clypeus devoid of carinae.   Foveolae may be present.
 * Palpal formula 2, 2.   Confirmed.
 * Compound eyes small, reduced to a few ommatidia.
 * Antennae 11-segmented with an ill-defined 3-segmented club.
 * Frontal carinae and antennal scrobes absent.
 * Mesosoma without grooves.
 * Propodeal lobes large and round.
 * Sting large and robust.