Mesoponera

Mesoponera is a moderately sized genus, with more than 25 described species and subspecies. It is restricted to the Old World tropics from Sub-Saharan Africa to Australia and the Solomon Islands.

Identification
Schmidt and Shattuck (2014) - Mesoponera workers are perhaps the least derived of any ponerine genus, as they lack any obvious apomorphies. Mesoponera bears superficial resemblance to a number of other relatively plesiomorphic genera, especially Fisheropone, Neoponera, Mayaponera, Pseudoponera, and Hypoponera, and to a lesser degree genera such as Hagensia,Megaponera, and Paltothyreus. Mesoponera can be separated from these genera by the following combination of characters (most of which are probably plesiomorphic): mandibles without a basal groove, frontal lobes very small and closely approximated, eyes relatively small and placed anterior of head midline, preocular carinae absent, pronotum without sharp lateral margins, metanotal groove shallow to moderately deep (in Mesoponera subiridescens and Xiphopelta species), propodeum narrowed dorsally, metapleural gland orifice without a U-shaped posterior lip, metatibia with a large pectinate spur and a smaller simple spur, petiole surmounted by a simple scale which lacks sharp lateral margins, gaster with only a moderate constriction between A3 and A4, metatibiae with two spurs, arolia not prominent, and head and body only weakly sculptured with sparse pilosity but dense pubescence.

Distribution
Members of this genus are found throughout Sub-Saharan Africa (including Madagascar) extending to Yemen (Mesoponera flavopilosa) and the Seychelles (Mesoponera melanaria macra), with a second set of species occurring from Sri Lanka eastward to northern Australia and the Solomon Islands. (Schmidt and Shattuck 2014)

Biology
Almost nothing is known about the ecology or behavior of most Mesoponera species, especially members of the M. melanaria and M. subiridescens groups. Donisthorpe (1941) and Wilson (1958c) note that Mesoponera papuana nests in rotting wood and forages diurnally in leaf litter, and that Mesoponera manni nests in rotting wood or soil, but otherwise reports of their habits are scarce.

Most species in the M. ingesta group are similarly unstudied, but Mesoponera caffraria has received a fair bit of attention. This species is a predator of insects and also collects sugary liquids. It is locally abundant (Lévieux, 1983) and colonies are fairly small (roughly 60 to 120 workers; Agbogba, 1992, 1994). Nesting occurs in the ground (Villet, 1990b) or in active or abandoned termitaries (Agbogba, 1992; Déjean et al., 1996, 1997), and colony founding is semiclaustral (Villet, 1990b). Queens inhibit reproduction by workers, but orphaned workers lay fertile eggs (Villet & Duncan, 1992). The division of labor of M. caffraria workers has been well studied and is unusual. Rather than displaying a typical age-dependent polyethism, individual workers show a remarkable degree of task specialization, which is determined at an early age (Agbogba, 1992, 1994). Apparently only a low rate of role change occurs after this initial specialization (Bonavita & Poveda, 1970; Agbogba, 1992). Roughly two-thirds of workers specialize on intra-nest activities (studied by Agbogba, 1991), while the remainder specialize on foraging (Bonavita & Poveda, 1970). Foragers further specialize on the collection of sugary liquids or on either the stinging or retrieval of insect prey. When hunting termites, the behavior of M. caffraria foragers varies depending on the species and caste of the termites encountered (Agbogba, 1985). Interestingly, large groups of M. caffraria foragers will attack termite nests, and the entire ant colony will then emigrate into the nest, at least temporarily (Agbogba, 1990, 1992). Both the recruitment of foragers and the movement of the colony are coordinated through tandem running, using both visual and chemical cues (Agbogba, 1984 and 1992). Masson (1970a, 1970b, 1972) studied the neuroanatomy and neurodevelopment of M. caffraria, Bonavita & Lemasne (1970) studied food exchange between M. caffraria workers, and Bonavita & Poveda (1972) examined intestinal structure in M. caffraria larvae.

Nomenclature

 *  MESOPONERA  [Ponerinae: Ponerini]
 * Mesoponera Emery, 1900d: 668 [as subgenus of Euponera]. Type-species: Ponera melanaria, by monotypy.
 * [Mesoponera also described as new by Emery, 1901a: 43. Type-species not Ponera caffraria, unjustified subsequent designation by Emery, 1901a: 43, repeated by Emery, 1911d: 81, Wheeler, W.M. 1911f: 167, Wheeler, W.M. 1922a: 775, Donisthorpe, 1943g: 661, Wilson, 1958d: 349; Kempf, 1972a: 141, Bolton, 1973a: 338 and Taylor & Brown, D.R. 1985: 35.]
 * Mesoponera raised to genus: Bingham, 1903: 99; Wilson, 1958d: 349; Schmidt & Shattuck, 2014: 107.
 * Mesoponera subgenus of Euponera: Wheeler, W.M. 1910g: 135; Emery, 1911d: 80; Wheeler, W.M. 1922a: 649; Borgmeier, 1923: 71.
 * Mesoponera senior synonym of Xiphopelta: Wheeler, W.M. 1922a: 775; Schmidt & Shattuck, 2014: 107.
 * Mesoponera junior synonym of Pachycondyla: Snelling, R.R. 1981: 389; Hölldobler & Wilson, 1990: 11; Brown, in Bolton, 1994: 164.
 * Mesoponera revived from synonymy: Schmidt & Shattuck, 2014: 107.
 * XIPHOPELTA [junior synonym of Mesoponera]
 * Xiphopelta Forel, 1913a: 108 [as subgenus of Ponera]. Type-species: Ponera (Xiphopelta) arnoldi, by monotypy.
 * Xiphopelta subgenus of Euponera: Forel, 1917: 237; Bernard, 1953b: 191.
 * Xiphopelta junior synonym of Pachycondyla: Snelling, R.R. 1981: 389; Hölldobler & Wilson, 1990: 11; Brown, in Bolton, 1994: 164.
 * Xiphopelta junior synonym of Mesoponera: Wheeler, W.M. 1922a: 775; Schmidt & Shattuck, 2014: 107.
 * [Hiphopelta: incorrect subsequent spelling by Forel, 1913a: 108.]

Schmidt and Shattuck (2014):

Worker
Medium (TL 5–9.5 mm) slender ants with the standard characters of Ponerini. Mandibles triangular, relatively long; mandibles crossed when closed in the M. melanaria group. Eyes small, placed anterior of head midline; absent or reduced to a small pigmented spot in a few species. Frontal lobes very small and closely approximated. Mesopleuron usually not divided by a transverse groove. Metanotal groove shallow to moderately deep (in Xiphopelta species). Propodeum narrowed dorsally. Propodeal spiracles small and round in most M. melanaria group species, but slit-like in the M. ingesta group. Metatibial spur formula (1s, 1p). Petiole squamiform. Gaster with only a weak girdling constriction between pre- and postsclerites of A4. Stridulitrum sometimes present on pretergite of A4. Head and body finely punctate, with sparse pilosity but a dense fine pubescence. Color variable. (Note: This description excludes M. subiridescens, which we place within Mesoponera only tentatively. M. subiridescens differs from the above description by its shining cuticle, relatively large eyes, mesopleuron divided by a transverse groove, deep metanotal groove, and long narrow toothless mandibles which have distinct basal grooves and basal margins that are not concealed by the clypeus when closed.)

Queen
Similar to worker, but winged and with the other differences typical for alate ponerine queens.

Male
See descriptions in Arnold (1915) and Donisthorpe (1942).

Larva
Described by Wheeler & Wheeler (1971b).