Brachyponera

A moderately sized genus with more than 20 species, Brachyponera is unusual among ponerines in having a distinct size dimorphism between workers and queens, and in the invasiveness of some of its species.

Identification
Workers of Brachyponera can be differentiated from those of other ponerine genera by the following combination of characters: Mandibles usually with a basal pit (obsolete or vestigial in some species), eyes small and placed near the mandibular insertions, metanotal groove deep, propodeum at a lower elevation than the thorax and usually strongly narrowed dorsally, propodeal spiracle small and round, petiole squamiform, prora reduced and not externally visible, gaster with only a slight girdling constriction, and metatibiae with two spurs. None of these characters is autapomorphic within the Odontomachus group, but this combination of characters is unique. Brachyponera is most likely to be confused with species of Pseudoponera, but Pseudoponera lacks the mandibular pits, deep metanotal groove, and lowered propodeal elevation of Brachyponera. (Schmidt and Shattuck 2014)

Distribution
Brachyponera is widespread from Africa through southern Asia to Australia. It is most species-rich in Southeast Asia. Brachyponera chinensis was accidentally introduced to the southeastern United States and is now locally abundant (Nelder et al., 2006); it has also been introduced to New Zealand. (Schmidt and Shattuck 2014)

Biology
Brachyponera workers are among the smallest of the Odontomachus group, but like most members of the group are solitary epigeic generalist predators and scavengers. Nests are generally constructed in soil or rotten wood (Brachyponera chinensis: Ogata, 1987; Matsuura, 2002; Matsuura et al., 2002; Gotoh & Ito, 2008; Brachyponera croceicornis: Wilson, 1958c; Brachyponera lutea: Wheeler, 1933b; Haskins & Haskins, 1950; Brachyponera luteipes: Kikuchi et al., 2007; Brachyponera mesoponeroides: Radchenko, 1993; Brachyponera pilidorsalis: Yamane, 2007). Brachyponera is unusual among ponerines in that it displays a marked reproductive dimorphism between workers and queens, with the workers having completely lost their reproductive organs and queens having a large number of ovarioles (Ito & Ohkawara, 1994; Gotoh & Ito, 2008). Brachyponera also has the distinction of containing some of the only ponerine species considered to be pests: B. chinensis and B. sennaarensis, which are invasive and have potentially dangerous stings (see below).

Due to its pest ant status, Brachyponera chinensis has received more attention than most Brachyponera species. It seems to be fairly representative of the genus. B. chinensis is a generalist predator and scavenger, (Teranishi, 1929; Matsuura, 2002; Matsuura et al., 2002; Matsuura & Nishida, 2002), its nests are apparently polydomous (Gotoh & Ito, 2008), and its colonies average between 30 and 100 workers (Gotoh & Ito, 1998; Matsuura, 2002). Colony founding in B. chinensis is apparently semi-claustral (Koriba, 1963), and both monogynous and polygynous colonies have been observed (Gotoh & Ito, 1998). It is an invasive pest ant in the southeastern United States, having been accidentally introduced sometime before 1932 (Smith, 1934). The species is a public health concern due to the relative frequency of life-threatening anaphylaxis and other reactions to its venom (in Japan: Fukuzawa et al., 2002; in Korea: Cho et al., 2002; in the United States: Leath et al., 2006; Nelder et al., 2006).

Brachyponera sennaarensis is another invasive Brachyponera species. It is widespread in Sub-Saharan Africa and has recently been spreading northeastward through the Middle East (reaching as far as Iran), where it takes advantage of the relatively cooler and wetter climatic conditions provided by urban areas (Collingwood et al., 1999; Tirgari & Paknia, 2005; Paknia, 2006; Wetterer, 2012b). The species is very adaptable, occurring in both dry and humid habitats in its native range and having a very flexible diet (Déjean & Lachaud, 1994; L, 1994; Déjean et al., 1999). B. sennaarensis is a generalist omnivore but like many other Brachyponera species (and unusually for ponerines) will utilize seeds for food (Arnold, 1925; Lévieux & Diomande, 1978; Lévieux, 1979; Déjean & Lachaud, 1994; Lachaud & Déjean, 1994). Workers forage individually and will only recruit nestmates in times of general starvation (Lachaud & Déjean, 1994). B. sennaarensis is notable for the large size of its colonies (about 1,000 workers on average) and the striking size dimorphism between workers and queens (Déjean & Lachaud, 1994). Even more unusual is the presence of size polymorphism within the worker caste, which is rare among ponerines (Déjean & Lachaud, 1994). B. sennaarensis nests are constructed in soil and are multichambered, the chambers being connected by tunnels (Déjean & Lachaud, 1994). Tandem-running is used during emigrations to new nest sites (Lachaud & Déjean, 1994). Like B. chinensis, the sting of B. sennaarensis can cause life-threatening anaphylaxis (Dib et al., 1992). Longhurst et al. (1978) examined the mandibular gland secretions of B. sennaarensis.

The abundant and adaptable Australian species. Brachyponera lutea displays even more extreme size differences between the workers and queens than does B. sennaarensis (Wheeler, 1933b). The workers are tiny and hypogeic (unlike most Brachyponera). The large size of the queens enables claustral colony founding, though semiclaustral founding also occurs, as is the case with B. sennaarensis (Haskins & Haskins, 1950; Lachaud & Déjean, 1991b; Déjean & Lachaud, 1994). B. lutea has large colonies of over 2,000 workers, and is apparently largely predacious (Wheeler, 1933b; Haskins & Haskins, 1950).

Very little has been reported about other species of Brachyponera. Brachyponera luteipes is polygynous and may be polydomous or unicolonial, though the data on this are not conclusive (Takahashi et al., 2005; Kikucho et al., 2007). Interestingly, B. luteipes workers are aggressive toward queens of foreign colonies but not toward foreign workers (Kikucho et al., 2007). Like B. sennaarensis, B. luteipes is known to feed on seeds (Zhou et al., 2007). Wilson (1958c) reports that Brachyponera croceicornis is one of the most abundant and widespread ants in New Guinea, inhabiting a wide array of habitats; its colonies have about 100 workers.

Nomenclature

 * '' BRACHYPONERA [Ponerinae: Ponerini]
 * Brachyponera Emery, 1900c: 315 [as subgenus of Euponera]. Type-species: Euponera (Brachyponera) croceicornis, by monotypy.
 * [Brachyponera also described as new by Emery, 1901a: 43. Type-species not Ponera sennaarensis, unjustified subsequent designation by Emery, 1901a: 43, repeated in Wheeler, W.M. 1911f: 160, Emery, 1911d: 84, Wheeler, W.M. 1922a: 777, Donisthorpe, 1943g: 628, Wilson, 1958d: 346; Bolton, 1973a: 335 and Taylor & Brown, D.R. 1985: 23.]
 * Brachyponera as subgenus of Euponera: Emery, 1911d: 83; Wheeler, W.M. 1922a: 649.
 * Brachyponera raised to genus: Bingham, 1903: 101; Wilson, 1958d: 346.
 * Brachyponera junior synonym of Pachycondyla: Snelling, R.R. 1981: 389; Brown, in Bolton, 1994: 164.
 * Brachyponera revived from synonymy: Schmidt & Shattuck, 2014: 77.

Yamane (2007) - Brachyponera has the following recognition characteristics (W: worker, Q: queen, M: male): 1) Eye relatively large compared with those in Ponera and Hypoponera, located near the anterior margin of cranium (W/Q), 2) basal portion of mandible with shallow and elliptical fovea (but the fovea obsolete or absent in some species from Borneo, Bali, Krakatau and Sumatra) (W/Q), 3) mandible rather slender, boomerang shaped (M), 4) anterior margin of clypeus weakly and roundly produced, and medially shallowly emarginate (W/Q), 5) first funicular segment (pedicel) longer than second in W and Q, but much shorter than second in M, 6) palpal formula 3, 3 (W/Q), 7) mesonotum completely surrounded by suture/groove, i.e., promesonotal suture and metanotal groove deep and complete (W/Q), 8) mesopleuron with a transverse furrow always in Q and sometimes also in W, 9) propodeum compressed, seen from back narrowed dorsally (W/Q), 10) dorsum of propodeum distinctly lower than promesonotum (this condition also occurs in some Hypoponera species of similar size) (W/Q), 11) propodeum in profile demarcated from metanotum by a groove that passes near propodeal spiracle (rarely this groove is obsolete) (W/Q), 12) subpetiolar process with a backward-directed projection (Ogata described this projection as a pair of teeth for P. chinensis, but actually it is generally a single process, which is flat with a round apical margin, and in profile acute apically) (W/Q/M), 13) pygidium ending as a sharp spine posteriorly (M).

Schmidt and Shattuck (2014) - Worker Small to medium (TL 3–7 mm) ants with the standard characters of Ponerini. Mandibles triangular and usually with a small basal groove/pit. Frontal lobes small. Eyes small and placed far anterior near the mandibular insertions. Mesopleuron sometimes fully or partially divided by a shallow transverse groove. Metanotal groove deeply impressed. Propodeum at a lower elevation than the thorax, and usually strongly narrowed dorsally. Propodeal spiracle small and round. Metatibial spur formula (1s, 1p). Petiole squamiform. Girdling constriction between pre- and postsclerites of A4 apparent. Stridulitrum sometimes present on pretergite of A4. Head and body shiny to lightly punctate, sometimes with lateral striations on the mesosoma. Head and body with sparse pilosity and patchy pubescence. Color orange to black.

Queen Similar to worker but larger (sometimes much larger, as in Brachyponera lutea; Wheeler, 1933b), winged, with a wider and broader petiole, and with the other caste differences typical in ponerines. See description by Ogata (1987) for further details.