Brachyponera sennaarensis

Widely distributed throughout sub-Saharan Africa, where it inhabits savannas and open forests; it is also the most common member of the subfamily in southern Arabia. While it is regarded as native at least throughout Africa, it is also notably preferring man-impacted habitats, such as human settlements, rubbish dumps and waste ground. Thus it is in question whether the species is indigenous to the Socotra Archipelago. It is a general scavenger but will attack other insects and has a painful sting. Allergic reactions to the sting, sometimes severe, are a problem locally in Arabia (DIB 1992, RrzK et al. 1998), where it is called the "Samsun ant". Probably because of awareness of the painful sting, Socotri people refer to this ant by a specific denomination ("diftim"), as different to the word for ant ("nimihil"). (Collingwood et al. 2004)

Identification
Sharaf et al. (2017) - Worker. Large species (TL 5–6). Head broader than mesosoma, with convex sides and emarginated posterior margin; eyes relatively large; metanotal groove deeply impressed; petiole a high and thick node with a straight anterior surface and a convex posterior surface; first and second gastral tergites separated by a distinct constriction characteristic for ponerine ants; gaster ending with a powerful sting. Dark brown to blackish brown, antennae, tibiae and tarsi reddish. All body surfaces covered with fine and dense pubescence.

Distribution based on Regional Taxon Lists
Afrotropical Region: Burkina Faso, Cameroun, Chad, Eritrea, Guinea, Ivory Coast, Kenya, Mali, Namibia, Niger, Saudi Arabia, Senegal, Sierra Leone, Socotra Archipelago, Sudan, United Arab Emirates, Yemen, Zambia, Zimbabwe. Oriental Region: India. Palaearctic Region: Bahrain, Iran, Oman, Qatar.

Biology
This appears to be the only ponerine ant that can feed on seeds. Diet varies seasonally and geographically: in humid tropical regions of Africa, both seeds and insect prey are collected during the rainy season, whereas diet consists exclusively of seeds during the rainy season that lasts three months (Dejean & Lachaud 1994). In dry tropical regions however, foragers react to the absence of seeds in the rainy season by adopting a 100% animal diet (Lévieux 1979).

Morphology
Billen and Al-Khalifa (2015) - Abstract: The pro- and postpharyngeal glands of Brachyponera sennaarensis both appear as globular formations at a general anatomical level. However, only for the propharyngeal gland do these formations correspond with spherical secretory cells with diameters of 30-40 μm. For the lobed postpharyngeal gland, in contrast, this globular appearance is caused by the bulbous protrusions of the epithelial cells. This lobed appearance and globular cell shape also occur in the postpharyngeal glands of other Ponerinae and thus may represent a phylogenetic character. At the ultrastructural level, the propharyngeal gland cells are characterized by a well-developed granular endoplasmic reticulum, which is in agreement with its presumed production of digestive enzymes. The postpharyngeal gland cells contain a well-developed smooth endoplasmic reticulum, which allows the production of a nonproteinaceous secretion.

Billen and Al-Khalifa (2018) - As in other stinging ants, the venom gland of both queens and workers is formed by two free filaments in which the initial venom synthesis starts, a reservoir sac that encloses the convoluted gland portion, and the venom duct, that opens through the sting (Fig. 1). The paired filaments have a length of approx. 1.5-2 mm and a diameter between 40 and 50 μm, and are situated in between the other abdominal organs with a close proximity to the fat body (Fig. 2A). Both filaments fuse together to become a single unpaired filament shortly before entering the reservoir sac. The unpaired filament is considerably thinner than the paired filaments and has a diameter of 10-15 μm (Fig. 2B). Upon entering the reservoir sac, it expands to form the convoluted gland portion, which is entirely invaginated inside the reservoir sac (Fig. 2C, 4A). The reservoir sac is surrounded by a thick muscular supply (Fig. 2C), while also an occasional nerve can be observed (Fig. 2B). The elongated reservoir sac has a length of approx. 700 μm and a width around 400 μm, and has a cuticle-lined epithelial wall with a thickness of less than 1 μm (Fig. 2D). The venom duct has a length of approx. 750 μm and a diameter around 50 μm and enters the sting base dorsally to the Dufour gland duct, both ducts are associated with bundles of muscle fibres (Fig. 2E,F).

The venom gland filaments consist of class-3 secretory cells (classification of Noirot & Quennedey 1974) that are arranged around a central cuticle-lined filament lumen, into which they open through their accompanying duct cells (Fig. 3A). Each duct cell connects with a secretory cell through the end apparatus, which is formed by a cuticular continuation of the ductule that is surrounded by a sheath of microvilli (Fig. 3B). The cuticular characteristics in the duct cell and the end apparatus differ considerably: in the duct cell, the cuticular lining is thick and continuous, whereas in the end apparatus it is thin and discontinuous (Fig. 3B). The cytoplasm contains a well-developed Golgi apparatus and numerous mitochondria. Endoplasmic reticulum could not be observed, but numerous free ribosomes and polysomes give the cytoplasm a fine granulated appearance (Fig. 3C). In between the secretory cells of the free filaments, tracheoles (not shown) and nerve fibres can be observed (Fig. 3D).

The ovoid convoluted gland is completely internalized inside the reservoir sac, and measures approx. 400x200 μm. Careful tearing open of the reservoir sac of critical point dried material allows observation of the convoluted gland with scanning microscopy (Fig. 4A). Its external surface appears striated, with irregularly scattered small pores with a diameter around 0.5 μm (Fig. 4B). The internal reservoir wall, in contrast, shows a less dense striation without any pores (Fig. 4C). As a continuation of the venom gland filaments, the bulk of the convoluted gland is made up of secretory tissue with class-3 gland cells with a clear end apparatus and their accompanying ducts. The ducts open both along the continuation of the internal lumen inside the convoluted gland lumen and along the periphery of the convoluted gland (Fig. 1, 4D,E).

Oman
Sharaf et al (2018) - This species was found nesting under a stone and foraging on the ground. Several individuals were found in moist soil under a stone next to a date palm tree. In the KSA it has been observed inhabiting sites near human settlements and has an apparent preference of hot habitats (Sharaf & Aldawood, unpublished data)

Saudi Arabia
Al-Khalifa et al (2015) - Collingwood (1985) observed and reported B. sennaarensis in the Kingdom of Saudi Arabia, where it is commonly known as the samsum ant. Later, Collingwood and Agosti (1996) followed and recorded their occurrence in Oman, Yemen and Kuwait, whilst Collingwood et al. (1997) reported it in the United Arab Emirates. B. sennaarensis is considered to constitute a public health hazard in the Kingdom of Saudi Arabia owing to its sting, which has been known to cause cases of fatal anaphylactic shock (Dib et al., 1992, 1995). Al-Shahwan et al. (2006) reported a case of anaphylactic shock and since then several more such cases have been reported following samsum ant stings, some of which were really critical (Al-Anazi et al., 2009). Notwithstanding this negative reputation, however, B. sennaarensis can also be beneficial to humans: Dkhil et al. (2010) found that B. sennaarensis venom has an antiinflammatory effect that may be useful in the treatment of inflammatory skin diseases, whilst Badr et al. (2012) found that B. sennaarensis venom induces apoptosis in certain human breast cancer cells.

In this study, B. sennaarensis was detected in four provinces: ArRiyadh, Jazan, Najran and Eastern Province but was not detected in, Asir, Northern Frontiers, Tabouk, Makkah and Al-Madina. Collingwood (1985) suggested that the Arabian Peninsula is probably the northern limit of B. sennaarensis distribution. Different levels of occurrence of B. sennaarensis in the different regions of Saudi Arabia essentially confirm the non- indigenous status of the species. The population level also appears to depend on the geographical features of the location, with the high altitude of Asir, Makkah and Al-Madina regions, that each stands between 2000 and 3000 m above sea level, appearing to prohibit the occurrence of the species. Provinces such as Jazan and Najran are partially or completely Afrotropical in climate, since B. sennaarensis is indigenous to Africa this would explain their occurrence here. ArRiyadh and the Eastern region, meanwhile, are infested with a large number of ants due to large, frequent transport and heavy exchange of goods (Al-Khalifa et al., 2010). The Tabouk and Northern frontier regions, meanwhile, remain behind in terms of their developmental aspect and geosocial contacts, due to their distant location from the inhabited regions and have thus not yet been reached by these ants (Siddiqui and Al-Khalifa, 2013).

Yemen
Sharaf et al. (2017) - Brachyponera sennaarensis has invaded a wide range of habitats on Socotra, especially soil that is moist covered with the leaf litter of date palm trees. This species also commonly nests under rocks and objects associated with moist soils. Brachyponera sennaarensis has also invaded the relatively undisturbed valleys of the island where streams and denser vegetation are found. A nest was found under a stone under a dragon blood tree.

Nomenclature

 *  sennaarensis. Ponera sennaarensis Mayr, 1862: 721 (w.) SUDAN. Santschi, 1910c: 350 (q.); Forel, 1910c: 245 (m.); Wheeler, G.C. & Wheeler, J. 1971b: 1207 (l.). Combination in Euponera (Brachyponera): Emery, 1901a: 47; in Brachyponera: Wheeler, G.C. & Wheeler, J. 1971b: 1207; in Pachycondyla: Brown, in Bolton, 1995b: 309; in Brachyponera: Schmidt & Shattuck, 2014: 81. Senior synonym of sorghi: Wheeler, W.M. 1922a: 777; Menozzi, 1930b: 80. Current subspecies: nominal plus decolor, ruginota. See also: Arnold, 1915: 73.
 * sorghi. Ponera sorghi Roger, 1863a: 169 (w.) SUDAN. Combination in Euponera (Brachyponera): Emery, 1911d: 84. Junior synonym of sennaarensis: Wheeler, W.M. 1922a: 777.