Geographic spread of the samsum or sword ant, Pachycondyla (Brachyponera) sennaarensis (Hymenoptera: Formicidae)

The samsum or sword ant, Pachycondyla (Brachyponera) sennaarensis (MAYR, 1862), is a widespread, conspicuous ant in the savannas and open forests of sub-Saharan Africa and the Middle East. This ant is also common in villages and cities, where it is well known for its powerful sting that sometimes leads to anaphylactic shock in humans and even death. Recent first reports of P. sennaarensis from subtropical parts (> 23.4° N) of the Arabian Peninsula and Iran have led many researchers to conclude that populations of this ant are expanding. To evaluate this possibility, I compiled and mapped specimen records of P. sennaarensis from > 300 sites. I documented the earliest known P. sennaarensis records for 40 countries, including several for which I found no previously published records: Bahrain, Chad, India, Liberia, Mozambique, and Zambia. In 1925, when most of the world's ant fauna was still poorly documented, P. sennaarensis had already been collected from widely shattered locales in 26 countries across tropical Africa and Arabia. In addition, there is a single isolated 1896 record of P. sennaarensis from an apparently temporary population in tropical India. All P. sennaarensis records from subtropical sites north of 23.4° N (in Bahrain, Kuwait, Iran, Oman, Qatar, the United Arab Emirates, and Saudi Arabia) are from after 1950, except one record from just outside the tropics (Muscat, Oman; 23.6° N). It is possible that P. sennaarensis populations have lived in these subtropical areas for a long time, but are only now being reported, perhaps due to a recent population increase of this species. In fact, although the earliest specimen record from Iran dates to 2001, older residents of southeastern Iran remember the sting of P. sennaarensis from their childhood. Still, it is possible that P. sennaarensis has really expanded its geographic range northeastward into new regions during the past few decades. If true, and if populations of P. sennaarensis continue to spread eastward from Iran, through subtropical southern Pakistan, they could soon become established in tropical India, where this species may be expected to thrive.