Wikipedia
Acanthostichus
Acanthostichus is a predatory and predominantly subterranean genus of ant in the subfamily Dorylinae. They are found in the New World, from the southern United States to Uruguay, Paraguay and northern Argentina. They are probably common, but due to their subterranean nature, they are seldom collected or seen.
Most species are very similar; the petiole is the most important feature in identifying species. Many are known only from a few collections, or even single specimen, which makes it hard to determine variability within species. For this reason, many described members of this genus may be synonyms.