The acidopore is a component of ant anatomy; a round orifice located on the abdomen encircled by hairs which typifies the subfamily Formicinae. Wikipedia

Anatomical feature of an ant Wikidata

A conical structure with a small terminal opening, at the posterior end of an ant’s gaster through which it sprays formic acid and associated hydrocarbons, collectively comprising the venom. This structure is unique to, but characteristic of all members of the ant subfamily Formicinae. Wiktionary