postpetiole

The postpetiole is a morphological feature of many ants, referring to the second abdominal segment located between the petiole and the gaster. In ants with a two-segment waist, the small first waist segment is the petiole, and the second waist segment is the postpetiole, with the gaster situated behind it. This arrangement is characteristic of the subfamily Myrmicinae, whereas ants in other subfamilies such as Formicinae and Dolichoderinae typically have a single waist node (the petiole) between the mesosoma and the gaster.

Anatomically, the postpetiole is a distinct, sometimes variable, segment that can appear as a rounded or elongated swelling between the petiole and the gaster. Its size and shape vary among species and genera, and in some ants it may be relatively conspicuous while in others it is more subtle or partially obscured by dorsal plates.

The functional significance of the postpetiole is not fully understood and likely varies among species. It provides another articulation point for the metasoma, potentially enabling greater flexibility in abdomen movement and positioning, which can influence gaster orientation during feeding, defense, or labor activities. The presence or absence and the specific morphology of the postpetiole are important taxonomic characters and are widely used in dichotomous keys to identify and differentiate genera and species within Myrmicinae.

See also: ant anatomy, petiole, myrmicinae taxonomy.