The propodeum, propodeon[1] [2] or propodium is the first abdominal segment in Apocrita Hymenoptera (wasps, bees and ants). It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is strongly constricted posteriorly to form the articulation of the petiole, and gives apocritans their distinctive shape. There may be a suture between the propodeum and the thorax, like in Symphyta[3] or not, and the presence or absence of such suture can aid in identifying specimens.
Propodium is the anterior (frontal) part of the foot of a mollusk.