The first
abdominal segment in
Apocrita Hymenoptera (
wasps,
bees and
ants) is known as the propodeum. 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 or not, and the presence or absence of such suture can aid in identifying specimens. == Mollusks ==