A pair of processes are often seen between the mid-leg coxae on the ventral side of the mesonotum. The dorsal aspect of the metathorax has fused to the propodeum and its distinction from the propodeum is almost impossible. A groove is often seen between the mesonotum and the propodeum on the dorsal side. This groove is the remnant of the metanotum and is called the metanotal groove. This is often used for classification.
Ants usually have a swollen area called the metapleural gland lateral and ventral to the thorax.
This gland has an opening at a point slightly dorsal to the hind-leg coxa. This organ is thought to excrete a fluid containing anti-fungal agents. This is one of the characteristics of ants. Some castes or species of ants have no such organ. The sternum in the metathorax has degenerated, like that in the mesothorax.