Metathorax

The metathorax is the third segment of the insect thorax, located behind the prothorax and mesothorax. Its dorsal sclerite is the metanotum, the ventral sclerite the metasternum, and the lateral pleural regions form the metapleura. The metathorax typically bears the hind pair of legs and, in many insects, the hind pair of wings.

Anatomically, the metathorax articulates anteriorly with the mesothorax and posteriorly with the first abdominal segment. Its musculature powers hind leg movement and, when wings are present, contributes to wing kinematics in coordination with the mesothorax. The segment often has a robust exoskeleton to support muscle attachments and mechanical loads during locomotion and flight.

In winged insects, the hind wings are attached to the metathorax, while the forewings attach to the mesothorax. In the order Diptera (true flies), hind wings are reduced to small balancing organs called halteres that arise from the metathorax and function in flight stabilization and sensing orientation.

Variation among insects includes species with reduced or absent hind wings, particularly in wingless or flightless lineages, where the metathorax may still be present as a functional segment for leg movement and attachment of muscles. The metathorax therefore plays a key role in both locomotion and, in many taxa, aerial locomotion.