mesothorax

The mesothorax is the middle of the three thoracic segments in insects, located between the prothorax in front and the metathorax behind. Each thoracic segment bears a pair of legs, so the mesothorax carries the middle pair. In most winged insects, the forewings are attached to the mesothorax, while the hind wings originate from the metathorax; in beetles, the forewings are modified as hardened elytra that cover the hind wings and the abdomen.

Anatomy and function: The dorsal surface of the mesothorax bears the principal plates of the segment, including the scutum and the scutellum. The scutellum is a small triangular plate situated behind the bases of the forewings. The mesothorax houses the major flight musculature that powers the forewings, and it serves as the anchor for the wing bases and their venation patterns. The structure of the mesothorax also influences leg articulation and thoracic flexibility during locomotion.

Variation and significance: Across insect orders the mesothorax shows diversity corresponding to wing form and flight style. Some lineages retain functional forewings on the mesothorax, others have reduced or absent wings, and in beetles the forewings function as elytra. In anatomy and taxonomy, the mesothorax is a standard reference point for describing thoracic morphology, wing bases, and venation patterns.