Metathorax

Definition

The third and posterior segment of the insect thorax, bearing the hind legs and, in winged insects, typically the hindwings. The metathorax comprises the dorsal metanotum, ventral metasternum, and lateral metapleura. It is generally smaller and less conspicuous than the mesothorax, and may be modified or reduced—most extremely in Hymenoptera Apocrita, where the first abdominal segment fuses to it forming the propodeum.

Etymology

From Greek meta- (after, behind) + thorax (chest, breastplate).

Example

In Diptera, the metathoracic wings are reduced to small, knob-like halteres that function as gyroscopic organs during flight, while the functional wings arise from the mesothorax.

Related Terms

• Mesothorax
• prothorax
• Metanotum
• metasternum
• metapleuron
• propodeum
• Haltere
• Thorax
• tagma

Usage Notes

Distinguished from the mesothorax (middle, bearing forewings when present) and prothorax (anterior, never bearing wings). In many insects the metanotum is reduced relative to the mesonotum. The term applies strictly to insects; other arthropods with three thoracic segments use segmental terminology (e.g., pereonites in isopods) rather than the pro-/meso-/meta- system. Some authors restrict 'metathorax' to the segment proper, excluding the propodeum in fused Hymenoptera.