pleuron

Definition

The lateral sclerite of a body segment in insects and other arthropods, forming the side wall of the thorax or abdomen and typically bearing the leg bases and spiracles. In the insect thorax, each segment has a pair of pleura (singular pleuron) that articulate dorsally with the tergum and ventrally with the sternum; the pleuron may be subdivided into anterior episternum and posterior epimeron by the pleural suture. In arachnids, the term is applied more loosely to lateral areas of the prosoma or opisthosoma.

Etymology

Greek pleura, 'side, rib'

Example

In a grasshopper, the large pleuron of the metathorax forms the lateral wall of the thorax and provides attachment sites for the powerful jumping muscles that operate the hind leg.

Synonyms

• lateral sclerite

Related Terms

• Tergum
• sternum
• episternum
• epimeron
• pleural suture
• Coxa
• Spiracle
• Thorax
• Sclerite

Usage Notes

Pleuron refers specifically to the lateral plate; do not confuse with pleura (the thin membrane enclosing the lungs in vertebrates). In entomological usage, 'pleuron' is singular and 'pleura' plural, though some older texts use 'pleura' for both. The term is most precise for pterygote insects with well-sclerotized thoracic pleura; in soft-bodied larvae or many arachnids, lateral areas may lack clear sclerotization and the term is applied by positional analogy.