Cuneus

Definition

In Hemiptera, a triangular or wedge-shaped region at the distal (apical) portion of the forewing, located between the embolium and the membrane and bounded proximally by a fracture line (the cuneal fracture). The cuneus is characteristic of many Heteroptera, particularly the family Miridae (plant bugs), and its presence, absence, or shape serves as a key diagnostic character for species identification. In mirids, the cuneus is typically well-developed and membranous, contrasting with the more coriaceous basal portion of the hemelytron.

Etymology

Latin cuneus, wedge

Example

In the mirid bug Lygus rugulipennis, the cuneus is distinctly triangular with a dark apical marking, whereas in some orthotyline mirids the cuneus is reduced or fused with the membrane, making it less conspicuous.

Related Terms

• hemelytron
• Corium
• Membrane
• embolium
• cuneal fracture
• Distal
• Heteroptera
• Miridae

Usage Notes

The cuneus is absent or poorly developed in many non-mirid heteropteran families (e.g., Pentatomidae, Coreidae) and is not a feature of Homoptera or other insect orders. Specialists distinguish the cuneus from the general membranous tip of the hemelytron by its specific triangular shape and the presence of the cuneal fracture; in keys, 'cuneus present/absent' is often a primary couplet for mirid subfamilies.