Costa

Definition

In insect wing morphology, the thickened anterior (leading) margin of the forewing and hindwing, formed by the first longitudinal vein (C) and the surrounding sclerotized cuticle. The costa extends from the wing base to the apex and serves as the primary structural support for the wing during flight; its shape, curvature, and the pattern of veins within the costal region (costal area or costal cell) are diagnostic characters in many insect orders, particularly Lepidoptera, Odonata, and Hymenoptera.

Etymology

From Latin costa ('rib, side'), referring to the rib-like anterior reinforcement of the wing.

Example

In dragonflies (Odonata), the costa forms a heavily sclerotized leading edge that helps prevent wing deformation during rapid aerial maneuvers, and the density of crossveins between the costa and subcosta varies systematically between families.

Synonyms

• costal margin
• costal vein
• C (vein notation)

Related Terms

• subcosta
• Radius
• cubitus
• anal vein
• pterostigma
• costal cell
• costal break
• venation

Usage Notes

In strict morphological usage, 'costa' refers specifically to vein C and its associated margin, while 'costal margin' or 'costal area' describes the broader anterior region of the wing containing multiple veins. The term is sometimes abbreviated as 'C' in wing-vein notation systems (Comstock–Needham and derivatives). Not to be confused with 'costa' as a surname or geographic term.