Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Radius: The radius (with its main branch denoted R1) is the third major longitudinal wing vein, located behind the subcosta. In mayfly forewings, it usually extends to a point near the wingtip. It is a ridge vein (+).
These other words reference the same concept: radial, first radial vein, vein R1, R1 vein, R1, vein R, R vein, R.
