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.
Bulla: An expanded, often lighter-colored point in a wing vein, usually about half-way up the front edge of a mayfly wing, in the subcostal vein (the first major vein not on the edge) and often in several other longitudinal veins alternating in a line near the middle of the wing. A bulla is a weakly chitinized point that allows the wing to flex during the upward stroke in flight to reduce air resistance, while the stiffening during the downward stroke to provide more lift.
These other words reference the same concept: bullae, bullar.
Red boxes highlight four bullae in the central part of the wing of a Cinygma dimicki mayfly spinner, with the largest in the in the subcostal (Sc) and second radial (R2) veins.
