The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.
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.
