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.
Medius posterior: Vein MP is the posterior fork of the media, which is the “fourth” major longitudinal wing vein in insects. However, in mayflies, the two forks often appear to be separate veins all the way to the wing base. Vein MP itself sometimes forks into an anterior fork MP1 and a posterior fork MP2, although MP2 sometimes only indirectly connects to MP via a crossvein. MP and its forks are furrow veins (–).
These other words reference the same concept: media posterior, vein MP, MP vein, MP, vein MP1, MP1 vein, MP1, vein MP2, MP2 vein, MP2.