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.
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.
Medius anterior: Vein MA is the anterior fork of the media, which is the “fourth” major longitudinal wing vein in insects. However, in mayfly forewings, the two forks often appear to be separate veins all the way to the wing base, and MA sometimes appears to branch from Rs near its base. Vein MA itself usually forks into an anterior fork MA1 and a posterior fork MA2. Usually, MA can be quickly located in mayfly forewings by looking for the vein that splits the wing in half length-wise and forks in two somewhere around 2/3 of the way from the base to the tip. MA and its forks are ridge veins (+).
These other words reference the same concept: media anterior, vein MA, MA vein, MA, vein MA1, MA1 vein, MA1, vein MA2, MA2 vein, MA2.
