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.
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
Subcosta: The subcosta (denoted Sc) is the second major longitudinal wing vein, located behind the costa, which it usually closely parallels along the leading edge of a mayfly’s forewing. It is a furrow vein (–).
These other words reference the same concept: subcosta, subcostal, subcostal vein, vein Sc, Sc, Sc.
