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.
One of the most important things to a choosy trout is the one thing my close-up pictures can't show: motion. Fly tyers imitate motion by using lively materials, and fly anglers imitate it with subtle rod-work, but both need to understand how the real critters move. Most of these were shot long ago with an ancient digital camera.
In angling books, Leptophlebia mayfly nymphs have a reputation as poor swimmers. In reality, they're very adept swimmers, much moreso than most other mayfly nymphs categorized as "crawlers."
This is one of the earliest videos I made, and I was experimenting with a tank and background that didn't work very well.
Water boatmen are excellent swimmers, and you can see here how they use their oars to push themselves through the water, a motion easily imitated by the fly fisher.
The clumsy-looking mayfly nymphs of the genus Baetisca are surprisingly good swimmers.