It’s stonefly season in the West—the big, adult bugs will be popping on a river near you before you know it.

And, while the dry-fly imitations are easily the most popular—and the most fun to fish—it’s the nymph patterns that likely catch more trout. And there are some great stonefly nymph patterns out there. But perhaps the best stonefly nymph imitation doesn’t even go by the name “stonefly.”

It’s the Girdle Bug, and it’s a killer in rivers with good stonefly populations, particularly in late spring and early summer when the nymphs are working their way to the banks in anticipation of the big hatch.

The Girdle Bug looks like an easy tie, but, honestly, it takes some practice. Above, Matt Callies of Loon Outdoors ties a great version of the fly and notes that it does require some dexterity to get it right. As is usual with most fly patterns, practice makes perfect.

The Girdle Bug can be tied just as Matt ties it in the short video above, or it can be tied with added weight—don’t hesitate to give it a bead head or use lead-free wire to give it some sink.

It’s a great fly to fish near streamside rocks in the weeks and says prior to the actual stonefly hatch, or as a dropper under a big stonefly dry imitation. Don’t fish a classic freestone river without a handful in the box.