Monday, January 3, 2011

North Fork of the Moormans: Return of the Epeorus!

The North Fork of the Moormans River flows out of the Shenandoah National Park directly west of Charlottesville.  It's a rough and tumbling mountain stream with lots of rocks and boulders and pools.  Hikers like walking along it, and in the summer, swimmers go there to cool off.  It's also a popular destination for fly fisherman.  In March and April, they can count on a good hatch of "Quill Gordons" -- scientific name Epeorus Pleuralis.

Epeorus Pleuralis is a "Flatheaded" mayfly -- family: Heptageniidae -- and the genus Epeorus is one of six Flatheaded genera we find in our streams.    It is not the most common, since it's only found in clean, cold, rocky, fast flowing water.  It's a genus I've only seen in the North Fork of the Moormans, the Moormans itself, Buck Mt. Creek, the Doyles River, and the Lynch River -- all streams that are not far from the Blue Ridge.  And I normally see them in large numbers from January through May.

Epeorus is the only Flatheaded genus that has only two tails: all the rest have three.  Also, the gills on this nymph are unique: they're large, fan out from the sides of the abdomen, and they look a lot like "suction cups".  They also function like suction cups!   All Flatheaded mayflies are "scrapers" in terms of their eating habits, so they need to cling to the rocks.  Living in fast-flowing streams, Epeorus nymphs use their large oval gills to help them accomplish this task.

The Epeorus nymphs that I found this morning were very small, some around 1/16 of an inch.  But they'll be growing to pretty good size by March; some will be as long as an inch.  In the pictures below, I've juxtaposed one of the small nymphs from this morning and a mature nymph from last season, then I show what the small nymph looks like magnified 45X.

I found very little else in the Moormans this morning: a few small winter stoneflies, some midge larvae,
some black fly colonies, a handful of Uenoid caddisflies, and one lonely Freeliving Caddisfly, an insect I'll say more about later on, but it too is a critter we only find in our very best mountain streams.

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