Monday, March 28, 2011

Stream Report: Powells Creek near Crozet

I like to start with a "dramatic" photo whenever possible -- and this one's pretty dramatic.  I wish I had drawn back a little so the reader could see the length of its tails.  With the tails, this nymph was probably at least 1 1/2" long.  Flatheaded mayfly: genus Maccaffertium (formerly Stenonema).  This was the only "Mac" that I saw here today -- I did see a lot of flatheads that were genus Epeorus.

I urge the reader to look at my last report from the Powells: 2/14/11.  I had a microscope shot of some tiny Isoperla Perlodid stoneflies; I only found one or two.  Today, that was the "bug of the day".  I've never seen so many Isoperla Perlodids in one small part of a stream: they were all crawling around in the leaf packs.  A couple of photos: the colors and wingpads show these are already pretty advanced in their growth.

I also saw some Diploperla Perlodids: I had seen a number of them here in the winter, and I thought they might all be gone -- but not so.

When I had the nymphs in my dish for photos, the two different Perlodids lined up side-by-side.  The focus on the shot that I got isn't perfect -- but it's a rare chance to see how different Perlodid genera can be.

I only found one caddisfly -- a common netspinner, genus Hydropsyche -- but I managed a few good photos of it.  We expect this taxon and this genus to be dark green: not always the case.  A good look on the second shot of the netspinner's "anal claws," and the third shot gives us a great view of the "fuzzy belly" (Rose Brown) -- the tufts of gills on the abdomen.

I also found quite a few small spiny crawlers (all genus Ephemerella) -- too small to get any live shots.  But if you look at the post from 2/14, you'll see that then I found a REALLY small spiny crawler at Powells: at least today I could tell what these nymphs were without the use of my scope.

But, I had one very small insect that I had to bring home to ID.  It turned out to be my first Nemourid, genus Amphinemura, of the season!  We'll be seeing increasing numbers of these in our streams through April and May, and I can get some good live shots then.  This is the Nemourid with the frilly gills on both sides of its neck.  I've got a microscope shot that I took of this Nemourid -- but it's not very good.  Still, for what it's worth here it is.  This was probably 1/8" long.

If you look REAL close, you can make out the gills at the neck.

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