Saturday, April 20, 2013

Domination! E. dorothea (spiny crawler) and I. namata (Perlodid stonefly) take over our streams

The number of Ephemerella dorothea spiny crawlers in a lot of our streams at the moment is simply phenomenal -- thousands and thousands.  I was at the Doyles River this morning -- my lower site, just a mile from White Hall, VA -- and I couldn't pick up a leaf pack or a submerged bundle of twigs without seeing it "crawl" with life -- little spiny crawlers.  It's just that time of the year.  Oh you will see other things in the rivers, but they're few and far between in comparison with the spinys.

At the moment I'm seeing two different colors: orange -- like the nymph in the photo at the top of the page -- and brown.

But even the brown nymphs that I found this morning weren't the same hue.  I don't think this is a matter of gender -- but I don't know that for sure.  Another point, the orange nymphs always seem to be larger than the browns.  The male in the photo directly above was 6 mm; the orange nymph at the top of the page was closer to 8.

In terms of the stoneflies that are "dominating" a lot of our streams at the moment -- they're Isoperla namatas.  These:

They're not as numerous as the E. dorotheas, but they come in a close second.  They'll be hatching real soon as "Yellow Sallies" -- to the delight of fly fishermen!

(An important note on the name "Isoperla namata."  Steven Beaty has told me again that I shouldn't be using this name unless I live in the Ozarks or the midwest.  In "The Plecoptera of North Carolina," p. 24, he uses I. nr. namata for the insect in the photo above: more recently he told me they should be called I. kirchneri or I. montana.  I have to give this some thought.  I'm happy with I. montana since I. montana looks exactly like I. namata, and I. montana is attested for PA and WV.)

In any event -- those two insects, at the moment, are the main show in town, at least in our 2nd and 3rd order streams.  Next week I've got to get back to our small mountains streams (1st order streams) in Sugar Hollow and see what's going on there.

Other finds:

1. A small minnow mayfly, apparently Acentrella turbida -- though I've never seen one this color before.  Size: 4.5 mm.

2. And the small stonefly that is also common in at least some of our streams at the moment -- Nemouridae, genus Amphinemura.  March, April, May -- that's when we see them.

I've never seen a clean one (!), and I rarely get photos when they're fully intact.  Size: 5 mm.

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