Monday, April 9, 2012

Off to the Doyles: Lots of Spiny Crawlers -- But They Were Gorgeous!

I saw such colorful insects today, that it's hard to know where to begin.  But, this is the odd one -- kind of looks like the devil himself -- so let's put him ( or her) first.  The spiny crawler mayfly, Drunella walkeri.
This is only the second one that I've seen; the other was last year at Buck Mt. Creek.  Drunella nymphs are distinguished from Ephemerella nymphs, you may recall, by the "tubercles" (bumps) on the leading edges of the fore femorae.  These:

The key features that help us ID this as Drunella walkeri are -- and I'll quote from Steven Beaty ("The Ephemeroptera of North Carolina, p. 26) -- "body setose...genae produced into sharp anterolateral projections...abdomen with paired dorsal tubercles always well developed on segments 5-7."

The sharp, pointed genae are very clear to see on the live photos: they look like "horns"!

For the "setose" (i.e. hairy) body and the tubercles on segments 5-7, I'll have to use a microscope view (please click on it to enlarge).  The tubercles here are the sharp, pointed projections on the rear edges of segments 5-7.

Beaty points out that D. walkeri is typically collected in winter through spring.  Knopp and Cormier (Mayflies, p. 224), have it hatching in the East and Midwest from mid-July through early September as the "Eastern Blue-winged Olive."  This one sure was a beauty.

But the stream was loaded-- especially the leaf packs -- with the more common spiny crawler we find in the spring, Ephemerella, both E. dorothea and E. invaria.  And the E. invarias that I saw were more colorful than any spiny crawlers I've previously seen (other than the E. subvaria nymphs that I find in the Rapidan River).  Here's a couple of pix on the best one, one that was fairly mature (note the black wing pads).

Spectacular!  Just two more photos, these of the more "run-of-the-mill" spiny crawler nymphs in terms of color and pattern.  Still, fairly nice examples.   I was sure they were E. dorothea when I looked at them at the stream.  But I'm no longer sure one of the second: there seemed to be well-defined tubercles on the abdominal segments that would indicate E. invaria.  And Beaty (p. 27) points out that the E. invaria species " the most variable Ephemerella, in terms of size, color patterns, and size of tubercles."  Also, E. invaria tends to hatch before E. dorothea.


But the variety was rich at the Doyles River today, as the following photos confirm.

1. A beautiful, mature, Perlodid stonefly, Helopicus subvarians.  (I saw three or four.)

2. Another Acentrella turbida small minnow mayfly, which at first I thought might be A. nadineae. But that would require splashes of orange on the terga and thorax.  (Later note: I'm re-thinking this identification.  It is not A. turbida.  I'll post a clarification once I know for sure what it is. It may be some other species of Acentrella; it may also be genus Plauditus.)

3. A very yellow, immature, Epeorus pleuralis flatheaded mayfly.  So, there are still a lot of these around that haven't hatched.

4. And another freeliving caddisfly larva, Rhyacophila carolina.

Pretty wonderful time of year to be looking for insects in the streams of Virginia.

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