Photos from the Rapidan River: 12/15/13

Just a spectacular insect: the spiny crawler mayfly, Ephemerella subvaria, beloved by fly fishermen for providing the "Hendrickson" hatch.  The Rapidan remains the only place that I've found it, but then Beaty notes that it's "mountains only," and "rare."  (No tolerance value has been assigned.)

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I'll just post some photos today -- but I'll have more to say on this trip in a follow-up entry.  Why?  Because I found some Uenoids that I've not yet pinned down.  They could be Neophylax atlanta -- a species that's noted as "rare" -- but I need to look at them closely and study my sources.

Dark heads -- no yellow/red spots or stripes, no obvious "tubercle" on the heads, and they do have clavate ventral gills.  More later.
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The most common insect I saw today -- the pronggilled mayfly, genus Paraleptophlebia, but I didn't get any good photos!  So we move on ----

1. Large winter stonefly, Taeniopteryx burksi-maura.  This is the most mature nymph of the species I've seen so far this season.  Note the way the back wing pads flare out from the body.

2. Perlodid stonefly, Isoperla montana.  They're already showing their "stripes" (common name: "striped tails").

3. Giant stonefly, Pteronarcys proteus.  Lovely pattern on the pronotum and wing pads.

3. Lepidostomatidae (Scaly-mouth caddisfly), genus Lepidostoma.  There were a lot of them in the leaf packs.  I photographed two.

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And then there was this critter that didn't qualify as being "aquatic"!

Color at last: mature small winter stoneflies, Allocapnia pygmaea

Not exactly the morning I had in mind.  My destination was Buck Mt. Creek, but the water there was high and off-color.  True, we've had a lot of rain in the last 3-4 days -- still I was surprised. But I thought a small stream would be safe and headed to the Whippoorwill Branch of the Mechums.

This is a good stream for Uenoids -- and I found some -- but I saw a lot of small winter stoneflies in the leaf packs that were fairly mature, like the one in the photo above.  Another look.

Like most of the insects we see, the small winter stoneflies don't show off their colors until they reach these final stages.   Based on the work that I've done, I'd conclude that this is Allocapnia pygmaea, a very common small winter species.  For a detailed discussion of the features that lead us to this identification, look back to the posting of 11/4/12.  Here I'll just mention three points.  1) According to Harper & Hynes, A. pygmaea nymphs range from 6 -- 7.5 mm.  This nymph was 6 mm almost exactly.  2) Mature male A. pygmaeas have a long supraanal lobe, around twice the length of tergite 10.  And 3) On mature nymphs there is transverse banding on the abdominal terga.  Features 2 and 3 are both clear in the following photo.

We need the male nymph for exact identification, but I also found a female A. pygmaea today.  Note the difference in the supraanal lobe.  Also, the female abdomen -- and I've observed this before -- seems to be wider than that of the male.

We should see more and more mature small winter stoneflies through December and January and into February as well.
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But I was after Uenoids since I've never ID'd those that live in this stream to the level of species. The rocks were covered with Glossosomatids (Saddle case-makers), but I finally found some Uenoids.  I took photos of two, and both were Neophylax oligius, which, says Beaty, is the "most common Neophylax in NC."  (Beaty, "The Trichoptera of North Carolina," p. 87)

#1

#2

The faces give them away -- but let's review Beaty's description.  "N. oligius -- well developed clavate ventral gill on abdominal segment 1; yellow stripe on head, but varies, should be greater than 1/2 head length...underside of head usually testaceous."  (Beaty, p. 87)

The yellow stripes here are clearly greater than 1/2 the length of the head, and the undersides of the heads are indeed "testaceous" (reddish-brown or brownish-yellow).

For the "clavate ventral gills" we need a microscope view.  (clavate = narrow at the base and thick at the top: club-like)

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Finally a nice morning after a dark, dreary stretch.  Hope to get out again on Friday.  Might see more of these stoneflies.

Summary for 2013 and looking ahead to next year

While the year isn't over, it's been a little over three years since I started writing this blog.  So, I thought I would comment on this year's achievements.

A: Statistics.  I continue to find it surprising -- but satisfying -- that there are so many people in so many countries, that share my enthusiasm for this kind of study.   Here are the statistics on that as of this morning.

1. Total number of page views: 106,615
  Top 5 countries
     U.S., 67,293
     Canada, 3829
     U.K., 2928
     Russia, 2371
     France, 1713

2. Number of countries in which people are viewing the blog: 152

3. Months with largest number of page views: October, 2013; 6563: November, 2013: 6139
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B: Main focuses of the blog.  While I continue to try to record the first time each season that I see one of our regular taxa and continue to give "stream reports" on what I'm finding in local streams,  I find myself primarily focussing now on three different things.

1. I want to compile the most complete EPT list that I can for the streams in this part of Virginia.  I have no pretensions that my list will ever be exhaustive, but I'll keep working away on this project as long as my enthusiasm continues and I can still bend over!  The original EPT list was posted on 9/8/12, but I've continued to keep that list up-to-date.

2. I love finding new taxa -- and working out the ID.  It's the most exciting part of this hobby.

3. And I continue to try to get the best photos I possibly can of all of our taxa -- the regular and the new.
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C. Findings this year.  I have to admit that I'm partial to stoneflies -- the Perlodids in particular, especially the genus Isoperla.  And I found three new ones this year.

1. Isoperla davisi: Buck Mt. Creek

2. Isoperla orata:  Rapidan River

3. And Isoperla nr. orata:  Upper Doyles River, Rapidan River, and Buck Mt. Creek

The designation "Isoperla nr. orata" is my own -- nothing official about it.  Still, the resemblance to I. orata is clear, and they have strikingly similar laciniae.

I. orata

 I. nr. orata

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Other new taxa this year (not a complete list):

1. The common stonefly, Paragnetina fumosa (Buck Mt. Creek)

2. Common stonefly, Agnetina flavescens (Rapidan River)

3. Giant stonefly, Pteronarcys dorsata (North Fork of the Rivanna, Buck Mt. Creek, Rivanna -- main stem)

4. Flatheaded mayfly, Epeorus fragilis (South River, Greene County)

5. Small minnow mayfly, Labiobaetis propinquus (Rivanna River at Crofton)

6. Freeliving caddisfly larva, Rhyacophila fenestra/ledra (Doyles River, Lynch River)

7.  And the humpless casemaker just found by my friend in Sugar Hollow, Adicrophleps hitchcocki -- an "imperiled" insect in the state of Virginia

After three years, it's still a whole lot of fun.

The "other" small winter stonefly that we see in at least one of our streams: Paracapnia angulata

No, no -- that's not a small winter stonefly, but it's a nice photo to start off this entry.  The Perlodid stonefly Malirekus hastatus for which see the entry of 1/29/12 (full discussion of the ID).  The backs of the wing pads reveal that this nymph still has a long way to go before becoming mature (it was only 11 mm), but it lacks nothing in color and pattern.  Got some nice photos.

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Now on to the big story.   As you know, almost all of the small winter stoneflies we see in our streams are genus Allocapnia, mostly, I think, A. pygmaea and A. mystica.  They're common at this time of year, with a genus tolerance value of 3.3.  But I had found some "non" Allocapnia Capniids, Paracapnia angulata, in a small headwater stream in Sugar Hollow back in January, 2012.  Today my friend and I went back to that stream, and sure enough we found them again!

Yes I know, they're not much to look at: they were only 5 mm.  But they're real beauties when they mature.  Below, the two that I found on 1/30/12.

Since I just discussed how Paracapnia differ from Allocapnia nymphs (11/22/13), I won't belabor the point.  But the key thing is the shape of the wing pads: "meso- and metathoracic wing pads rounded" (Peckarsky, Freshwater Macroinvertebrates, p. 66).  I.e.

The wing pads are real hard to see on the nymphs that I found since they're so small -- but you can see them in these microscope views.

The "hairy" body -- clearly visible in these microscope photos -- is characteristic of the species (Stewart and Stark, pp. 141-144).  So too, I take it, is the oddly shaped abdomen -- bulbous? -- which swells dramatically from front to back on very young nymphs (see Donald Chandler's photo at http://www.discoverlife.org/mp/20q?search=Paracapnia+angulata).

Very cool.  This is one of the things I was hoping that we'd see today.  It's so nice when you find what you're after.  North carolina, by the way, does not assign a tolerance value to P. angulata.  That means they have not found enough samples.  Beaty does comment however: "Nymphs are collected late fall through mid-winter in the Mountains only," and "Nymphs typically occur in small headwater streams, possibly in leaf packs."  (Beaty, "The Plecoptera of North Carolina," p. 1)  That's where they were: I found them in leaf packs in a small headwater stream in the mountains (elevation, ~1200 FASL).

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We saw a lot of Peltoperlids (Roach-like stoneflies) today and a lot of common stoneflies -- Eccoptura xanthenses -- both of which are common in these small headwater streams.  And we found some flatheaded mayflies, M. merririvulanum and M. pudicum.  But I only photographed two other insects.

1. A Leuctrid -- rolled-winged stonefly -- the first I've seen so far this year, and I saw more than one.  Notice the long, thin abdomen.

2. And a spectacular Ameletid mayfly -- probably Ameletus cryptostimulus, but it's a little too early to call that for sure.

Oh.  I did find an Allocapnia small winter stonefly as well.  So they are found together.  Think this one is A. mystica.