Well, my original ID was right! It's Maccaffertium pudicum

We learn by making mistakes: or so it sometimes seems.  After careful study of our flatheaded nymph from the Rapidan River -- and a little help from some friends (Steven Beaty, Jessica Fang) -- I find that my original entry was right.  This is Maccaffertium pudicum, Tolerance value -- as it should be for this river -- 2.1.

Here's what I discovered.

1) I remeasured the nymph: it is indeed 11 mm.  M. pudicum nymphs are 11-14 mm.

2) I was wrong about there being "denticles" on the protarsal claw.  What I had pointed to in the photo in my previous entry was a "basal tarsal claw," not a tooth.  There are no denticles on the protarsal claw of M. pudicum nymphs.

3) M. pudicum has posterolateral projections on segments 3-9.  Here's a better photo of that (I removed the gills on the right side), but I also see a projection on 2.  Also relevant to the ID, the projection on 9 is shorter than that on 8.  (See p. 33 in Bednarik and McCafferty.)

4) There are 30-40 lateral setae on the maxilla.  Tough to see all of them in my photo, but I count at least 31.  [For this data, see p. 14 in Philip A. Lewis, "Taxonomy and Ecology of Stenonema Mayflies,"  published by the National Environmental Research Center in November, 1974, in the Environmental Monitoring Series.  (Stenonema was changed to Maccaffertium for all but one species in 1979.]

5) While I can only see, using my microscope, 8 setae on the maxillary crown, pudicum should have 15-40.  I've already noted that there might well be more setae on the crown than I can see.

6) And the real key, for me, in establishing that this is a pudicum nymph, is that the ventral pattern is an exact match for one of the two patterns that we should see on pudicum nymphs: notice the splotches on 6-8, the largest/darkest being on 7, and the oblique anteromedial lines.

This illustration is found in Unzicker and Carlson's "Ephemeroptera," p. 3.75, figure 3.214.  Their essay is Chapter 3 in Aquatic Insects and Oligochaetes of North and South Carolina, edited by Brigham, Brigham, and Gnilka.  This illustration was originally published in A.F. Bednarik and W.P. McCafferty, "Biosystematic Revision of the Genus Stenonema", Canadian Bulletin of Fisheries and Aquatic Sciences, 201 (1979), p. 69, figure 78.  Their description (p. 33) reads as follows: "Sterna 4-8 mostly pale with brown markings varying from faint submedian dots and oblique dashes near anterior margins to median broad brown areas near anterior margins (fig. 78); 7 and 8 sometimes with brown maculation expanded to cover much of anterior parts of segments (fig. 79); 9 with brown lateral bands often connected or nearly so by brown cross band on anterior of sternum." (I've underlined a key phrase.)
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I've certainly spent more time on this nymph than I ever intended -- but I've learned a lot about the anatomy of mayflies.  Glad I was wrong in my last entry.  Oh, I should add that all sources say that M. pudicum nymphs hatch from April through September.  So this one was right on time!

Heading to Oregon on Thursday.  Very excited.  Get to see totally different stonefly, mayfly, and caddisfly species.
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It was NOT Maccaffertium pudicum: M. mediopunctatum? M. wudigeum?

Back to the drawing board on this one, this beautiful, fully mature flatheaded mayfly from the Rapidan River.    It was not Maccaffertium pudicum.  The problem is, using Beaty's "Ephemeroptera of North Carolina" (version 4), I can't really determine the ID for sure.  I'm hopeful that he'll take a look if I send the nymph to him in a vial.

Having looked carefully at all of the relevant features, I've arrived at two possibilities: M. mediopunctatum and M. wudigeum.  Let me show you how I got there.

1. The nymph, and it's fully mature, is 10 mm long -- tops.  Of the 15 species that Beaty describes, that feature alone eliminates all but the following:

M. exigum
M. ithaca
M. medipunctatum
M. meririvulanum
M. modestum
M. sinclari
M. terminatum
M. vicarium
M. wudigeum

 2. Another key feature in Mac ID is the presence or absence of denticles on the protarsal claw (claw on the first leg).  They are present on this nymph.  Two photos.

Of the species noted above, only 5 do have -- or "may" have -- those denticles.

M. exigum
M. mediopunctatum
M. modestum
M. terminatum
M. wudigeum

3. And another key feature -- the presence or absence of posterolateral projections on abdominal segments anterior to segment 6.  They are present on our nymph.

That leaves us with only two possible species ID's: M. mediopunctatum and M. wudigeum.
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Beaty's species descriptions read as follows.

M. mediopunctatum -- nymphs 7-10 mm; 0-9 (usually 5) hairs and 4-8 (usually 5-6) spine-like setae on maxillary crown; protarsal claws usually with denticles; posterolateral projections present anterior to segment 6; sternal maculations variable though usually with dark crossbands on sterna 2-8 and 9 with dark, obliquely oriented lateral bands, sometimes connected anteromedially.  A facultative summer species only found in the mountains, especially rivers.  (Beaty, p. 34)

     [Note: Beaty's earlier description of M. mediopunctatum (version 3.3) differs in one significant            way.  It ends: "sternal maculations variable though usually with dark crossbands on sterna 2-8,        and 9 with dark, inverted "U".   (p. 19)   I've put the key words in Bold.]

On the hairs and spines on the crown -- I can see 8 hairs and 5 spines.  (But the hairs are very difficult to see, and therefore to count.  There might be smaller hairs that I can't detect with my microscope.)

On the sternal maculations -- I could be convinced that there are "obliquely oriented lateral bands" on segments 1-9.  (Note the little red arrows.)

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M. wudigeum -- nymphs 8-10 mm (?); no hairs and 5 spine-like setae on maxillary crown; protarsal claws with denticles; posterolateral projections present on segments 3-9; dark coloration on outside edge of pronotum, clear on extreme lateral edge; abdomen mostly brown dorsally, each segment with pair of submedian dark dots; ventrally pale.  This recently described species will key to couplet 4 in Bednarik and McCafferty (1979).  Collected from upper Wilson Creek and the lower Linville River.  Listed by NC Natural Heritage Program as Significantly Rare (2012).  (Beaty, p. 35)

Probably not as good a fit as M. mediopunctatum.  Our nymph clearly has some hairs on the maxillary crown, and I'm not sure that the pronotum looks like it should (also not sure that it doesn't!).

However, it looks to me like the anterolateral projections do indeed extend from segments 3-9, and  there do seem to be paired submedian dark dots on at least some of the abdominal terga.

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Well, that's the best I can do.  Time to consult with the master.  I'm leaning towards M. mediopunctatum.  But, I'm bothered by the last line in Beaty's description: "A facultative summer species only found in the mountains, especially rivers."  It sure isn't summer, and this nymph is already fully mature.

Stay tuned.
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Photos from the Rapidan River: Beautiful insects, many mature

The water was high at the Rapidan River this morning, and I had to focus on rocks and leaf packs in close to shore.  But, I didn't have to work hard to find insects.  As I found the last time I was here, the leaf packs are crawling with Isoperla montana/whatever nymphs at the moment, but I saw tons of nymphs -- well, you know what I mean -- with large, tan wing pads, the color and form they assume before turning black.

I do not have new insects that I have to ID, so I'll focus on photos today, and we'll start with that beauty at the top of the page.

1.  Northern case-maker caddisfly larva, Pycnopsyche scabripennis.   First of the season.  This is a sizeable larva -- 20-25 mm --and the case is longer.  I've seen quite a few in the Rapidan River: every case is unique.

2. Perlodid stonefly, Isoperla nr. holochlora.   No change in the name.  It's still "close to" (nr.) Isoperla holochlora but not quite the same.  Not sure if Beaty is rearing this one this year, but I'm sure it's on his agenda.

3. Isoperla montana group.

a) with tan wing pads

b) darkening wing pads

c) dark wing pads angling away from the body.  (I assume this means that the nymph is in the process of hatching.  Need to check this with Beaty.)

4. Perlodid stonefly, Diploperla duplicata: 13mm.  Note that the wings are turning black on the edges.

5. Giant stonefly, Pteronarcys proteus: 33 mm.  Same comment: the wing pads are turning black on the edges.

6. And, a flatheaded mayfly, Maccaffertium pudicum.  Black wing pads, ready to hatch.

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Sometimes I wonder why I go anywhere else.

Identified at last! Well, sort of... One of our unknown Isoperlas

A torrential rainfall on Tuesday night has left almost all of our streams high, fast, and off-color.  So, I went to one of the smallest streams in Sugar Hollow that I could explore.  And I found one of the insects I was hoping to find.

This is a Perlodid stonefly, genus Isoperla, species unknown.   I've found it every year in the spring in at least three headwater streams in this valley.   Always in April and May.  This was the first -- discovered on 5/18/11.

I sent this nymph to Steven Beaty: he said it was one that he hadn't seen.   To his knowledge it had not yet been associated with an adult.  However, in a recent communication, he acknowledged that this nymph is now recognized from other parts of Virginia -- in the Blue Ridge -- and for the moment he's calling it "Isoperla sp. VA".  (Curiously, Beaty notes "collected only from SW Virginia along Skyline Drive and on WV and VA border. ???)   So, some progress.  It remains to have someone "rear" one of these  nymph and provide us with a name.  Not sure if that's on Beaty's agenda this year or not.

The distinguishing features are 1) the pale brown body color, and 2) the pattern we find on the head...which is this.

Those features might be easier seen on this nymph, found on 5/2/12.

One caveat -- it might look quite different when it's fully mature.  The following nymph was also found on 5/18/11.   The body color's exactly the same, but the head pattern is quite different.

In any event, the nymph that I found today was still very small.  I'll have to come back in May -- maybe late May this year -- to pick up nymphs that are closer to being mature.

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While I found a lot of insects today -- still lots of E. pleuralis flatheaded mayflies around -- I only photographed one other thing: the Ameletid mayfly, Ameletus cryptostimulus.

Very pretty.  And you know you're in a good stream when you find this particular species.

Tomorrow, off to the Rapidan River which I hope has dropped a little by now.

You have to dig in the substrate: the "common burrower" (Ephemeridae), Ephemera guttulata

It seems that we find at least one every spring: the common burrower, Ephemera guttulata, the "Eastern Green Drake" to fly fishermen.   Unfortunately -- for the fly fishermen who live around here -- the tiny streams where I find them are lacking in trout.

To repeat what we use for species ID:  "Genus Diagnosis: Mandibular tusks divergent apically and curved upward in lateral view; frontal process of head distinctly bifurcate; small gills on abdominal segment 1 forked; abdominal gills held dorsally; ventral apex of hind tibia produced into an acute point."  (Beaty, "The Ephemeroptera of North Carolina," p. 44)  And on the species ID: "nymphs up to 20 mm; abdomen generally lacking any color pattern.  Collected mostly during spring and summer.  Mountains only.  Uncommon.  Recorded from GSMNP."  In the photo below, we can see all of those features but the forked gills on segment 1.  This nymph was a young one: only 14 mm.

Love to find this one since it's so different from the other nymphs that we see.  But you only find them if you dig around in the sand and silt.

(For more on E. guttulata (hatch times, fly patterns to use), see Knopp and Cormier, Mayflies: An Angler's Study of Trout Water Ephemeroptera, pp. 105-109.)
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I was in Sugar Hollow this morning, and I started out at a very small stream at relatively high elevation, the one that I went to on 1/2/15 where I found the rare case-maker, Adricrophleps hitchcocki.  Today I didn't stay very long.  I was making my way upstream, the water clear and cold, when all of a sudden the water coming down from above turned muddy.  This is a steep incline and no one lives on the top of this mountain.  But something above me was walking around in that stream.  I was out of there!  This is bear country, and this is bear season.  And it's something I worry about when I'm up in the mountains at this time of year.
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So it was in another stream further downhill that I found our E. guttulata -- actually, right in this pool.

Lots of spiny crawlers (E. dorothea) now showing up in the leaf packs, but my focus was elsewhere.

1. The Perlodid stoneflies, Isoperla similis, were a dime a dozen.

2. So too were the northern case-makers, Pycnopsyche gentilis, having here abandoned their three-sided case of leaves.

3. And on the bottoms of rocks, lots and lots of flatheaded mayflies, Epeorus pleuralis, many of them now sporting black wing pads (i.e. they're ready to hatch).

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A good day -- just a great time of year to be out in the country in the state of Virginia.  (Below: entering Sugar Hollow.)

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UPDATE:  There is a more detailed description of E. guttulata in the latest version of "The Ephemeroptera of North Carolina" (Version 4.0, July 9, 2013).

guttulata -- nymphs up to 20 mm; frontal process long, notch deep, approximately half the length of the entire process; body brownish overall; both fore- and hind wing pads heavily blotched with irregular dark spots; abdomen broad, generally lacking any distinct color pattern, both dorsally and ventrally." (p. 84)

Remember that Beaty's keys/descriptions/documents are available online at: http://portal.ncdenr.org/web/wq/taxonmanual.