Nemourid stonefly, genus Soyedina: here's where things stand

This is the stonefly nymph that I found in Sugar Hollow two weeks ago (March 9): family, Nemouridae; genus, Soyedina; species, initially undetermined.  You will recall that I was intrigued by what appeared to me to be paired tubercles on the posterior edges of terga 1-7.  These.

Steven Beaty was also intrigued and asked me to find more nymphs and/or adults if I could.  As luck would have it, I returned to that very small stream on March 12 and found an adult. I failed in my attempts to get a live photo of that adult, but here's what it looked like when it was preserved in a vial.

I wasn't sure that this was Soyedina, but when I checked the wing veination with sources, that ID was confirmed.   I sent both the nymph and the adult to Beaty.  He determined, first of all, that those "tubercles" were in fact tufts of setae that look bigger than they are due to detritus.  And on the adult, he feels that it's most likely S. carolinensis though the match apparently isn't exact.

Before I go any further let me add this.  At the moment, only two species of Soyedina are attested in the state of Virginia -- S. carolinensis and S. vallicularia. (Stewart and Stark, Nymphs of North American Stonefly Genera, p. 217) North Carolina has a total of four: S. carolinensis, S. kondratieffi, S. washingtoni, and a new, unnamed species -- n.sp. (Beaty, "The Plecoptera of North Carolina," p. 17)  The nymphs for the two species that are found in Virginia have both been described: carolinensis by Claasen in 1923 and vallicularia by Harper and Hynes in 1970.

So, is our stonefly S. carolinensis?  Beaty's best guess so far, but this conclusion is not unproblematic.  Why?  Because Claasen's description of carolinensis makes no mention of "tufts of setae" on the tergites, surely a feature he'd note.  I might add that such tufts are also unmentioned in the description of vallicularia.

We have to leave it at that though there are two other items worth noting.  1) On Bugguide.net, Tom Murray has posted a photo of a nymph that he ID's as S. washingtoni (http://bugguide.net/node/view/260938/bgpage), and, it too has those tufts of hair on the terga.  And 2) there is also a photo of S. vallicularia on which those tufts of setae are present as well (http://www.shl.uiowa.edu/env/limnology/plecoptera.xml)

Lots of uncertainty here in the association of nymphs with adults.  A lot more work needs to be done. Ah, but that's what Ph.D. dissertations are for!
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Here's the place where I found both the nymph and the adult.

Maccaffertium meririvulanum and Maccaffertium pudicum: how we tell them apart

We continue to look for Soyedina Nemourids: so far no luck.   The nymph that I found on 3/9 is one that's as yet "undescribed": it's either a new species of Soyedina or, what's more likely, one that has not yet been associated with an adult.  Steve Beaty wants us to send down more specimens -- so the search will go on.

In the meantime, I've been back to Sugar Hollow a number of times where we're finding numerous insects, including this spectacular flatheaded mayfly, Maccaffertium meririvulanum.  As we've noted before, M. meririvulanum and M. pudicum co-occur in pristine, headwater streams.  They're both fairly big nymphs (meririvulanum, 10-16 mm; pudicum, 11-14 mm) and look a lot alike -- but we can tell them apart.

While the ventral pattern is crucial for identifying almost all of the the Macs, the dorsal view suffices with meririvulanum.  The "V's" give it away.  Reading from Beaty ("The Ephemeroptera of North Carolina, p. 34): "...terga 5 and either 7-8, or 7-9 each with distinct V-shaped pale mark."  On our nymph they're easy to see on terga 5, 7, and 8.

In his descripton he adds: "ventrally pale."  True.

M. meririvulanum is one of the least tolerant species in the genus: TV of 0.5.
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To identify M. pudicum, it's best to go right to the venter, though I do find the orange/pale pattern on segment 7 to be a fairly consistent indication of species.

The venter can have 1 of 2 patterns.  On this nymph this is the venter we see.

Here is how Beaty describes this: "ventrally variable with anterior edges of sterna 3, 4, or 5-9 with irregular transverse markings, reduced on anterior segments on some specimens to medial blotches or oblique dashes and with sternum 9 with anteromedial markings extended to form an inverted "U"." ("Ephemeroptera," p. 35)  The "U" on 9 is obvious.  I'd say the oblique dashes and medial blotches are present on 3-6 (2 as well?), while on 7 and 8 these darken into transverse "moustache" like lines.
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Some of the other things we've been seeing.

1) Perlodid stonefly,  Isoperla similis/pseudosimilis Groups (a young one)

2) Leuctridae (Rolled-wing stonefly), genus Leuctra

3) and a very pretty Northern Case-maker, Pycnopsyche gentilis.

Some very nice photos today -- and a little surprise

The search is on for more Soyedina nymphs and some adults (see previous entry), something I'll explain in subsequent entries.  Suffice it to say that the nymph I noted last time is possibly one that's important, but we need more information.  Anyway, I didn't find any today, but I fared well nonetheless.

1. Above -- one of the better photos I've taken of the small minnow mayfly, Baetis tricaudatus.  I saw some small ones today but as you can see, this one was fully mature.  It remains the only small minnow mayfly I've seen in these tiny streams in Sugar Hollow, and with a TV of 1.5, it's where it belongs.  Some more photos.

2. And I found a couple of flatheaded mayflies, Maccaffertium pudicum, which also like these very small streams.

3. No surprises so far -- but this one was.

A pair of Isoperla, Perlodid stoneflies, and when I was taking my photos I was sure they were the very same species: Isoperla kirchneri group, possibly Isoperla kirchneri.   When I uploaded the photos, I saw that I was wrong.  Here they are again.

The first nymph in both sets is indeed I. kirchneri group, but the second is I. holochlora.  Can you see how they differ? Two things: 1) note the different abdominal patterns, and 2) look at the heads.  On I. kirchneri, the lateral stripes on the abdomen are straight, and the pale spot in the ocellar triangle is open to the rear.

But on I. holochlora, the inside edges of the lateral stripes are curved/scalloped and the pale spot on the head is completely enclosed.

I. kirchneri group nymphs are fairly common in these small mountain streams: not so with I. holochlora.  While I often find these nymphs at the Rapidan River, this is only the second time I've found them in Sugar Hollow.
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Back to Sugar Hollow tomorrow to explore something new -- need to find more Soyedina.

Oh.   And a fairly mature Chloroperlid (Green Stonefly), genus Sweltsa.

The Nemourid we find in our small mountain streams: genus Soyedina

As you can see this nymph was fully mature -- black wing pads -- and I guess I should have brought it home and tried my hand at rearing it.  That's the only way to determine the species.

Nemourid stonefly, genus Soyedina.  Let me read you Beaty's description.  "Nymphs 6.5-8.5 mm.  Pronotum with angulate corners and a distinct sublateral notch; pronotum with well-developed lateral fringe of short, closely set, thick setae; wing pads divergent; legs short, stout."  ("The Plecoptera of North Carolina," p. 17)

This nymph was 8 mm long.  You can see from our photo that the legs are short and stout.  For the pronotum features -- all clear in this microscope photo.

The species is undetermined, but I guess that's true for almost all of the Soyedina that we're liable to find in our streams.   There appear to be five different options: vallicularia, carolinensis, kondratieffi, washingtoni, and n. sp.  (a new species, unnamed).  That's why I should have given rearing a try.  Have to see if I can find another next week.  Location?  One of our small headwater streams in Sugar Hollow.  We've found them there before.  I collected this one in December, 2013.

There is something quite distinctive about this nymph that may help with nymph descriptions: there are evenly spaced postero-lateral tubercles on terga 1-7.

I'm sending this one down to Beaty for further review.  I'll let you know if he has any insights.  Soyedina nymphs are "relatively rare."

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The other insect I collected this morning was a tiny Uenoid -- Neophylax aniqua.

This is the Uenoid we find at high elevations.  The distinguishing features are: 1) a semi-blunt tubercle on the head; 2) 1-3 setae at the ventral sa3 position; and 3) absence of clavate gills.

You can actually see the tubercle in one of my live shots.

But it's much clearer in this microscope view, a view that also reveals 2 setae at sa3.

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Pretty good morning.  Lots of insects in our streams at the moment.

Apparently, Prostoia completa

Steve Beaty feels the Nemourids that I've been finding are most likely Prostoia completa.  He does not feel the presence or absence of intercalary setae on the caudal filaments is a reliable character in distinguishing similis from completa.  This is something he had already noted in his key ("The Plecoptera of North Carolina," p. 16): "Speciation between the three regional species [of Prostoia] hinges on the development of the intercalary setae on the cerci which has yet to be proven reliable." 

More reliable, apparently, is the length and density of the silky setae on the tibiae: on completa they're long and dense (well developed), on similis short and sparse.   He has sent me illustrations on the tibiae of both species that will be published in a forthcoming key developed by Stewart and Stark.  The tibiae of P. completa look exactly like those on the nymphs that I've been finding.  E.g.

In Beaty's 2015 key, he adds on P. completa: "This is a common species in the east and possibly in North Carolina.  It occurs in small streams to large rivers (Kondratieff and Kirchner, 1984a).  

So there you have it.  Now we know what they are.

Some nice pics of Ameletus sp.: a look at the Moormans

This morning, I went with my friend who lives in Sugar Hollow to the Moormans river, right down from her house.  We were curious to see if there were any Nemourids in there that we could check to the level of species.  There were.  But first things first.

One of the things that I found when I searched through the leafpacks was this Ameletid mayfly.   I think I've been identifying this one as A. cryptostimulus: I'm embarrassed to say I was wrong.  I re-read Beaty's description of A. cryptostimulus, looking for the dorsal features that he had listed -- just not there.  Two examples.  1) Note that the tarsi on our nymph are banded both apically and basally,

those on cryptostimulus have only an apical band.  2) Beaty describes the cryptostimulus cerci in the following way: "caudal filaments basally brown and with a dark brown medial band."  Those on our nymph are not basally brown.

In fact, these cerci match those of A. lineatus and A. ludens: "caudal filaments with dark median band interrupted every four segments by very narrow pale bands."  ("The Ephemeroptera of North Carolina," Version 4.0, p. 1)

Our nymph is, in fact, either lineatus or ludens.  Note Beaty's description of the terga of lineatus (ludens is much the same): "segments 1-8 with dark comma-like submedian markings."  Bingo.

So is it lineatus or ludens?  Well lineatus is bigger than ludens (12-14 mm, females  vs. 9.5? mm), and this was a pretty big nymph.  But there are other features -- especially on the sterna -- that have to be checked and I didn't keep the nymph!  Alas, next time.

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We did find some Nemourids.

The "face" on this one looked a little bit different than those I was finding last week.  But, after doing the microscope work, I'd have to say it's the very same species.  Again, I think that's Prostoia similis, but I'm waiting to hear back from Beaty.
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What we saw in pretty big numbers were the Isoperla stoneflies that provide the major hatch of "Yellow Sallies" in a lot of our streams -- Isoperla kirchneri grp. (probably I. montana).

Also showing up now, the spiny crawler mayfly, Ephemerella invaria.

These will hatch as P.E.D.'s (Pale Evening Duns) in April and May and June.  Oh, and if you look at the right rear of that nymph you'll see a little midge.  There were tons of them in the leafpacks.

So if you're fishing the fly fishing only section of the Moormans right now, I'd suggest using a Disco Midge dropper, and I'd start tying up some Yellow Sallies and P.E.D.'s for later on in the spring.