Leucrocuta flatheaded mayflies: can we ID them to the level of species?

(Note:  This is a follow-up to the entry posted on 5/9/14.)

In 1982, Unzicker and Carlson published a key to Leucrocuta species ID ("Ephemeroptera," pp. 3.72-3.73 in Brigham, Brigham, and Gnilka, Aquatic Insects and Oligochaetes of North and South Carolina).  Yesterday I decided to see what I could make of the nymphs that I've found using that key.   However, before I proceed with my results, let me note at the outset that there's a problem.  According to Beaty, entomologists are now hesitant to rely fully on that 1982 work: some of the characters used to make the ID's overlap from species to species.  A new key is being prepared.  Let's hope that addresses the shortcomings of this earlier key.

That being said, the five species that are ID'd in the 1982 key are the same five listed by Beaty as those that are likely to be found in our streams: aphrodite, hebe, juno, maculipennis, and thetis.  So let's proceed with the key having noted that there might be problems.

Using that 1982 key, I think I can safely ID three of the four nymphs -- or types of nymphs -- that I've found.  They are L. hebe, L. aphrodite, and L. thetis.    The fourth nymph -- the one in the photo at the top of the page -- is likely to be L. juno, but there's not much to go on in the key that we have.

 1. Leucrocuta hebe

Here are some of the key features to see:  "tracheae of gills distinct; pale markings on dorsum of abdominal segments 7 and 8 coalesce to form a large pale blotch; head with 3 pale spots on each side of frontal margin; a row of dark streaks present laterally on each side of venter of abdomen."  Also "V-shaped pale median triangle present on dorsum of abdominal segment 9 and covering most of middle of segment, its apex extending almost to posterior margin."  Let's have a look.

We can see all three of the pale spots at the front of the head, but only on the one side.  Also, note that the large pale spots on segment 7 don't exactly "coalesce,"  but close enough.  I'd say segment 9 matches the description.  Venter?

Yes.  There are dark lateral streaks on all of the segments.  Our key also says: "dark area present at each posterolateral angle of venter of abdominal segment 9, sometimes smaller dark area also present at each anterolateral angle of segment 9, but the dark areas are not connected to form a continuous dark margin." Not exactly what we see with the spots on segment 9, but there clearly are two spots on 9, and they are not connected.

I'd say these nymphs are Leucrocuta hebe.

I should add that Knopp and Cormier would also ID these nymphs as L. hebe (Mayflies, p.152), and our photos agree with the L. hebe photo posted by Donald Chandler (http://www.discoverlife.org/mp/20q?search=Leucrocuta+hebe).
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2. Leucrocuta aphrodite

Segments 7, 8, and 9 on L. aphrodite are the same as we find on L. hebe (pale areas on 7 and 8 coalesced: pale area on 9, V-shaped, with apex close to hind margin).    We can see that in the following photo.  We can also see the 3 pale spots on the edge of the head.

However, the "U-shaped" pale areas on segments 4 and 5 on L. hebe are not found on L. aphrodite, and on L. aphrodite, the "dark areas on [the] femora [are] usually more extensive than [the] dark areas."

The reverse is true on L. hebe.  (Visible in the photos above.)

Beaty notes that "most Leucrocuta in the Piedmont are probably aphrodite" ("The Ephemeroptera of North Carolina," p. 19).  Most Leucrocutas I find are L. aphrodite as well.  (Buck Mt. Creek, Doyles River, etc.)

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3. Leucrocuta thetis

L. thetis is described in the following way: "Tracheae of gills indistinct; pale markings on dorsum of abdominal segments 7 and 8 not coalesced; head without pale spots along frontal margin; lateral dark streaks present only on venter of abdominal segment 9."  For the lack of tracheation in gills --

I would agree.  And here's a good look at the head.

On my nymph, there are two pale dots on segment 8, very little on segment 7.

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4. Leucrocuta juno?

This nymph is very distinctive and differs markedly from the other nymphs we have seen.  Note the appearance of the abdominal segments, and the dark color of the femora with just a few pale spots. However, the description that our key provides is woefully wanting.  1) "Posterior margin of dorsum of abdominal segment 9 brown with anterior part of segment mostly pale; pale V-shaped area absent."  True.

"Gills heavily shaded with purplish-black, with paler areas at extreme tip, on inner median space next to main trachea, and near base of outer margin; dark markings at anterior of sternites 8 and 9, in median area."  The gills are heavily shaded, with pale areas at the tips and in the inner median space.

That's very good.  But, the gills on L. thetis look exactly the same!  (Look at the photo above.)  Unfortunately, I can't see "dark markings at [the] anterior of sternites 8 and 9 on my nymph."

While that might make this nymph L. maculipennis (see p. 3.75), our nymph lacks other critical features of maculipennis (e.g. "pronotum widest at anterior margin").   And, our photo matches the L. juno that Donald Chandler has posted (http://www.discoverlife.org/mp/20q?search=Leucrocuta+juno).  Were it not for that fact, I'm not sure I'd venture the guess that this is Leucrocuta juno.
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That's the best I can do at the moment.  And Beaty is right, the 1982 key is in need of revision.   Still, I think there's a pretty good chance that we can safely ID three of the nymphs that I've found: possibly all four.  Time will tell.

Oh.  One other thing.  I've only seen L. thetis and L. juno -- if I'm right about those ID's -- in small mountain streams in Sugar Hollow.  I suspect they're uncommon.

A new stream -- Staunton Run -- but nothing in the way of new insects

It was worth a try -- and the scenery was hard to beat.  I parked at the Graves Mill entrance to the Shenandoah National Park, where I look for insects in the Rapidan River.  But today I decided to hike up to Staunton Run just a half mile away.  Just spectacular!  And if I ever wanted my fly rod along, today was the day.  Staunton is a high gradient stream with boulders and riffles and pools, and those pools just had to hold native Brookies (Brook Trout).  But alas...

I was quite sure I'd see different insects today, but I'm afraid it's too late in the season.   The stream was loaded with I. holochloras (Isoperla holochlora A), one of the few Isoperlas we see in late spring/early summer.   There were too many to count.

Some spiny crawlers (E. dorothea) -- most of them fairly mature, and some showing black wing pads.   Two other things.  Clumps of submerged sticks and leaves held a lot of Roach-like stoneflies (Peltoperlidae): most of them were also mature.  Like this one.

I was hopeful that they might be the allusive genus Vieholperla, but they were not.  They were genus Tallaperla.  One of the clues -- the double thoracic gills.

The other thing I saw in large numbers -- the Northern case-makers, Pycnopsyche scabripennis.  I only took photos of one, but the only photos that turned out well were the close-ups.

The old "hot dog" case: long sticks on the sides, bits and pieces of bark in the middle.

As you can see, the sun was a bit of problem (reflection and glare).  Next year I've got to get to this stream early on in the spring.  Have to see if I can find any new Isoperlas.  And I'll probably be packing my fly rod!

A "variant form" of Isoperla orata

Nymph #1, Isoperla orata

Nymph #2, Isoperla orata, variant form

When he first saw nymph #2 two years ago, Beaty felt that it wasn't the same as nymph #1.  After close study, at the moment he feels that they might be the same -- Isoperla orata -- with nymph 2 being a variant form.  Nymph #1 was tagged as Isoperla orata some time ago (T. H. Frison, Studies of North American Plecoptera, 1942, --. 323-325).  Given the different patterns we see on nymph #2 (both head and abdominal patterns, see the entry of 5/15), it would have to be a variant form.

Beaty admits that we can't be sure of the ID of nymph #2 until someone rears it and we see the adult. In the meantime,  I'll simply call it "Isoperla orata vf."  (vf for variant form).

I have nagging doubts.  Isoperla orata vf. is a stonefly that I've found in three, quite different streams: the Upper Doyles River, Buck Mt. Creek, and the Rapidan River.  The Rapidan River is the only place I've seen I. orata.  And, when I was up there last week, I. orata vf. nymphs were a dime a dozen, I only saw one I. orata.   In fact, in four years of looking, I've only found four I. oratas.  There are differences that must be explained.
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Upper Doyles River (in winter)

Buck Mt. Creek

Rapidan River

How I take photos out in the field

Gary Williams just asked me how I take photos when I'm out in the field.  Specifically, do I ever use a tripod and/or supplemental, artificial light.  Since I've been asked this before, it might be worth covering in an entry.

I don't like to go to a stream unless the sun is shining brightly.  If there are clouds, I want them to be moving along, and I'll wait for the sun to return.  On occasion I'll use a "ring light" flash for some photos.  But I don't like the results, and for me that's a last resort on cloudy days.

Tripod?  Can't do it.  The insects I photograph are almost always moving around in the petri dish that I use (photos above and below), and I have to keep moving with them.

 When they pause, I quickly focus and shoot, almost always taking multiple shots.  I work to keep the camera as still as I can: taking multiple photos helps to compensate for camera vibration.  Taking photos this way can take a LOT of time, especially when you're dealing with stoneflies (especially Isoperla Perlodids).    They just keep moving 'round and 'round the side of the dish.  Sometimes I yell at them to stop!  (They don't seem to listen.)  Be prepared to wait them out.  You won't get a sharp photo of an insect that's moving.

I use a 60 mm macros lens:  ISO -- 100-200 (after that the quality suffers).  For shutter speed,  I'm usually at 40-80, but 80 requires really bright sunlight.

Taking the photos often takes longer than collecting the bugs.

Well, I thought it was Isoperla nr. holochlora -- but the thinking has changed

(Caution: scholar at work.)

I was in touch with Steven Beaty yesterday, exchanging e-mails on a number of issues.  In passing, I sent him this photo of one of the nymphs that I collected on Thursday, asking for confirmation that this was, indeed, Isoperla nr. holochlora.   I was concerned because of the size.  In his descriptions of Isoperla Perlodids ("The Plecoptera of North Carolina," p. 23), he gives the size range of I. holochlora as 11-44 mm; the range for I. nr. holochlora, on the other hand, is 9-10 mm.   This nymph measured 13.  His response was that rearing has shown this nymph (the one in the picture at the top of the page) to be Isoperla holochlora, but, at the moment, his group labels these nymphs "Isoperla holochlora, A."  They are still keeping tabs on this type of nymph because of the dark abdomen, on which "stripes" are difficult to detect.    So, at the moment, we seem to have two types of Isoperla holochloras.  The common one that we see,

and type "A."

He also noted, as I have seen, that both types can co-occur (i.e. show up in the same stream).  But, type "A" is the first to appear and the first to mature.  (Actually, the only place that I've seen both types of nymphs is the Rapidan River [maybe Entry Run in Greene County??]; in most streams that I visit, I only see the "common" nymph for this species.)
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I decided I had best take a very close look at his descriptions for I. holochlora and I. nr. holochlora (pp. 23-24 in his key).  There we find this.

I. holochlora -- nymphs 11-14 mm; apex of lacinia narrower at base, with row of setae below subapical tooth; pale area anterior to median ocellus open to labrum, an oval spot lateral to each side of the ocellar triangle; ocellar spot narrowly, often barely, open behind; dark, abdomen with longitudinal stripes, median stripe narrow and interrupted, often obscured.  Nymphs are common and abundant in the Mountains and Piedmont from March through August.  (I've highlighted the key features in Bold.)

Let's look at both of our nymphs to see how well they match this description.

"common"

1) "pale area anterior to median ocellus open to labrum."  Yes.  In fact there's a wide area of that spot that touches the labrum.
2)"an oval spot lateral to each side of the ocellar triangle."  Check.   (see the green arrows)
3) "ocellar spot narrowly, often barely, open behind."  Actually, on this nymph, a good portion of that spot is open behind.
4) "dark abdomen with longitudinal stripes, median stripe narrow and interrupted, often obscured."
Yes.  And the lateral stripes are "wide" and bordered by thin, pale stripes.
5)  Size?  I'm not sure about this.  I've looked at the specimens of this type of nymph in my reference collection.  Those that are fairly mature are 8-9 mm.  I'll check this carefully in a month or so when I start seeing the mature nymphs for this year.

type "A

1) "pale area anterior to median ocellus open to labrum."  Not sure that I can agree.  There is a thin point that points in that direction, but it sure doesn't touch.
2) "an oval spot lateral to each side of the ocellar triangle."  Yes.  Those we can see.
3) "ocellar spot narrowly , often barely, open behind."  Can't agree.  The spot on this nymph is surrounded by a dark border -- i.e. it's "closed."
4) "abdomen with longitudinal stripes, median stripe narrow and interrupted, often obscured."  Actually, all three stripes are fairly "obscured," but you can see them if you look at the top abdominal segments.
5) Size?  Good match.  The nymph I found yesterday was 13 mm, and it was fairly mature.

The scholar in me isn't real pleased with the way in which either nymph fits the description.  But to be fair, this document is currently being revised.
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I. nr. holochlora -- nymphs 9-10 mm; apex of lacinia narrower than base, with row of 5-6 robust setae below subapical tooth and finer setae approaching base; head with pale M-pattern and with an oval spot lateral to each side of the ocellar triangle; ocellar pale spot absent; lateral abdominal stripes wide and with pale borders, median stripe narrow, sometimes obscured. Relatively common and often abundant primarily in the Mountains.  Nymphs are collected from winter into late spring.  (Again, the Bold highlighting is added by me.)

I don't think I've ever seen a nymph that fits this description.  "head with pale M-pattern"?  No.  "ocellar pale spot absent"?  No.  That spot is clearly present in all of the photos posted above.   Now, we do see abdominal stripes of the type that are noted (lateral stripes wide with pale borders) in the common type of I. holochlora, and the size is right for that type of nymph, but it sure isn't a match.  Let me add that Beaty now feels that I. nr. holochlora as described in his key is really a new species, not a holochlora at all.

So there you have it.  We're up to speed on the issue.  Beaty has looked at my photos and confirms that both of these nymphs are I. holochlora.  So, despite my reservations, that's what I'll call them, unless I hear something else.

Chasing Isoperlas at the Rapidan River

It's one of my favorites: it's "uncommon" with a tolerance value of 0.0.  The Perlodid stonefly, Isoperla orata, which, to date, I've only found at the Rapidan River.

I only found one.  On the other hand, I found a significant number of the nymphs I've been calling Isoperla nr. orata (it's similar to I. orata but not quite the same).   Lots of these in the leaf packs.

I've already noted the ways in which these two species differ.  Still, I had a good chance yesterday to compare them, and I did note another difference that I had missed.   The "inset" at the front of the head -- the pale area anterior to the median ocellus -- is deep and straight across at the bottom on Isoperla nr. orata,

on Isoperla orata, it's shallow and rounded.

Well, I did see one other thing: note how the pronotums differ in color and pattern.

What do they share in common?  The shape and structure of the lacinia.  On I. nr. orata, there seem to be 5-6 setae on the knob below the subapical tooth; on I. orata, that number is 3.

I need Beaty to study those setae when he has time.
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I found one other insect that required microscope work: a Eurylophella spiny crawler.  (Note the large gill on abdominal segment 4.)

Beaty describes 12 species of this type of nymph, divided into 4 different groups (Beaty, "The Ephemeroptera of North Carolina," pp. 28-30).   We think we've found 3 species so far in local streams (Albemarle County).  The one that I've seen in Buck Mt. Creek is E. verisimilis, which Beaty claims is "the most common Eurylophella in the Piedmont and Mountains" in North Carolina.   And as it turned out, that's what these nymphs turned out to be.  Key features: E. verisimilis has occipital tubercles,

check, and the "submedian tubercles on terga 1-4 [are] relatively short, stout and blunt, while the turbercles on terga 5-7 are dark (and long and pointed).  Check.  (I've taken a close-up of 4-7.)

Eurylophella verisimilis, size of this one was 7 mm.

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Two additional insects.

1.  A very nice Isoperla nr. holochlora, and it was a bruiser -- 13 mm!

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and 2.  another Pycnopsyche scabripennis.  Look at the size of that case!  (Petri dish is 3" in diameter.)

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Nice spring day at the Rapidan River.  These are the two sites that I explored.

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(Oh.  By the way, yesterday I didn't find a single Isoperla montana/whatever (photo below): they were all over the place, HUGE numbers, when I was here on 4/24.  Must have been quite a hatch!)