Sunday, January 25, 2015

Moving into Isoperla montana/kirchneri season

As I mentioned last week, the Rapidan River is already chock-a-block full of these little nymphs.  It's the most common Perlodid stonefly we see in our streams.  From January to April they take over the leafpacks, hatching in large numbers in March and April to the delight of fly fisherman.  The Rapidan River must have spectacular hatches of "Yellow Sallies."

I've posted numerous entries (2/15/12, 2/16/12, 4/30/13, 4/7/14) discussing the problem of what these nymphs should be called.  If we lived in the midwest, we'd call them Isoperla namata.  But Isoperla namata does not occur in the east: the Ozarks and the midwest. But since our nymphs look just like namata, Beaty -- in his 2011 edition of "The Plecoptera of North Carolina" (p. 24) -- went with Isoperla nr. namata (Isoperla "nearly" namata) as the label to use.

In the northeast, these nymphs are called Isoperla montana (for "mountains") and Beaty later concluded that I. montana does indeed occur in our part of the country.  Still, there might be other species with nymphs that look much the same.  How about Isoperla montana/Isoperla sp. (i.e., either montana or a species that hasn't been named)?

Last year, Beaty informed me that we have at least two species that show up as this nymph: Isoperla montana and Isoperla kirchneri.   The adult of I. kirchneri has now been described (S. W. Szczytko and B. C. Kondratieff,  A Review of the Eastern Nearctic Isoperlinae (Plecoptera: Perlodidae) with the description of twenty-two new species, pp. 126-133): we're still waiting for the details on the nymph.

Quite a mess -- but the entomologists are making progress.  While we wait for the "nymph" section of Szczytko and Kondratieff to be published, let me review the forms of this nymph that I've found in the streams that I visit.  There are three.

Number 1.  Unquestionably the most common form of this nymph that I see looks like the one at the top of the page: that includes every nymph that I've ever seen in the Rapidan River.   To compare this with other forms, we have to look at two critical features.  Look at the head.

On this nymph -- on all forms of this nymph --  there is a dark transverse band on the head.  Here, that band extends down to touch the lateral ocelli.

Feature two: at the very back of the head, there are two dark bars or stripes that reach from the ecdysial suture (right behind the ocelli) to the occiput (the very back of the head).

Number two.  Now look at this nymph from South River,

and this one from Buck Mt. Creek.

We still see the dark transverse band and the bars/stripes at the back of the head.  Missing? -- the points of extension between that band and the ocelli.

Is that a significant difference?  Does it indicate a different species?  I don't know: let's hope we find out.  But I've found this form in a number of streams -- streams in which I've also found form #1 -- e.g. Buck Mt. Creek, South River, and Powell's Creek.

Number three.  And this form is unique.  Where I have found it, it's the only form that I've found.  And, I've only seen it in Sugar Hollow's small, pristine, headwater streams, higher in elevation than the other streams that I visit.

Do you see the difference?  On these nymphs, there are no dark bars or stripes running back from the lateral ocelli to the very back of the head.  (The pattern on the pronotum also looks a bit different.)

Is that a significant difference?  Does it indicate a new species?  Again, I don't know, and again, I sure hope to find out.

But I did note one thing on interest in the Szczytko and Kondratieff study.  The adult form of Isoperla kirchneri -- as I noted -- is here described for the very first time.  The name is new, thus, no one has reported on finding this species before.  But note what they say:

"We expect it to be found throughout the Appalachians at moderate elevations in relatively pristine medium sized streams."  (pp. 132-133)

Hmm...  Could those nymphs we find in those "pristine" Sugar Hollow streams be Isoperla kirchneri?
Nothing to do by wait and see.

Wednesday, January 21, 2015

Rapidan River, Part II.: Further notes on the Paraleptophlebia pronggilled mayflies

Before I start writing this entry, let me call attention to two matters of interest to at least some of our readers.

1) A major study of Isoperla Perlodid stoneflies has just been published, and it's available on line in .pdf format.  The monograph is by S. W. Szczytko and B. C. Kondratieff and is entitled A Review of the Eastern Nearctic Isoperlinae (Plecoptera: Perlodidae) with the description of twenty-two new species.  To read and/or download this monograph, go to, and click on download.  This study focuses only on the adults: the nymphs will be covered in a separate issue.

2) For new or recent readers -- all of my photos are posted on Flickr.  To view, go to, and choose the album "live photos only."  I have recently added an album entitled "personal favorites" that you might also enjoy.  Full size copies of all of the photos can be downloaded at this site.  I trust you'll cite me if you use any photos.

The leafpacks in the Rapidan River are loaded at the moment -- literally "crawling" -- with two different taxa: the Perlodid stonefly, Isoperla montana/kirchneri, and the pronggilled mayfly, Paraleptophlebia sp. (which I'm quite sure is mollis).   One of my photos from Sunday is posted at the top of the page.  And here are two more.

The gills on these nymphs, as you can see, are tracheated: the ratio is 1:3.  That's very clear in this microscope shot.

That makes it likely that these nymphs are Paraleptophlebia mollis (see Saturday's entry).   P. mollis and P. adoptiva -- on which the gill ratio is 1:1 -- appear to be, from the reading I've done, the most common Paraleptophlebias we see in the East.

When I was writing on Saturday, I assumed that the species we found was a matter of the type of stream in which we were looking.  That isn't the case.  As it turns out, each (mollis and adoptiva) has its season.   On this matter, the consensus among fly fishermen has been that P. adoptiva are in our streams first, hatching from March to May in the East: P. mollis are found later on, hatching along with P. guttata from June to August, i.e. throughout the summer.   (For confirmation, see the emergence chart in Knopp and Cormier, p. 266, and the following website,

However, Donald Chandler has reached a different conclusion.  In a note in, Chandler states (speaking about New Hampshire): "P. mollis is a winter active species, emerging in the spring and disappearing in late June, while P. adoptiva is a summer active species first appearing here in late June."  ( )Being further south in Virginia, we might expect to see P. mollis nymphs in late fall, with P. adoptiva nymphs first showing up sometime in the spring.

Obviously, this is a these that can be tested, and at the moment I think that Chandler is probably right.  It's mid-January, and at the Rapidan River I'm finding P. mollis.  As I've looked back through my photos, I find that the nymphs I've photographed in December in previous years -- in Sugar Hollow and South River in Greene County -- were P. mollis as well.

12/12/12, South River

12/13/11, Sugar Hollow

Will I continue to find only P. mollis this month and next month?  Remains to be seen.  And, will I see a changeover to P. adoptiva in the spring?  Remains to be seen.  However, one of the photos I posted on Saturday was taken on 3/3/12 at South River -- it appears to have been P. adoptiva (gill ratio of 1:1), suggesting that the change had already occurred.


Now in all of this you will have noted that I've nicely side-stepped the issue of the "spines" on segment 9: neither mollis nor adoptiva are supposed to have them, but I can see them on both in the nymphs that I've found.   This is a place where I have to read more, but from the photos I've seen that were taken by others -- and from all that I've read -- I find it hard to believe that our Paraleptophlebias are not adoptiva and mollis.

Stay tuned!  (Oh, fly fishermen.  The Rapidan must have a HUGE hatch of Blue Quills in late winter and spring, to say nothing of the Yellow Sallies (Isopera montana/kirchneri) you're going to see!)

Monday, January 19, 2015

Rapidan River, Part I.: A significant find -- Perlodid stonefly, Isoperla lata

I'm disappointed that my specimen isn't perfect: one of my other stoneflies tried to eat this nymph before I could come to the rescue!  Still, I knew when I was taking my photos that this was an Isoperla Perlodid I had not seen before.  It keys out to Isoperla lata.

I. lata -- nymphs ~13 mm; lacinia distinct, broad, apex as wide as base and covered with a dense brush of setae; head with wide, enclosed pale area anterior to median ocellus; ocellar triangle open behind; pronotum with dark border except extreme lateral margins; abdomen with longitudinal stripes, lateral stripes wide with median stripe narrow and interrupted.  Nymphs are relatively rare and are collected from the Mountains only from September through May.  Listed by NC Natural Heritage Program as Significantly Rare (2010).    (Beaty, "The Plecoptera of North Carolina, p. 24)

1. This nymph, still immature, was about 9 mm.

2. The lacinia is indeed very distinct -- very broad and very dense setae.  My microscope photo is a clear match to Beaty's description.

3.  For the head and pronotum, let's again use a microscope view.

While we still have this photo, let me quote from Frison as well (T. H. Frison, Studies of North American Plecoptera, Urbana, Illinois, 1942, p. 334).  "Dorsum of head with a small yellowish spot anterior to median ocellus, another yellowish spot in ocellar triangle, and with a large yellowish area on posterior part of head running forward on each side between compound eyes and lateral ocelli.  Pronotum with a broad, median, longitudinal, yellowish stripe, much narrower at anterior end than posterior end; areas each side of stripe brown to black."  All very clear in that photo.

4.  As for the abdominal longitudinal stripes -- they're a bit messed up since someone took a bite out of the body (the culprit will soon be revealed!), but the lateral stripes are wide, and the median stripe is "interrupted."

So we have a new one: Isoperla lata.  The Rapidan River is rich in Isoperla Perlodids.  This species will be added to our EPT taxa list.

I'll write up "Part II." of this entry tomorrow: I'll return to the issue of Paraleptophlebia species ID.  The river is loaded with pronggilled mayflies at this time of year.  But in this entry, let me include some additional photos from today's trip.  I found some beautiful insects -- as I always do when I go up to this river.

1. Giant stonefly, Pteronarcys biloba.  This was a bruiser -- close to 2 inches long.

2. One of my favorites, the Perlodid stonefly, Isogenoides hansoni.  "Relatively uncommon" according to Beaty and this is the only place that I've seen it.  (Ahem... they eat other stoneflies!)

3. Spiny crawler mayfly, Ephemerella subvaria.  Also rare/uncommon.  Two beauties today, a male and a female.



4. And of course, I saw lots and lots of Uenoids.  Just took a picture of one.  It was Neophylax consimilis, the only species I've seen in the Rapidan River at this location (entrance to Graves Mill path, SNP).


On to the pronggills tomorrow.  Today it was all about I. lata.

Sunday, January 18, 2015

Something new to explore: distinguishing the species of Paraleptophlebia (pronggilled mayflies)

My good friend in Sugar Hollow -- who is often ahead of me in doing research -- has drawn my attention to some interesting work in Knopp and Cormier (Mayflies: An Angler's study of Trout Water Ephemeroptera, pp. 268-269) on the nymphs of Paraleptophlebia (pronggilled mayflies: "Blue Quills" to fly fishermen).   They note that some gills have tracheation, others do not, and there are differences from species to species in the ratio of the length of the gill filaments (remember that Paraleptophlebia gills are "forked").  Thus, in the gill pictured here

the gill has tracheation, and the ratio seems to be 1:1, while in the gill pictured here,

while it too is tracheated, has a ratio that is closer to 1:3.  On the other hand, with the nymph in the photo at the top of the page, the gills lack tracheation, and the ratio is more like 1:5.


Super!  We have something to go on when we look at our nymphs -- and this is Paraleptophlebia season.

Of the 11 nymphs studied by Knopp and Cormier, only four are found in Virginia: P. adoptiva, P. debilis, P. mollis, and P. guttata.  As I looked at my photos this morning, I was pretty sure that I spotted 3 of these species: adoptiva, mollis, and guttata.  Have a look.

P. adoptiva?

P. mollis?

P. guttata

P. adoptiva gills have tracheation with a ratio of 1:1.  Looks good.  P. mollis gills have tracheation with a ratio of 1:3, and the gills of P. guttata lack tracheation with a ratio of 1:5.  Got them!  I was very excited.  But then I read more.  There is another distinction to make: some nymphs have "spines" or "posterolateral projections" on abdominal segment 9 -- or 8 and 9 -- while others do not.   On P. adoptiva, such spines are absent, but they seem to be present on the nymphs that I've found.

The same is true for P. mollis -- i.e., no spines on the abdominal segments.  Unfortunately my P. mollis seems to have them on 9.

But I did have one spot of success.  P. guttata does have a spine on segment 9.  And while I'm not sure you can pick out in this photo

I could see it in my microscope view, so I hope you'll trust that it's there.

So where does that leave us?  Using the Knopp and Cormier observations, I'd say I've found at least 3 different Paraleptophlebias, so far, in our streams.  One is P. guttata.  The others -- while resembling P. adoptiva and P. mollis -- appear to be unidentifed (by me) at this point.  But then Beaty notes that we should leave Paraleptophlebia ID at the level of genus, with at least 8 different species confirmed in NC: adoptiva, assimilis, debilis, guttata, moerens, mollis, swannanoa, and volitans.  (Beaty, "The Ephemeroptera of North Carolina, p. 40)  There is, I take it, a "key" to the ID of some of these nymphs, but it's in a book that's not easy to find: J.D. Unzicker and P.H. Carlson, Aquatic Insects and Oligochaetes of North and South Carolina, 1982.  A trip to the university library might be in order.  In any event, we certainly have features to look for in the nymphs that we find in our various streams.  Let's see what I run into tomorrow.

Saturday, January 17, 2015

At high elevation, some very small Uenoids -- Neophylax aniqua

Back to that pristine small stream in Sugar Hollow where we keep climbing higher, hoping to find two uncommon Uenoids: N. ornatus and N. atlanta.   And I picked up a bunch of tiny Uenoids -- all of which turned out to be N. aniqua.  This is a species that is sometimes found with N. ornatus, so we're looking in the right places.  "Neophylax aniqua usually occupies the most upstream position in the longitudinal sequence of species in streams where it occurs.  Larvae of N. aniqua occasionally occur together with larvae of N. concinnus or N. ornatus but are segregated from them by differences in periods of maximum larval growth and adult emergence."  ( R. N. Vineyard,, The Caddisfly Genus Neophylax, p. 43.)

A key feature of N. aniqua -- the stout, semi-blunt frontoclypeal tubercle can be seen even on this very small larva (4 mm).

And a second larva.  Pretty cases.

And I continue to look for our "single gill" Peltoperlid species -- Viehoperla -- but I struck out there as well.  If you look closely you can see the two gills sticking out below the hind wing pad.  This was Tallaperla.

We saw a lot of the "headwater" stream flatheaded mayfly -- Maccaffertium meririvulanum.

And we continued to pick up a lot of small Pycnopsyche gentilis (Northern case-makers) in their 3-sided cases made out of pieces of leaves.  Very young.  The heads will turn orange as they mature.  (This one might have recently molted.)

But there was one surprise.  I picked up a small piece of bark on which I found two "strong case-makers" (Odontoceridae).  I was very excited.  My friend has found Psilotreta rufa up here, a species I've never seen.  But alas, these cases were already sealed for pupation.


Next stop -- the Rapidan River.  Just need another sunny warm day.