Saturday, February 25, 2017

Those Nemourids were genus Prostoia -- possibly Prostoia similis

The Nemourids I found yesterday at Buck Mt. Creek key out to genus Prostoia.  They're either P. completa or P. similis  At the moment I favor the latter and I'll show you why.  But, to be sure of my ID, I'm sending the nymphs to Steven Beaty for confirmation.

Let me make the case for genus Prostoia.  From Steven Beaty's "The Plecoptera of North Carolina," p. 16 (version 4.0, 2015):  Nymphs small, 5-6 mm, and stout. ... rounded pronotum with marginal fringe of short, small, irregularly spaced spines, anterior thoracic gills absent; fore tibiae with dorsal fringe of fine hairs, usually complete but sparse; ventral (inner) tibial fringe of silky setae absent; outer marginal setae of fore tibia thick, conspicuous, in two rows."

1) Two of the nymphs that I found were 5mm, one was 6.

2) The pronotum was indeed "rounded," and you can see the short, marginal spines in these pictures.

You can also note from these photos that the dorsum of the pronotum is covered with short spines (tiny black dots), something we can see in the illustration of the Prostoia pronotum in Peckarsky (Freshwater Macroinvertebrates of Northeastern North America, p. 68).

3. Anterior thoracic gills (elsewhere called cervical gills)-- these --

are absent.  Such gills are only found on Amphinemura and Zapada nymphs.   Here's a close-up of our nymph.

4. There is indeed a setal fringe on the fore tibia, as well as two rows -- marginal and inner -- of thick setae/spines.


When I got to this point yesterday, I thought I had been right some time ago when I came up with Prostoia completa for the ID.  On P. completa Beaty notes: "This is a common species in the east and possibly in North Carolina.  It occurs in small streams to large rivers."  But the key to the P. completa ID is "tibiae with a well-developed dorsal fringe of setae; cerci with short intercalary hairs present on several middle and distal segments."  The fringe of setae is well-developed, no problem there.  But what about the cerci?

  I've looked and looked but I can't see any hairs between those joints (intercalary setae).  So is there a species on which those setae are absent?  The answer is yes: Prostoia similis.  "similis -- cerci with short intercalary hairs present only on distal segments or absent altogether."  (Beaty, p. 16)

That's where things stand at the moment.  Maybe Beaty will see something with his superior equipment.  If so, I'll let you know.  Until then, my money's on P. similis, a species that has been attested in Virginia, and in SC, TN, and WV as well.

Some more photos from yesterday.

Oh!  And I almost forgot.  There's a good chance that the adult that I photographed yesterday was P. similis as well.  It's an exact match for the P. similis adult pictured on Discover Life (

Friday, February 24, 2017

Mayflies, Stoneflies, Caddisflies: A real mix today at Buck Mt. Creek

It was the kind of morning I really enjoy:  sunny, warm (74ยบ!), and the insects were plentiful, varied, and easy to find.  Let's look at some photos.

1. Large winter stonefly, Strophopteryx fasciata, pictures above and below.

There were a lot of them in the leaf packs, and some, as you can see, were fully mature.  In fact, I saw some adults flying around, and I think they were S. fasciata.  The one below landed on a rock where I was working.

I can't ID winter stonefly adults, and I found some small winter stoneflies that were also mature,

but my photo seems a good match for the S. fasciata picture that Donald Chandler has posted (

2. Small minnow mayfly, Heterocloen amplum.

This is the only one that I saw which surprised me: they ought to be out in good numbers at this time of year.  But I see them right into April, and in April they hatch.

3. Another stonefly -- a Perlodid stonefly -- Helopicus subvarians.

It's a beauty, and it's fairly common in Buck Mt. Creek.

4.  Giant stonefly, Pteronarcys dorsata.

With a tolerance value of 2.4, it's the most tolerant of Giant stones.   I've seen it before in Buck Mt. Creek, and it's the species I also encounter at the Rivanna.  A good distinguishing feature for P. dorsata is the sharply produced corners on the pronotum.

5. Common netspinner, genus Cheumatopsyche.

Actually there were two in the same bunch of leaves.


6.  But there was one thing I was really hoping to find and I did, and again I found two.  Nemouridae -- "Spring Stoneflies" or "Forestflies".

To ID these to genus and species, I need to do some microscope work.   Previous work on these nymphs has led me to two different ID's: Prostoia completa and Ostrocerca truncata.   Let me see what I arrive at this time, and I'll post my results in a separate entry tomorrow.

Great to see such variety, but it's what we get in the spring!

Monday, February 13, 2017

And the latest on I. similis is....

The nymphs I've been calling Isoperla similis must now be designated "Isoperla similis/pseudosimilis Groups."  Let me cite Beaty's words: "similis/pseudosimilis Groups -- (photographic guide: pages 33-34) -- nymphs of these two groups are currently inseparable without associated reared material.  Isoperla cherokee has been reared from various localities and provided the most nymphal specimens for study.  All specimens that match the description of Isoperla cherokee should be identifed as "Isoperla similis/pseudosimilis Groups". "  ("The Plecoptera of North Carolina," version 4.0, p. 65)

As noted yesterday, these "groups" are comprised of 7 different species: I. bellona, I. cherokee, I. starki (I. similis Group), I. pauli, I. pseudosimilis, I. reesi, and I. stewarti (I. pseudosimilis Group).  Curiously, I. similis -- I assume there still is such a species -- is not included, and Beaty notes: "no verified material of Isoperla similis, long thought to occur in NC, has been found in NC."  ("A morass of Isoperla nymphs (Plecoptera: Perlodidae) in North Carolina: a photographic guide to the their identification," 2015, p. 33)  In personal communication, Beaty tells me that all of the nymphs from VA that he has reared so far were Isoperla pseudosimilis.

Other bits and pieces of interest (photographic guide, p. 33) --

  •  species in these groups appear to be restricted to small, cold, high elevation streams
  •  preliminary morphological differences between at least some species are unproven but promising
  • can possibly be confused with the perlodid Malirekus hastatus (size and lacinia will separate)
  •  tolerance value(s) = 0.80 (even as a group, this habitus pattern is only found in high quality waters)
  • reared and positively associated: I. cherokee, I. pauli, I. pseudosimilis, I. reesi (B.K.), I stewarti (B.K.)  (note: B.K. stands for Boris Kondratieff)

Obviously, we can't do much more with the nymphs that we find until clear morphological distinctions by species have been determined.

To date, I've found nymphs of this sort in Entry Run (photo at the top of the page)

Sugar Hollow --

and the Rapidan River (for example, the nymph I found yesterday).  I've found them from February to April.

And while I'm on Isoperlas, I should note that another new species has been found in VA: Isoperla evanescens.   Detailed descriptions of this species -- both the adult and the nymph -- can be found in the recent article by Chris J. Verdone and Boris Kondratieff, "A new species of Isoperla Banks (Plecoptera: Perlodidae) from the Appalachian Mountains, Virginia & West Virginia, U.S.A., Illesia, 12 (13), pp. 74-85.

With any luck, we'll be able to nail down the ID of the nymph that we find in Sugar Hollow -- Isoperla sp. VA (pictured below) -- later this year.  Beaty plans to come up in May to take some nymphs back to NC to rear.

Saturday, February 11, 2017

Isoperla season -- and other signs of spring at the Rapidan River

So I'm about to write up today's entry and thought I'd look again at Beaty's description of Isoperla similis -- quite sure that was the ID on the nymph in this photo -- when I discovered that the playing field has changed.  In the latest version of "The Plecoptera of North Carolina," (version 4.0, December, 2015) Isoperla similis is no longer described.  Rather, we are given details on two new groups: the Isoperla similis Group and the Isoperla pseudosimilis Group.  So I turned to  Beaty's detailed study of Isoperla nymphs in North Carolina -- "A morass of Isoperla nymphs (Plecoptera: Perlodidae) in North Carolina: a photographic guide to their identification," (2015) -- where I discovered that the former group consists of I. bellona, I. cherokee, and I. starki: the latter of I. pauli, I. pseudosimilis, I. reesi, and I. stewarti.  I'm behind the times.  Let me send this nymph to Beaty to see if he can help with the ID.  But it looks like the nymphs of all of these species are as yet undescribed.  It might be that the best we can do for now is sort out into which group this nymph is is to be placed.  Stay tuned.


But this was not the only Isoperla I discovered today.

There were a lot of the smaller more common species -- Isoperla montana (Kirchneri Group).

If you're a regular reader, you know that these nymphs are prolific in the Rapidan in the spring: they're all over the leafpacks, and they hatch in April as "Yellow Sallies."  (Gear up fly fishermen!)

And another sign of spring -- the spiny crawler Ephemerella invaria.

Lots of those nymphs as well today though they were still very small.  Along with E. dorothea, these hatch out as Pale Evening Duns in May and June.  Key to the ID of invaria are the tubercles on the terga.  Notes Beaty, "abdominal terga with short, sharp, paired submedian tubercles on segments 2-9, rarely on 2, sometimes barely discernible on segments 3-8, small on 4-7, rarely on 9."  ("The Ephemeroptera of North Carolina," p. 52)

Finally, I was surprised to find 3-4 hellgrammites today, all of them Nigronia (not the common hellgrammite that we see -- Corydalus).

The species?  Nigronia serricornis.  I've found it before in some of the small streams in Sugar Hollow, but it's the first time I've seen them up here.  For the keys to the ID, look back to my entries of 11/21/12 and 11/22/12.  Serricornis is distinguished from fasciatus by the location and size of the repiratory tubes at the end of tergite 8.

These are wide apart, parallel, and relatively short (though they look large in this microscope photo).

Great fun to be out today even though it was fairly dark and cloudy.  Hope to get out to Sugar Hollow on Monday.