Domination! The Perlodid stonefly Isoperla montana/n.sp.takes over South River

At the moment, the leaf packs in South River are just loaded with these little beauties, as they were in the Rapidan River last month (see the entry from 2/24/13).

This is, by far the most common Perlodid we see in our streams in the spring, though the right name to use for these nymphs remains a bit of a problem.   In Beaty's "The Plecoptera of North Carolina" posted on line in October, 2011, he referred to this species as I. nr. namata.  He went on to explain that "Isoperla namata is supposedly geographically restricted to the Ozarks and the midwest and, therefore, BAU (NC's "Biological Assessment Unit") records for I. namata may represent an undescribed species."   In April last year (personal communication, 4/29/13), he told me that these are either Isoperla montana or a similar species that has not yet been given a name (hence Isoperla n. sp. = new species).  He went on to say, "Recently, systematic work on Isoperla by Kondratieff and Szcytko has shed light on the true distribution of namata and the presence of 2 (at least) cryptic species that have the same or very similar nymphal patterns as namata.  Isoperla montana is one of those as is a new species currently being described by Kondratieff and Szcytko.  I. montana is now known to be in NC and up through ME."  He adds "n. sp. is also widespread in the east including NC and VA."

To sum up -- the Isoperla at the top of the page is either 1) Isoperla montana, or 2) a closely related species which we can call either Isoperla nr. namata or Isoperla n.sp.  (Guess we could also call it Isoperla nr. montana.)  (nr. = near)  It might soon have a real species name.

I took photos of the biggest nymph I could find.  This one measured 11 mm which is as big as they get for this species.  They're fairly mature, though I've not yet seen one on which the wing pads have turned (black).

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The other stonefly I saw in big numbers today was the Chloroperlid (Green stonefly), genus Sweltsa, and they too are getting fairly mature.  This nymph was 7 mm, and note how dark the pronotum's become.

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Mayflies

1.  This was a shocker!  The spiny crawler, Ephemerella subvaria, a species that before today I've only seen in the Rapidan River.  Pretty mature -- they'll probably hatch later in April.

2. And another spring spiny crawler, Ephemerella invaria.

3. Small minnow mayfly, Baetis tricaudatus.  They too will be hatching soon: some already have.

and a side-by-side...

3. Flatheaded mayfly, Epeorus fragilis (part of the Epeorus pleuralis group).  I'd sure like to know why this is the only stream where I see this variant of Epeorus pleuralis.  (Well, they're in Entry Run as well.)

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Caddisflies

1. Only one: the free-living caddisfly larva, Rhyacophila fuscula.  This is the one we most commonly see in our streams.

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The water was high after nearly 2 inches of rain over the weekend, and the wading was a little bit dicey.

More streams at Byrom Park --- and more Rhyacophilids

It was pretty much a caddisfly day at Byrom Park (see the posting of February the 10th), at least in terms of the photos I chose to take.  To be honest I was mainly interested in exploring new water.  I didn't venture up to the streams at high elevation -- I'll save that for spring.  Rather, I decided to look in a very small stream that was not too far from the parking lot.  This one.

Beautiful water.  But I did have to climb over some boulders and crawl through the thorns -- that wasn't pleasant!

The Rhyacophilids (free-living caddisfly larvae) in the photo at the top of the page are not R. nigrita, which is the species I found here last month.  I wasn't really sure what they were: I was not all that sure they were both the same species.  But they were both part of the Banksi complex of the Invaria Group, possibly R. banksi itself (the posting of 1/28 focussed on this complex, and you might want to look back to that entry before you proceed.)

I didn't know what to make of the head colors -- one very dark, the other golden brown.

But it turns out that that variation is common.  Weaver and Sykora (1979) on R. banksi: "Overall length 16 mm, Head: Coloration variable; in some, golden brown, in others dark brown with an irregular row of pale muscle scars extended on each side of the front and the coronal suture."  With the microscope, the muscle scars on the dark headed larva were easy to see (and see the photos posted on 1/28); no scars at all on the one with that was more lightly colored.

For the full description of this species, I'd refer you back to 1/28.  No question at all that that's what we found.

More species further upstream?  Only one way to know.
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Caddisfly number two.  The common netspinner we find in our small mountain streams, Diplectrona modesta (TV, 2.3).

I should be seeing them in Sugar Hollow as well, but nothing so far.
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And then there were the Uenoids!  Little cases all over the rocks.  I picked up a few, hoping to find a new species, Neophylax ornatus, but I think I'll have to start climbing the hills to find that one.  Today it was N. mitchelli and N. aniqua, two that I often find in the same place.  N. mitchelli, has the pointed tubercle that points towards the back of the head.

One larva actually came out of its case which allowed for some unusual photos.

N. mitchelli has ventral clavate gills on segment 1, but they were just too small to show up in these photos.
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Mayflies?  I again found Ameletids, and I saw a lot of tiny Epeorus pleuralis.  Oh, and I also saw quite a few "tiny spinys": Ephemerellas, probably E. invaria.  For stoneflies -- I saw a number of Clioperla clio Perlodids which I refused to put into my tray (they eat everything in sight!).  I did photograph a mature Taenionema atlanticum large winter and a fairly mature P. proteus Giant.

Lynch River, Buck Mt. Creek, the Doyles River -- all coming up as the water levels are finally starting to drop.
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Baetis tricaudatus and Malirekus hastatus top the list at my little stream in the Hollow

In the small streams I visit in Sugar Hollow I've only ever seen one type of small minnow mayfly: Baetis tricaudatus.  This beauty this morning -- a female -- was fully mature, in fact the wing pads seemed to be lifting off of the body.  It's back in the stream -- though it could be airborne by now!

Baetis tricaudatus is one of the least tolerant of the small minnow mayflies with a TV of 1.5.   There are two visible features that we can use for species ID.  1) Visible in the photo above -- there is a pale medial line on the abdominal segments, and 2) in the photo below -- the "middle caudal filament [tail] is less than half as long as the lateral filaments."  (Beaty, "The Ephemeroptera of North Carolina," p. 6)

Like that photo.  And here are some more.

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2. Perlodid stonefly, Malirekus hastatus.  I found a lot of them, and they're getting fairly mature: note how the rear wing pads are spreading out from the body.

I thought for the longest time that these were two different species, the second being M. hastatus, but the first being Isoperla similis.  The colors are different, and note how the abdomens differ in length.  But I guess that's a gender -- or subspecies? -- distinction.  Take a close look at the heads.  On both we can see the pale interocellar area characteristic of Malirekus and the brown lines that surround the ovate occipital areas.

Having kept the second nymph in these photos (17 mm), I decided to look at the shape of the mesosternal "Y" ridge and check for the conical submental gills.  Bingo!  Malirekus hastatus for sure.

Differences aside, they were both beautiful insects.

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3. In the leaf packs there were plenty of Giant stones to be found, some very little, but some that will be hatching later this spring.  Species?  The usual for these little streams, Pteronarcys proteus.

This nymph was close to 2 inches long: i.e. about 50 mm.
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4. And then there were the caddisfly larvae.   I finally found some Rhyacophilids (free-living caddisfly larva).  The two I picked up were still very small.  One was the quite common R. fuscula (green with the topless "H" on its head); the other appears to be another R. glaberrima (see the posting of 3/11).

This is a great stream for Rhyacophilids, and I expect to see a lot of them in April and May.

And yes, the Uenoids are still on the rocks.  I picked up two.  One was Neophylax mitchelli, the other, a little Neophylax aniqua.  Pretty case.  And the N. aniqua tubercle is visible in both of these shots.

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A beautiful morning at last: warm and sunny.   Just in time for the busiest time of the year in terms of the insects we find in our streams.

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(Oh.  This, by the way, is Isoperla similis.)

Just beautiful insects: back to the Rapidan River

The Rapidan River is chock-a-block full of insects at the moment, and a lot of them are pretty mature, getting ready for springtime emergence.  It was a sunny, early spring morning, and here are some of the beauties I found.

1. Spiny crawler mayfly, Ephemerella subvaria.  "Rare" according to Beaty ("The Ephemeroptera of North Carolina," p. 28), but there are plenty today at the Rapidan River.  By the looks of those wing pads, the "Hendrickson" hatch should be "on" up here anytime now.   The "moderately long, sharp paired submedian tubercles" (Beaty, p. 28)  are easy to see against those orange terga (5-7).

More photos:

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2. Brush-legged mayfly, genus Isonychiia.    They mature later on in the summer, but this is the stage when they're most photogenic.

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3.  Flatheaded mayfly, Epeorus pleuralis.  All over the bottoms of rocks, just like they are in a lot of our streams at the moment.  Black wing pads.  Another hatch on the way -- the "Quill Gordons."

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4. Small minnow mayfly, Baetis tricaudatus -- also with fairly long wing pads.

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5. A familiar face in the free-living caddisfly world.  The most common Rhyacophilid we see, R. fuscula.

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6. A very dark Roach-like stonefly, probably genus Tallaperla.

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7. And the most common taxa I saw -- literally hundreds and hundreds -- the Perlodid stonefly,  Isoperla montana/sp.  It's the most common Perlodid we see.  BIG hatch of "Yellow Sallies" coming up soon.

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Out again soon -- as soon as I can dry out my boots.  I got greedy at the end of the day, looking for Nemourids and ended up taking a swim.  Warm day -- but very cold water!