Domination! E. dorothea (spiny crawler) and I. namata (Perlodid stonefly) take over our streams

The number of Ephemerella dorothea spiny crawlers in a lot of our streams at the moment is simply phenomenal -- thousands and thousands.  I was at the Doyles River this morning -- my lower site, just a mile from White Hall, VA -- and I couldn't pick up a leaf pack or a submerged bundle of twigs without seeing it "crawl" with life -- little spiny crawlers.  It's just that time of the year.  Oh you will see other things in the rivers, but they're few and far between in comparison with the spinys.

At the moment I'm seeing two different colors: orange -- like the nymph in the photo at the top of the page -- and brown.

But even the brown nymphs that I found this morning weren't the same hue.  I don't think this is a matter of gender -- but I don't know that for sure.  Another point, the orange nymphs always seem to be larger than the browns.  The male in the photo directly above was 6 mm; the orange nymph at the top of the page was closer to 8.

In terms of the stoneflies that are "dominating" a lot of our streams at the moment -- they're Isoperla namatas.  These:

They're not as numerous as the E. dorotheas, but they come in a close second.  They'll be hatching real soon as "Yellow Sallies" -- to the delight of fly fishermen!

(An important note on the name "Isoperla namata."  Steven Beaty has told me again that I shouldn't be using this name unless I live in the Ozarks or the midwest.  In "The Plecoptera of North Carolina," p. 24, he uses I. nr. namata for the insect in the photo above: more recently he told me they should be called I. kirchneri or I. montana.  I have to give this some thought.  I'm happy with I. montana since I. montana looks exactly like I. namata, and I. montana is attested for PA and WV.)

In any event -- those two insects, at the moment, are the main show in town, at least in our 2nd and 3rd order streams.  Next week I've got to get back to our small mountains streams (1st order streams) in Sugar Hollow and see what's going on there.
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Other finds:

1. A small minnow mayfly, apparently Acentrella turbida -- though I've never seen one this color before.  Size: 4.5 mm.

2. And the small stonefly that is also common in at least some of our streams at the moment -- Nemouridae, genus Amphinemura.  March, April, May -- that's when we see them.

I've never seen a clean one (!), and I rarely get photos when they're fully intact.  Size: 5 mm.

One down: the Free-living caddisfly larva was Rhyacophila ledra/fenestra

The Rhyacophilid I found yesterday at the Doyles River (Blufton Road in Doylesville) appears to be Rhyacophila ledra.  R. ledra cannot be distinguished from R. fenestra, but for larvae found in the mountains, R. ledra seems to be the name that's commonly used.

R. ledra (fenestra) is described by Beaty in the following way:

(R. fenestra)/ledra -- larva 14 mm; anal proleg without apicolateral spur or basoventral hook; no ventral teeth on anal claw; segment 2 of maxillary palpi longer than segment 1; head patterned with dark muscle scars posteriorly and darkened anteriorly.   He adds: Larvae of these two species are currently inseparable.  Piedmont and Coastal plain records of R. ledra may be R. fenestra as R. ledra in NC appears to be a Mountain species while R. fenestra is primarily a Piedmont species.  (Steven Beaty, "The Trichoptera of North Carolina," p. 60)

Segment 2 of the maxillary palpi is indeed longer than segment 1 -- but I was unable to get a good photo of that.   As for the absence of ventral teeth on the anal claws -- easy to see in this microscope photo.

The dark muscle scars on the back of the head -- and on the pronotum -- as well as the change in color from front to back is clear from all of our photos, but here is a close-up.

I have drawn attention to the inward curve of the anterior row of muscle scars on the pronotum because that curve can also be seen in the illustration of R. fenestra (ledra) in the article by Prather and Morse, "Eastern Nearctic Rhyacophila Species, with Revision of the Rhyacophila invaria Group," p. 160, illustration 73A.   So we can add a new species of Rhyacophilid to our growing list of EPT taxa found in central Virginia.

One other point of interest.  This is the third free-living caddisfly species that I have found in this one set of riffles in Doylesville.

The other two species are R. fuscula...

and R. carolina.

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On the unknown Isoperla that I found yesterday -- I have a provisional ID of Isoperla orata, but that larva has been sent to Steven Beaty for further study.  More on that once I hear back from him.

More new species: up to the Doyles

This will have to be Part I. of this entry since I found three insects today that I need to ID.  This has been quite a week.  These are from the Doyles River.  My first stop was at my upper site, close to the border of the National Park; second stop -- Blufton Road.

1. The stonefly in the photo above is clearly an Isoperla Perlodid stonefly, the question is the matter of species.  It's another one that looks a bit like I . namata -- but it isn't the same.  It was small -- 8 mm -- with a dark pronotum and dark lateral longitudinal bands on the wing pads, no "dots" on the abdominal terga, and it was very hairy!  I've contacted Steven Beaty and hope to get back to you when I know more.

This is I. namata (about 10 mm):

And this is our new Isoperla:

2. I found a new free-living caddisfly larva -- a Rhyacophilid.  When I collected it, I thought it was R. carolina -- but it's not.  What is very pronounced on this one are the muscle scars on the back of the head and on the pronotum.  I think it might be Rhyacophila ledra.  More on this once I've heard something from Beaty.

3. I found two Uenoids at the upper Doyles site: I thought by now they'd all be sealed up in pupation.  But they look nothing like the Uenoids I've seen before.  I've got to get microscope photos and do more work, then I'll let you know my results.

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Phew!  Microscope work coming tomorrow.  As for the insects I found that I already knew ---

1. A large, M. pudicum flatheaded mayfly that I think was getting ready to hatch -- literally.  Note the odd looking eyes, and note that the thorax appears to be splitting so the adult can emerge!

2. Some fairly mature Chloroperlids, genus Sweltsa

3. The Isoperla Perlodid that we commonly see in the spring, Isoperla holochlora.  Happy to see this one come back.

4. The small minnow mayfly Plauditus dubius -- mature male.  This is the first one I've seen this year.

5. And this stream, like Buck Mt. Creek, is full of E. dorothea spiny crawlers.  Pick up a leaf pack and watch them crawl.

Hope to be back tomorrow with information on the identity of the mystery insects.

And another new species at Buck Mt. Creek: common stonefly, Paragnetina fumosa

One week, two new species: pretty exciting!  This always happens when I'm convinced that I've seen every species in our streams that I'm going to see.

Common stonefly (Perlidae) -- Paragnetina fumosa.  Paragnetina nymphs have a pronounced spinule row on the occipital ridge, usually lack anal gills, and are "usually distinctly patterned" (Steven Beaty, "The Plecoptera of North Carolina," p. 18).    Beaty describes P. fumosa in the following way (p. 18):

P. fumosa -- nymphs ?? mm; frons with a pair of yellow spots lateral to the median ocellar spot, median ocellar spot often congruous with pale yellow transverse band near labrum; thoracic nota with complex and extensive pattern of yellow markings; yellow femora with one sometimes two distinctive dark brown transverse bands; abdominal terga 3-4, 5 with a pair of pale markings and 8 and 9 mostly pale; anal gills present or absent.  Common and widespread except for Slate Belt and outer Coastal Plain.

I'll use two photos to point out all of those features.  The yellow spots on the frons and the distinctive markings on terga 3-5 and then 8-9 seem to me to be crucial.  (Click on photo to enlarge.)

In this second photo, I've pointed out the dark bands on the rear femora as well as the transverse band near the labrum with which the median ocellar spot is congruous.

Paragnetina fumosa -- no doubt about it.  This is a fairly tolerant Perlid with a TV of 3.6.  This nymph was about 10 mm, but note that it is not yet mature.

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Other photos:

1. A fairly mature Perlodid stonefly, Isoperla namata.  The colors were very rich, and I wish I had had better sunlight to get better pictures.

2. That little spiny crawler in the bottom right of the picture (4.5 mm) was the first Drunella I've seen so far this season: Drunella tuberculata.

3. A very colorful Ephemerella invaria spiny crawler.  E. invaria and E. dorothea clearly overlap, since Buck Mt. Creek -- like a lot of our streams at the moment -- is chock-a-block full of E. dorotheas.  If you look closely you can see the tubercles on the posterior edges of the terga (light dots).

4. A fairly mature Helopicus subvarians nymph (Perlodid stonefly).  I saw quite a few.  Black-tipped wing pads.

5. And I was happy to find another Isoperla davisi, even though my photos this time were not very good (couldn't get this one to stop in the tray).

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We have seen Paragnetina common stoneflies before, but the species we've seen previously was P. immarginata, also a beautifully patterned nymph.  (7/6/12, Rapidan River)

Isoperla davisi: a new species -- and I almost missed it!

In the first form of yesterday's entry, I called this photo one of the best pix I had gotten of an Isoperla namata Perodid stonefly.   It is a good picture: the nymph in question is not Isoperla namata.   It's Isoperla davisi, a species I have not seen before.

This is Isoperla namata.

The color's the same, and on both there are three dark stripes that run the length of the abdominal segments -- hence the reason I made the mistake.    At the moment, almost all of our streams are loaded with I. namatas, so what you expect to see can keep you from seeing what you're actually seeing!  But take a close look at the abdomen on I. namata.

The center "band" is composed of a series of lines and dots, and below the lateral stripes there are two dots on each abdominal tergite (for a total of 6 on each segment).  Now look at the abdomen of our new insect.

No dots -- just three solid stripes that are subequal in width.  How about the head patterns?

I. namata:

A dark transverse band on the head, extending back to the rear ocelli and then beyond.  What do we find on our new insect?

The head is dominated by a dark area that reaches out in all four directions, in which there are two pale areas that are enclosed.

It took me awhile to figure this out, but I finally found the description in Steven Beaty's "The Plecoptera of North Carolina," p. 24 under "I. transmarina group."  Let's see what he says.

I. transmarina gr. -- consists of both I. davisi and I. transmarina.  Nymphs 10-14 mm; apex of lacinia narrower than base and constricted medially, with row of 5-6 stout setae below subapical tooth; pale area anterior to median ocellus enclosed (davisi) or not enclosed and open in front (transmarina); width of triangular pale spot in ocellar triangle about one half the distance between the lateral ocelli, possibly open behind (transmarina) or closed behind (davisi); longitudinal abdominal stripes subequal in width, with narrow pale borders.  (I have underlined those portions that deal specifically with I. davisi.)

Unfortunately -- or fortunately, in terms of the gene pool! -- I did not keep this nymph, so I cannot verify the size, nor can I provide a photo of the lacinia.  However, the lacinia as described does not vary a lot from that of I. dicala which you can see in yesterday's entry.  But Beaty's descriptions of the head pattern and the abdominal stripes are dead on for those of our nymph.  It's I. davisi.

There is something else that supports this conclusion.  Beaty mentions that there are pictures of the nymph and adult of I. davisi in a book by Pescador.  The book in question is: Manuel L. Pescador, Andrew K. Rasmussen, and Baron A. Richard, A Guide to the Stoneflies (Plecoptera) of Florida, which was published in 2000 by the State of Florida's Department of Environmental Protection.  There is a downloadable pdf. version of that text on line at: http://publicfiles.dep.state.fl.us/dear/labs/biology/biokeys/stonefly.pdf.  On p. 77, there are pictures of the head and abdomen of I. davisi (a nymph): they are an exact match for the nymph that I found yesterday at Buck Mt. Creek.

Cool!  There is, by the way, a photo of I. transmarina available on line at http://www.discoverlife.org/mp/20p?see=I_DSC549&res=640 ("Discover Life," Donald Chandler) if you want to compare the two.

I. davisi -- common name, "Alabama Stripetail" -- is attested in South Carolina, Florida, and Alabama: Beaty implies that it has been found in North Carolina as well.  I'm not sure if it has been found before in Virginia.
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Additional photos:

Always fun to find a new species.  Now, of course, I don't understand how I confused this with Isoperla namata!