Doubling up on Caddisflies: Back to Sugar Hollow

Another "rare" day of sunshine, so this morning I headed off to my favorite small mountain stream in Sugar Hollow.  Lots of insects.  But I seemed to score best with the caddisfly larvae.

In the photos above, a pair of free-living caddisfly larvae, Rhyacophila nigrita.  It's one of the species I commonly find in this stream.  Sometimes the body is white; sometimes -- as here -- it's aquamarine.  R. nigrita is described by Beaty in the following way:

R. nigrita -- head black or brown and parallel sided; pronotum darker anteriorly. Occurs mostly in small Mountain streams.  Third most common Rhyacophila in NC.  ("The Trichoptera of North Carolina," p. 61)

The Appalachian mountains, by the way, are rich in Rhyacophilids, and the R. invaria group -- which includes R. nigrita -- is the subject of a very important study: Aysha Lynn Prather and John Chapman Morse, "Eastern Nearctic Rhyacophila Species, with Revision of the Rhyacophila invaria Group," Transactions of the American Entomological Society 127 (1): 2001, pp. 85-164.  They note that the 14 species of the R. invaria Group are "endemic to the Appalachian Range." (p. 86).
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But another double shows up in my photos -- the common netspinners that we find in these small mountain streams in the spring, Diplectrona modesta.   D. modesta and D. metaqui are both attested in North Carolina.  Both have a "submedial dark U-shaped pattern" on the frontoclypeus, and a "dark pattern posterior to and along the frontoclypeal sutures." (Beaty, "The Trichoptera of North Carolina," p. 74)  But they differ in one respect: there is an asymmetrical notch in the anterior margin of the head on D. metqui, but not on D. modesta.  These are D. modesta.

And a couple more photos.

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I also doubled up on Uenoids today.  I found two different species in the very same part of the stream: Neophylax consimilis and Neophylax mitchelli.  Remember that N. consimilis has a pale area or stripe on the head, while N. mitchelli is distinguished by a long, pointed tubercle on the head.  Both have "well developed clavate ventral gills on abdominal segment 1." (Beaty, "The Trichoptera of North Carolina," pp. 86-87.)

Neophylax consimilis:

Neophylax mitchelli -- pictures of three different larvae.

#1

#2

#3 (very small)

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Other findings and photos.

1. A fairly big Limnephilid caddisfly larva (case about 1 inch long), Pycnopsyche gentilis, the one that makes the three-sided case out of sections of leaves.  (The "cling-ons" are a mature large winter stonefly, T. atlanticum, a tiny E. invaria spiny crawler, and one of the D. modesta netspinners.)

2. Perlodid stonefly, Malirekus hastatus.  I found two -- neither one is mature.  (Their heads are too big for their bodies.)

3. Flatheaded mayfly, Epeorus pleuralis.  Lots of them on the bottoms of rocks.

4. And a Chloroperlid stonefly (green stonefly).  This is the most common taxon I saw today.  Unfortunately, I discovered that the M. hastatus Perlodids like to eat them!

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Sugar Hollow: a small mountain stream in the winter.

Isoperla season at the Rapidan River

If you follow this blog in a regular way, you know that the streams in our part of Virginia -- especially those in or near the mountains -- are rich in Isoperla Perlodid stoneflies (sometimes called "stripe tails").  The most common species we see is Isoperla namata, and I saw them in large numbers today.  But the Perlodid in the photo above is a small Isoperla nr. holochlora.  I was surprised to see one this early, but the Rapidan is the only stream in which I've seen this particular species.  (For a list of the Isoperlas I've found, so far, in our streams, see the entry posted on 9/8/12: for photos, see the entry for 10/3/12.)

The "nr." in Isoperla nr. holochlora stands for "near," since this species looks a lot like Isoperla holochlora.  But we can tell them apart with no need for a microscope view.  There are two things to check: 1) does the front part of the large yellow spot on the head merge with the labrum, or just barely touch it?  2) are there obvious longitudinal "stripes" on the abdominal segments?  If it's Isoperla nr. holochlora, the answers are "no": if it's Isoperla holochlora, the answers are "yes."  Have a look at these mature nymphs from last year.

They're both beautiful stoneflies.  But the Perlodid that we're more likely to see -- and in the spring, we see a lot of them in a lot of our streams (TV is 2.5) - is Isoperla namata.  This one.

They were a dime a dozen today in the leaf packs, and note that the wing pads on the nymph in the second photo are already starting to spread out from the body.
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The I. nr. holochlora was a surprise in my findings today: so too was this little small minnow mayfly, even though I was hoping to see one.

Baetis tricaudatus -- the first of the year.  This is a fairly intolerant small minnow mayfly with a TV of 1.5, so we only see it in clean mountain streams.  I've found them in the Rapidan, the South river in Greene county, and in some of the small streams in Sugar Hollow.  There are two ways to tell this one if you're using a loupe: 1) B. tricaudatus nymphs have a short, center tail with no banding on the tails, and 2) they have a thin, pale stripe that runs down the center of the abdominal segments.

And when they're mature they look like this (Rapidan River last winter).

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For the most part, I saw insects today that I expected to see, but the variety in this stream is really amazing.

1. Flatheaded mayfly, Epeorus pleuralis.  This is the most common insect I saw on the bottoms of rocks.

The wing pads are fairly long on this one as it prepares for the early spring hatch of "Quill Gordons."

2. Pronggilled mayfly, genus Paraleptophlebia.  These were common in leaf packs.

3. Spiny crawler mayfly, Ephemerella subvaria.  Always a favorite.

4. Spiny crawler mayfly, Ephemerella invaria.  Note the pale yellow stripe between the eyes.

5. Common netspinner caddisfly larva, Ceratopsyche alhedra.  This is the only common netspinner species I've seen up here in the winter.

6. Freeliving caddisfly larva, Rhyacophila fuscula.  This was a BIG one, probably an inch long.

7. Humpless case-maker caddisfly larva, Brachycentrus appalachia.

8. Lepidostomatid case-maker caddisfly larva, genus Lepidostoma.  I've never seen "mixed media" cases at the Rapidan River.

9.  Uenoid caddisfly larva, Neophylax consimilis.

10. And Uenoid caddisfly larva, species to be determined.

The water remains high in most of our streams -- but at least there was sunshine today!

Neophylax concinnus as the Uenoid I found at the Doyles: Making the case

The Uenoid caddis that I found yesterday at the Doyles appears to be Neophylax concinnus.  I'm not yet totally certain of this ID, but the evidence that I've compiled points strongly in that direction.  Let me make the case as I see it, approaching the issue in three different ways.


I. Elimination of other choices.

Steven Beaty's description of N. concinnus is brief: "without clavate ventral gills on abdominal segment 1."  ("The Trichoptera of North Carolina," p. 86)  That is certainly true of this larva.  Have a look.

I. e what is missing are these -- the balloon-shaped gills we find, for example. on N. oligius.

Of the Neophylax species that Beaty describes (pp. 86-87), only four lack clavate gills: N. aniqua, N. concinnus, N. toshioi, and N. fuscus.  Of these, N. aniqua and N. toshioi both have a "prominent tubercle on [the] head, often semi-blunt."  (Beaty, pp. 86-87)  The tubercle on N. aniqua looks like this:

There is no such tubercle on the larva I found yesterday.  There "might" be a very small, "pimple-like" tubercle on the head, but if there is, it's too small to show up in any photo I've taken.  But we can eliminate these three other species in additional ways.  N. aniqua, you will recall, is found in first order/headwater streams: this larva was found at a downstream location in the Doyles, close to its confluence with the Moormans.  N. toshioi, in addition to having a prominent tubercle on its head, has a head with a "pale eye stripe laterally" (Beaty p. 87) -- not true of our larva -- and it has "lateral gills on abdominal segments 2-5."  Our larva appears to lack lateral gills.  Finally, N. fuscus, like N. aniqua is a "headwater" taxon which is "relatively rare."  (Beaty, p. 87)

II. Confirmation of key features.

In. R. N. Vineyard, G. B. Wiggins, et.al., The Caddisfly Genus Neophylax, p. 46, we read: "Among larvae lacking gills on abdominal segment I [i.e. clavate gills], that of N. concinnus is distinguished by a combination of traits: short spines along the anterior margin of the pronotum, frequent presence of a small frontoclypeal tubercle, and pronotum with microsculpture of transverse rows of spicules."

1. There are short spines on the anterior margin of the pronotum of our larva.  But they are not easy to see through the layer of silt at the pronotum's edge.

2. As noted before, there "may" be a small frontoclypeal tubercle on our larva -- I'm not really sure.  However, the word "frequent" suggests to me that the tubercle is not always there and certainly not prominent.

3. And I think I can see a "microsculpture of transverse rows of spicules" on the pronotum.  The tiny black dots on the pronotum are very small spines.

This source also notes that there are spicules on the posterior of the mesonotum.  Those are quite clear in this photo.

III. Location, location, location

Vineyard, et.al., note that N. concinnus "occupies a wider array of habitats than any other single species in the genus" but that "it is generally found in small second- and third-order streams."  (p. 48)  I'd say that the Doyles fits into that group; I'd call it a second or third order stream.  Of greater interest still, this source notes that "Beam and Wiggins (1987) found that in southern Ontario streams N. concinnus occupied the longitudinal zone between N. aniqua (upstream) and N. oligius (downstream)."  (p. 48)  Perfect!  The N. aniqua larva I found was in a small stream in the Blue Ridge; the Doyles River near Whitehall is about 3 miles east of the Shenandoah National Park; and Buck Mt. Creek, where I normally find N. oligius larvae is about 10 miles more to the east.  So stream size and location also work in favor of this ID.

As I've already said, for me, at the moment, this ID is a tentative one.  I'll be sure to return to the Doyles very soon to see if I can find better samples.

N. aniqua

N. concinnus?

N. oligius