Cold fingers -- but beautiful stoneflies at Buck Mt. Creek

Still hampered by cold temperatures, cloudy skies, and high water.  But as cold as it was at the start of the day (25º when I got up), the sun was out without a cloud in the sky, so I decided to see what was up in Buck Mt. Creek.  The water was high and a little off color, but when I could find leaf packs I could find stoneflies -- and there were some beauties today!

1. Perlodid stonefly, Clioperla clio.  Tolerance value, 5.2.  Why some are orange and others are yellow I don't really know, but I photographed one of each.  This is one of the first Perlodid stoneflies we see in the fall and we'll see it well into the spring.  More photos.

and the yellow one...

2. Perlodid stonefly, Helopicus subvarians.  Tolerance value, 1.2.  Beaty says this one is "relatively uncommon," ("The Plecoptera of North Carolina," p. 21), and I suppose that it is overall, but I see a lot of them at my site in Buck Mt. Creek.  I found four in a hurry this morning, but I only took photos of one.  Still not quite mature.

3. Large winter stonefly, Strophopteryx fasciata.  Tolerance value, 3.3.  So disappointed.  I had one that was fully mature with black wing pads, but I managed to lose it!  Still, this is a nice looking insect.

4.  And for the surprise of the day -- a Giant stonefly, Pteronarcys dorsata.  Tolerance value, 2.4.  I think of this as a summer/fall insect -- and Beaty says "most abundant from June to October" (p. 28) -- but this one's still here in late winter!  I would guess the orange bands on either side of the pronotum are a sure sign that this nymph is mature.

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Nothing new out there today, but the sun was right for good photos.

The Rapidan in winter: pronggilled mayflies, I. montana Perlodids, and lots of Lepidostomatids

But before we talk about the dominant taxa...  When I picked up this gorgeous Perlodid, I thought I'd found something new -- and it is new, for me, for the Rapidan River.  Before today, I'd only found this one in the small streams in Sugar Hollow.  Isoperla similis: tolerance value, 0.8 and "relatively uncommon" (Beaty, "The Plecoptera of North Carolina," p. 24).  I think I've ID'd it before, but it's worth another look.  Here's Beaty's description:

I. similis gr. -- nymphs 12-15 mm; apex of lacinia slightly narrower than base and slightly constricted medially, with row of 4-5 stout setae below subapical tooth; head brown with a pair of pale spots near labral suture, a pale M-shaped mark anterior to median ocellus and pale marks anterolateral to the lateral ocelli; abdomen brown with a light median longitudinal stripe and with a pair of faint submedian pale dots on each segment.  Head and body covered with dark clothing hairs. ... Collected from headwater Mountain streams and medium rivers during the winter and early spring.

1. This nymph was 13-14 mm.

2. The lacinia matches the description, though I count 5-6 stout setae below the subapical tooth.

3. The head is as described.  Have a look.  (You can also see the "hairy" body in this photo.)

4. And for the abdomen, the medial stripe and the submedian dots are clear.

Isoperla similis, and I guess we could call the Rapidan a "medium" river at this location.
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And another beauty this morning -- Giant stonefly, Pteronarcys biloba.  This measured about 1 3/4" -- about 45 mm.

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But the dominant taxa -- Perlodid stoneflies, Isoperla montana/sp., pronggilled mayflies, the little case-maker Lepidostomatid, and on the rocks -- the flatheads Epeorus pleuralis.   I easily saw over 100 I. montanas in sorting through 10-12 leaf packs in one small part of the stream.  What a hatch of "Yellow Sallies" there must be up here in the spring!

1. Isoperla montana/sp.  (Caught one eating a pronggilled mayfly.)

2. Pronggilled mayfly, Paraleptophlebia sp. (mollis?).  One that survived being in a tray full of I. montanas!

3. Flatheaded mayfly, Epeorus pleuralis.

3.  And some of the many, many Lepidostomatids.

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The Rapidan was high and fast and I was restricted to looking at leaf packs and rocks that were in close to shore.

Back to the streams! The northern case-maker Pycnopsyche gentilis

It's been a long two weeks: 18 inches of snow, 1-2 inches of rain, and now warmer temps = streams that are flowing out of their banks.  Even the small streams in Sugar Hollow are still high and fast.  But I was determined to see some insects this morning.

And this is one of the taxa I was hoping to find: the first Limnephilid (northern case-maker) of the season, Pycnopsyche gentilis.  This is the caddis that -- in its early instars at least -- makes a three-sided case of neatly cut sections of leaves.  Like the Uenoids we're seeing right now, these larvae will pupate through the summer and emerge in the fall as "Great brown autumn sedges" (Thomas Ames, Caddisflies, pp. 252-257).

I've keyed out this species in an earlier entry (9/14/12), to which I urge you to turn.  However, one of the defining features for species ID is the lack of a dorsal hump on abdominal segment one, which we can clearly see in this photo.

This is a larva we'll see right into April, but by then many will have built new cases of gravel.

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Uenoids.   I only picked up a couple, both of them, to my surprise, were Neophylax mitchelli: clavate ventral gills and a prominent frontoclypeal tubercle, one that points to the rear of the head.
Like most of the Uenoids I find in this stream, both made beautifully colorful cases.

#1

#2

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Mayflies.  I saw a number of Maccaffertium flatheads, some pronggilled mayflies, and one tiny spiny crawler (Ephemerella).  But the bottoms of rocks were covered with Epeorus pleuralis flatheads -- as they commonly are at this time of year.

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Stoneflies.  Lots and lots of the large winter stonefly Taenionema atlanticum, and I saw a lot of the adults flying around.  My photos did not turn out as well as I wished: somehow antennae got broken.

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And this is where I was wading -- very carefully, I might add!

Back out on Monday.  I might risk a trip to the Rapidan River.

Heterocloeon amplum: the small minnow mayfly we'll see when we can get back into the streams

It's been a tough winter, and the 16 inches of snow Wednesday night sure didn't help.  It's melting. But at the moment I have no place to park near the streams.  I'll see if I can get out tomorrow.

In the spring and summer I see a lot of different small minnow mayflies: in the winter, I normally see only two: Baetis tricaudatus -- in small, very clean mountain streams -- and Heterocloeon amplum in somewhat larger streams further away from the mountains (Doyles River, Buck Mt. Creek, Lynch River, etc.).  I thought I might review the identification of H. amplum nymphs for those of you who will soon return to sampling.

The colors of H. amplum nymphs are normally gender specific.  Females are olive --

males tend to be olive/brown.

Both of these photos, by the way, were taken on February 6th, 2012 -- so you can see what we're missing!

While the colors may vary, morphologically males and females are exactly the same.  They differ from the other Heterocloeons in that they lack procoxal gills, and unlike H. curiosum, they do not have a dark spot in the central part of the gills.  I.e. they don't look like this:

Here is Beaty's description ("The Ephemeroptera of North Carolina, p. 9):

H. amplum -- nymphs 7-9 mm; unique labial palpi (parallel sided); shortened leg setae; femora, tibiae and tarsi relatively shortened, tarsi slightly dilated apically with wide, pale medial band; gills large, suboval, with rudimentary trachea.

1. palpi parallel sided

2. shortened leg setae

3. dilated tarsi with pale medial band

The gill tracheation is a little bit tricky.  In normal light, it certain is simple: a thin line in the center with 1-2 finer branches.

However, if the sun shines through the gills, we can see very fine tracheal branches.

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So we know what to look for in microscope views.  But can we recognize H. amplum nymphs at the stream?  I think that we can.  For one thing, the only other small minnow mayfly we're likely to see -- Baetis tricaudatus -- has three tails ("three" caudal filaments), H. amplum nymphs have only two.

But the thing that strikes me as really unique is the color of tergites 4 and 5: both tergites are orange on the males, yellow/orange on the females, with paired dark medial spots.

Terga 6-8 are dark; 9 and 10 are light.  This color scheme is easy to spot even on very small nymphs like the one I found on 1/20 this year.

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Only one word of caution.  Late in the season (late March, early April) you might see some H. amplums that look a little bit different --

they're totally black.  The reason?  I suspect it's because these nymphs are completely mature and ready to pop.  I've seen the same thing with brushlegged mayflies.

Even so, if you look closely  at the H. amplum nymph, it's clear that terga 4 and 5 are lighter that 6-8.
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(Oh.  And for the fly fishermen -- H. amplum is the biggest small minnow mayfly we see.  I'd use a size 14 hook -- maybe even a 12 -- when the Blue Winged Olives hatch in the spring.)