Saturday, May 18, 2013
1. Isogenoides hansoni -- at the Rapidan River (in the photo above): TV, undetermined (too rare)
2. Isoperla nr. holochlora -- at the Rapidan River: TV, 0.0
3. Malirekus hastatus -- at the Rapidan River and in the small streams in Sugar Hollow: TV, 1.0
4. Isoperla similis -- small streams in Sugar Hollow: TV, 0.8
5. Isoperla sp.1 (species unidentified): small streams in Sugar Hollow: TV, undetermined
6. Isoperla sp.2 (species unidentified) -- small streams in Sugar Hollow: TV, undetermined
(Below -- one of the small streams in Sugar Hollow in which species 3-6 have been found.)
Buck Mt. Creek originates in the northern part of Albemarle county, not far from the boundary of the Shenandoah National Park. I look for insects 10-12 miles southeast of that location at the junction of Catterton Road and Free Union Road, 2-3 miles east of the town of Free Union. I remember it being rated a little bit over average when I monitored streams. Still, my impression is that it's the "richest" stream that I visit in terms of the variety of aquatic insects it holds: mayflies, stoneflies, caddisflies, dragons and damsels, diptera and beetles. One of these days I intend to compile a list of the EPT species that I've found in that stream since I started writing this blog.
And it's a "factory" for Perlodid stoneflies. I've found more Perlodid species in BMC (Buck Mt. Creek) than in any of the streams I explore, with the possible exception of the Rapidan River. So I thought I should publish the list, with photos, noting the tolerance values. I'll divide them up by season, noting the months when we're most likely to see them. Most of these photos were taken at Buck Mt. Creek.
I. Fall, Winter: October -- March
1. Clioperla clio: TV, 5.2
2. Diploperla duplicata: TV, 2.8
3. Helopicus subvarians: TV, 1.2
II. Spring: March -- May
4. Isoperla montana/n. sp.: TV, 2.5
5. Isoperla davisi: TV undetermined
6. Isoperla dicala: TV undetermined
7. Isoperla sp. (possibly I. orata): TV, 0.0
III. Spring - Summer: April -- June
8. Isoperla holochlora: TV, 0.7
9. Remenus bilobatus: TV, 0.9
Nine species -- well, nine species and counting. I won't be surprised if this list continues to grow.
Buck Mt. Creek remains one of my favorite streams in the county in terms of insect populations -- and I admit to being partial to Perlodid stones!
(The riffles pictured at the top of the page and in the photo below are the two sites where I find most of these insects.)
Friday, May 17, 2013
The spiny crawler, Drunella walkeri. I've seen them before -- in the Doyles River and in Buck Mt. Creek -- but I've never seen one with these incredible colors. Wow!
Actually, one of the things I was hoping to find today at the Doyles was a Drunella, but I was looking for Drunella cornutella. This:
I found this one on May 26 of last year at my "upper" Doyles site, close to the boundary of the Shenandoah National Park, which is where I started looking for insects this morning. No luck. But when I stopped at my lowest site on the Doyles, about 1 mile north of White Hall, I found a lot of Drunellas, but D. walkeri (TV, 0.6) and D. tuberculata (TV, 0.0). But this walkeri was pretty special.
D. walkeri is described by Beaty in the following way: "nymphs 8-10 mm; body setose; head roughened, with only small occipital tubercles and barely discernible lateral frontoclypeal projections; genae produced into sharp anterolateral projections; forefemur with long hair; abdomen with paired dorsal tubercles always well developed on segments 5-7. Collected in late winter through spring. Uncommon in the mountains." (Steven Beaty, "The Ephemeroptera of North Carolina," p. 26)
The body is indeed very setose (hairy) as you can see in this photo: you can also see the long hair on the fore femora. (Click on the photo to enlarge.)
And the tubercles on the posterior edges of the abdominal tergites show up as white dots on this particular specimen.
Quite a find. It was even colorful when I flipped it on its back.
One of those insects that makes your day.
Not nearly so colorful as our D. walkeri, but interesting nonetheless. On D. tuberculata, Beaty has the following things to say. (p. 25)
D. tuberculata -- nymphs 7-9 mm; head with long occipital tubercles not divergent apically; frons without dark transverse band; abdomen with paired dorsal tubercles always well developed on segments 5-7. Collected in spring and summer from rivers. Uncommon. Primarily a Mountain species.
Here is a good view of the occipital tubercles, and they clearly do not diverge apically, they might even slightly converge. You can also see in this photo that there is no dark band on the frons (the face).
The tubercles on segments 5-7 are well developed though they might not be as clear as I would like in this photo.
(For more detail on how we identify D. tuberculata, see the entry of 4/23/12.)
Knopp and Cormier (Mayflies, pp. 224-227) do not mention D. tuberculata as important to fly fishermen, but they do list D. walkeri as one of five Drunellas that hatches as the "eastern blue-winged olive." D. walkeri hatches in the northeast from July through September -- probably in June and July down here. It must be a fairly big mayfly: BWO's (vs. "eastern BWO's" are normally small, hatching from small minnow mayflies primarily in the spring and fall.
If you want to look for these nymphs, stick close to shore and look in patches of thick vegetation (leaf packs, root balls, bunches of twigs). They will be in flowing water, but I never find them out in the fast flow of the stream. Also look at the bases of patches of grass in the water. Three of the five nymphs that I found this morning were on a small piece of bark submerged in the water.
They are often dirty, even covered in silt -- like this D. walkeri, one that I also found in the Doyles this morning. Not all of them are as clean and colorful as the one at the top of the page. But when you're crawling in root balls with those hairy legs and hairy body, this is what happens!
Thursday, May 16, 2013
This morning I went to a small mountain stream in Sugar Hollow, one of the seven that I visit in a fairly regular way. I saw quite a few Perlodid stoneflies -- Isoperla holochlora, Remenus bilobatus, and that unknown Isoperla on which I focussed last week (5/10). But the leaf packs were loaded with spiny crawler mayflies -- Ephemerella dorothea from what I could see -- which is true of leaf packs in just about all of our streams at the moment.
It's their time of year. This may be the single most prolific insect we find in our streams, and they show up in April and May. When I monitored streams, I remember being disappointed when samples were dominated by spiny crawlers. That had a negative impact on the "score" of the stream. In Virginia, to begin with (unless things have changed), all spiny crawlers -- every genus and species -- are given a tolerance value of 4 (scale of 1 to 10), and whenever one insect family accounts for, say, two thirds of the sample, the stream is seen to be lacking in the variety that's always desired (which also brings down the score. Also, I never found them very attractive.
Point one: scores are bound to be skewed if every genus and species of a particular insect are given the same tolerance value. Most of the spinys that we see at the moment are E. dorothea with a TV (in North Carolina) of 3.3, but we also see E. invaria (TV, 2.6), Drunella tuberculata (TV, 0.0), and Drunella walkeri (TV, 0.6).
Point two: at this time of year, we are bound to get samples that are dominated by spinys -- it's inevitable. And the lack of variety in our samples does not indicate that we're dealing with so-so streams. The stream that I went to this morning was a head-water stream, a first order stream, one that is filled with quality insects. Still, this morning, spiny crawlers probably accounted for 75% of the insects I saw.
And point three: if you think that spiny crawlers are "ugly," you're not looking at them very closely (which is true if you're just picking them off of a net). Look at that beauty at the top of the page. And here are more photos that I took this morning, all E. dorothea, three nymphs that differed in color and pattern.
Tis the season folks: take a close look and enjoy!
Just one other photo -- a very nice Isoperla holochlora. They too are very numerous at the moment in these small mountain streams. Tolerance value: 0.7.
Tuesday, May 14, 2013
This is one of the flatheaded mayflies -- genus Rhithrogena -- that I found at the Lynch River on 5/2, and in the entry posted that day, I noted that I hoped I could ID these nymphs to the level of species. I've worked on the problem: I haven't resolved it. Let me show you why I'm still up in the air.
In his "Ephemeroptera of North Carolina" (p. 22), Steven Beaty describes seven species of Rhithrogena that occur in that state: R. amica, R. exilis, R. fasciata, R. fuscifrons, R. manifesta, R. rubicunda, and R. uhari. Given the size of our nymphs -- 5 mm -- and the general color and pattern of the abdomen and the head, I'd say we can eliminate all but two of these species: R. fasciata and R. uhari. These are described in the following ways (Beaty, p. 22):
R. fasciata -- nymphs 5-7 mm; tergites orange or orange brown. Spring and summer in Piedmont and Mountains.
R. uhari -- nymphs 5-7 mm; abdominal tergites light chestnut or cinnamon brown, with no pattern. Collected in winter and early spring.
So, what do you say? Is that abdomen "orange brown" or "cinnamon brown"? It does, I think, have a "pattern," so I was tempted to go with R. fasciata. But I decided to look into this further. I'm afraid that what I found just complicated the issue.
Let me begin with a reminder that I've found Rhithrogena in two of our streams: the Lynch River and Buck Mt. Creek. Here are photos of two of the nymphs that I found in Buck Mt. Creek in 2011.
With the sub-triangular white spot on its head, this second nymph is really quite striking, and I thought it might be a genetic anomaly. But then I saw Donald Chandler's photos of Rhithrogena on "Discover Life" (http://pick5.pick.uga.edu/mp/20q?search=Rhithrogena%20jejuna&btxt=microscope&burl=htpp://microscope.mbl.edu). He posts a photo of that very same nymph: it's Rhithrogena jejuna! And if you look at that page, you'll see another photo of R. jejuna which looks exactly like the nymph in the first photo, the one I found on 4/30/11.
I have to conclude that the Rhithrogena I find in Buck Mt. Creek is R. jejuna, a species that does not occur in North Carolina, but one which is found in the Northeast and the Midwest. And, it is an insect that is important to fly fishermen. Look, for example, at Ernie Schwiebert's Nymphs, Volume II: Stoneflies, Caddisflies, and other Important Insects, Including the Lesser Mayflies (p. 485). "The first of nine Rhithrogena species important in my experience is the eastern and midwestern Rhithrogena jejuna. It is the first of the genus to emerge on eastern and midwestern rivers, hatching from the close of the first week in May until Memorial Day." And R. jejuna, along with R. impersonata, is described in Knopp and Cormier (Mayflies, p. 139): "The occasionally encountered East-Midwest species R. jejuna and R. impersonata (synonymous with R. sanguinea) are pale olive brown and bright reddish brown, respectively, which, with their shape, makes them easily distinguishable from other mayfly nymphs that inhabit this region's streams and rivers."
"Pale olive brown"? I think I can buy that. That would mean that our Rhithrogenas (those in Buck Mt. Creek) are the same (R. jejuna) as those that occur in the Northeast and aren't connected to those that are found further South.
But what about those we find in the Lynch? I've found two types of Rhithrogenas up at the Lynch, two different colors. One looks like it, too, could be R. jejuna. For example, this nymph that I found there last year...
and this one as well, which I found on 5/2 of this year along with the one at the top of the page.
Still, most of the nymphs that I found this year were much darker in color...
and I also found dark brown nymphs in the Lynch River last year, this one on 3/28.
I have trouble going with "pale olive brown" for these darker nymphs, i.e., I doubt that they are Rhithrogena jejuna. But we have three other choices:
R. impersonata (bright reddish brown) -- Knopp and Cormier, Northeast and Midwest
R. fasciata (orange brown) -- Beaty, North Carolina
R. uhari (cinnamon brown) -- Beaty, North Carolina
This is where I give up. I really can't make such fine distinctions in color. Since R. jejuna seems to occur in our streams, perhaps these are R. impersonata, the other species that is common in the Northeast, and some of Chandler's photos of R. impersonata could be used for confirmation (http://www.discoverlife.org/mp/20q?search=Rhithrogena&guide=Groups_Insecta&mobile=iPhone). But "orange brown" and "cinnamon brown" seem to be good color choices as well.
That's where things stand at the moment. This one I haven't resolved.
Friday, May 10, 2013
this is another one, and I found a lot of these nymphs this morning. It's an odd color for Isoperla -- light brown, with a pronounced pale spot in the ocellar triangle, and the abdominal stripes are not all that easy to see (especially the lateral stripes).
We found this species last year -- even in 2011 -- and in May of 2011 I sent some to Steven Beaty to help with ID. His reply was "species unknown." Were we to raise these to maturity in a lab setting, we might find that it is a known species as an adult -- but the association with this particular nymph has not yet been made. I took photos of three of the nymphs that I collected this morning: two were fairly mature, the other still small.
And where do I find this Isoperla? In the small headwater streams in Sugar Hollow. I've never seen it anywhere else. And, there was no place else that I could go to this morning. We had 3-4 inches of rain this week, and all of our streams are running high and off-color. Even this stream -- and I was up pretty high -- was as high and fast as I've ever seen it, but the water was clear.
Pretty special spot. I worked my way up close to that waterfall -- while I kept an eye out for bears! Plenty of them around at this time of year in these mountains.
Other findings this morning --
1. I also saw a lot of Isoperla holochlora Perlodid stoneflies: it's their time of year.
2. And of course I saw some spiny crawlers. This one was E. dorothea (male).
3. And to my surprise, there are still some Uenoids at this elevation that have not yet entered pupation. This one turned out to be Neophylax mitchelli.
(Can't say that I'm very pleased with those photos.)
What I did not find this morning is another Isoperla I've seen in this stream -- a real beauty --another Isoperla that Beaty says at the moment can't be ID'd to the level of species. I have a feeling that these nymphs are not all that common. I've only seen two in three seasons of looking.
Maybe next time.