Searching for Isoperla Perlodids at Buck Mt. Creek

I had high hopes this morning as I drove out to Buck Mt. Creek.  It's Isoperla time in our part of Virginia, and Buck Mt. Creek is rich in this type of stonefly.   But you need to find leaf packs to find Isoperlas, and most of those were washed away in the high water that we had last week.  Nonetheless, I did locate a mixture of leaves and sticks by the side of the stream, where I met with success.  The photos I got are not up to my standards -- the clouds arrived with me -- but we take what we can get.

Perlodid stonefly, Isoperla dicala.  It's one that -- to date -- I've only seen in Buck Mt. Creek and the Rapidan River.   Since I've identified this one before -- on 5/1/1/12 and 4/13/13 -- I won't go into detail.  But, the key patterns are easy to see.

"pale marks anterior to median ocellus sometimes indistinct, sometimes with darker border."  (Steven Beaty, "The Plecoptera of North Carolina," p. 23)  On the nymphs that I found, the pale marks were very distinct, and yes, they did have dark borders.

The other feature to note: "dark longitudinal abdominal stripes with very narrow pale borders." (Beaty, p. 23)  You can see the pale borders in the live photos, but they're easier to see in this microscope view.

In North Carolina, this species is not assigned a tolerance value which means there's not enough data to use.   They were plentiful today in Buck Mt. Creek.

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I found only one additional species of Isoperla, the one that I've labeled Isoperla nr. orata.  But the photos I took were not something that I want to post.  Here's a shot from last year so you'll know which nymph I mean.

I've sent Beaty some specimens to see if he has any thoughts about the ID.
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Two more pics from today.  The first, a "long-horned" caddisfly larva, Ceraclea maculata.  In the photo, you can see its head peaking out at the top of the case.  I found one two years ago in this very stream in the very same riffle.  For a full discussion of the ID -- and some much better pictures -- please see the entry from 5/6/13.

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And the second, a flatheaded mayfly, genus Rhithrogena.  Hope to work on the species ID later on, though species ID of Rhithrogena is still up in the air.

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Not the best of days.  With sunlight it would have been fine (and of course the sun came out when I headed home!).  But on Thursday, I'm off to the Rapidan River where I expect to see Isoperla species galore.

The Perlodid stonefly Remenus bilobatus in a stream where I've not seen it before

As you will see in a minute, it was one of those days when the pictures I took of the stream (small stream in Sugar Hollow) were better than those that I took of the insects.  But... first things first.

This is a Perlodid stonefly, Remenus bilobatus, one that I don't see very often.  Before this, I've only seen it in Buck Mt. Creek and the Rapidan River.  It is not a very colorful insect: "habitus brown, without conspicuous markings" (Beaty, "The Plecoptera of North Carolina," p. 26).  Though, like all of our stoneflies, they look better and better as they mature.  The photo below was taken on 5/24/13 at the Rapidan River.

But with a Tolerance Value of 0.9, there's no reason it shouldn't be found in these small mountain streams.  This is the stream that I went to today.

Remenus is a genus that has a feature that's very distinct: the lacinia has only one tooth.  Easy to see in this microscope photo.

But there's another feature that allows us to know what it is with just from a look through the camera: the bases of the maxillary palpi stick out from the side of the head, beyond the lateral edges of the eyes.

It's one of the last Perlodids to appear in our streams, and right on cue, I normally find it in May and June.
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I only photographed one other insect,a young Isoperla that, like Remenus, is a late bloomer appearing in April through June -- Isoperla holochlora.  We'll see a lot of them later this month: it's fairly common in the streams that I visit.

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Not the best photos, not the best of conditions.  It was hot and humid -- as you can see from the condensation on the base of my dish -- and the sunshine was a little bit hazy.

But what a stream to explore!

Drunella doddsi, a big spiny crawler from the Northwest: back from Portland, OR

It was a quick trip to Portland: our daughter's a Pastry Chef, and she's swamped with work at the moment.  But we did have time to go up to the Washougal River in WA, which is not far away.   And there we found a whole lot these...

Spiny crawler mayfly, Drunella doddsi.  Took me a while to identify this, the but key to use -- as always -- is Roger Rohrbeck's "Pacific Northwest Mayflies" at the following site: http://www.flyfishingentomology.com/PNW%20Mayflies.htm.   There we find the following description of doddsi:

Body flattened; abdomen yellowish brown, w/o tubercles; thorax often lighter; head w/incomplete frontal shelf; ring of fine hairs encircling underside of abdomen; gills of similar size starting on seg. 3 ..

Body: reddish to dark olive brown. Wings: medium gray. Length: 13 mm. Tails: 3.   Emergence: Jul 10-30.

1. I'd say the color's right on -- more "reddish brown" than anything else.  The size of our nymph -- and it was fairly mature -- was exactly 13 mm.

2. There were no tubercles on the abdominal segments, contrary to most other species of this particular genus.  Were they present, they'd be on the posterior edge of some or all of the segments.

3.  The frontal shelf is clear in the live photos I took.  Here's a microscope view.  Also note the tubercles on the leading edge of the fore femora, one of the keys to the Drunella ID.

For a "complete" frontal shelf, we can look at a Timpanoga hecuba nymph.   (Montana, Blackfoot River, August, 2013.)

4.  There is indeed a "ring of fine hairs encircling [the] underside of [the] abdomen."

5.  And we can see the size of the gills, and the fact that they start on segment 3, in the second photo above.

Drunella doddsi:  slated to hatch as the "Western Green Drake" in June or July.  Given the number of nymphs that I saw on the rocks, there'll be a heck of a hatch on the Washougal!

(Now, I have to find out what this little nymph is.  I've been calling it Drunella doddsi -- apparently by mistake.  It's very small, and I've seen it in Oregon and Montana in August.  Hmm...

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2.  Also found one of the stoneflies I've seen on a number of trips to Oregon and Montana: the common stonefly, Calineuria californica.

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3. But the river was loaded with cases made by the "October caddis"  -- a Northern case-maker, genus Dicosmoecus.   When I was out here last year, I found a number of cases, the kind that are made by larvae that are still immature ( "The mature larva makes a long, tubular case out of pebbles [~ 30 mm] the immature larva makes a case out of a mixture of pebbles and sticks to which is attached pine needles.")   (For this description of cases, see the article by Michael P. Limm and Mary E. Power, cited in my entry of 5/1/14.)

For the genus ID, see the description provided by Wiggins in the same entry (5/1/14).  On the species -- I speculated last year that the larvae I found were Dicosmoecus gilvipes.  This year -- having found larvae that are more mature -- I could easily see what we needed to see to nail down the species ID.  There are only two choices: atripes and gilvipes.  Both have a fringe of sharp spines on the front edge of the pronotum.  But on the head, atripes has "miniscule spines," gilvipes does not -- it's "bald."  Clearly we've found gilvipes.

The Washougal was loaded with cases of D. gilvipes.   They were all over the rocks in the slow water on the sides of the river: had to be careful where you put down your feet.  But, I found immature cases, cases somewhat in "transition," and cases that were those made by larvae that are already fully mature (long, tubular, made out of pebbles).  Some photos of some of each.  (Not my best photos.  I had the ISO set too high, and I lost sharp definition.)

1. case made by an immature larva

2. both immature and mature

3. a case in "transition": the front has been changed over to pebbles; the rear is still sticks and needles.

And one of the more interesting cases I've seen.  About half way back from the front, it divides into two parts.

That's the view from above: in these photos, the case is turned on its side.

(I've not yet identified the flatheaded nymph that's perched on top of the case.)
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All in all, a pretty good find, and it sure was a nice place to work.

Well, my original ID was right! It's Maccaffertium pudicum

We learn by making mistakes: or so it sometimes seems.  After careful study of our flatheaded nymph from the Rapidan River -- and a little help from some friends (Steven Beaty, Jessica Fang) -- I find that my original entry was right.  This is Maccaffertium pudicum, Tolerance value -- as it should be for this river -- 2.1.

Here's what I discovered.

1) I remeasured the nymph: it is indeed 11 mm.  M. pudicum nymphs are 11-14 mm.

2) I was wrong about there being "denticles" on the protarsal claw.  What I had pointed to in the photo in my previous entry was a "basal tarsal claw," not a tooth.  There are no denticles on the protarsal claw of M. pudicum nymphs.

3) M. pudicum has posterolateral projections on segments 3-9.  Here's a better photo of that (I removed the gills on the right side), but I also see a projection on 2.  Also relevant to the ID, the projection on 9 is shorter than that on 8.  (See p. 33 in Bednarik and McCafferty.)

4) There are 30-40 lateral setae on the maxilla.  Tough to see all of them in my photo, but I count at least 31.  [For this data, see p. 14 in Philip A. Lewis, "Taxonomy and Ecology of Stenonema Mayflies,"  published by the National Environmental Research Center in November, 1974, in the Environmental Monitoring Series.  (Stenonema was changed to Maccaffertium for all but one species in 1979.]

5) While I can only see, using my microscope, 8 setae on the maxillary crown, pudicum should have 15-40.  I've already noted that there might well be more setae on the crown than I can see.

6) And the real key, for me, in establishing that this is a pudicum nymph, is that the ventral pattern is an exact match for one of the two patterns that we should see on pudicum nymphs: notice the splotches on 6-8, the largest/darkest being on 7, and the oblique anteromedial lines.

This illustration is found in Unzicker and Carlson's "Ephemeroptera," p. 3.75, figure 3.214.  Their essay is Chapter 3 in Aquatic Insects and Oligochaetes of North and South Carolina, edited by Brigham, Brigham, and Gnilka.  This illustration was originally published in A.F. Bednarik and W.P. McCafferty, "Biosystematic Revision of the Genus Stenonema", Canadian Bulletin of Fisheries and Aquatic Sciences, 201 (1979), p. 69, figure 78.  Their description (p. 33) reads as follows: "Sterna 4-8 mostly pale with brown markings varying from faint submedian dots and oblique dashes near anterior margins to median broad brown areas near anterior margins (fig. 78); 7 and 8 sometimes with brown maculation expanded to cover much of anterior parts of segments (fig. 79); 9 with brown lateral bands often connected or nearly so by brown cross band on anterior of sternum." (I've underlined a key phrase.)
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I've certainly spent more time on this nymph than I ever intended -- but I've learned a lot about the anatomy of mayflies.  Glad I was wrong in my last entry.  Oh, I should add that all sources say that M. pudicum nymphs hatch from April through September.  So this one was right on time!

Heading to Oregon on Thursday.  Very excited.  Get to see totally different stonefly, mayfly, and caddisfly species.
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It was NOT Maccaffertium pudicum: M. mediopunctatum? M. wudigeum?

Back to the drawing board on this one, this beautiful, fully mature flatheaded mayfly from the Rapidan River.    It was not Maccaffertium pudicum.  The problem is, using Beaty's "Ephemeroptera of North Carolina" (version 4), I can't really determine the ID for sure.  I'm hopeful that he'll take a look if I send the nymph to him in a vial.

Having looked carefully at all of the relevant features, I've arrived at two possibilities: M. mediopunctatum and M. wudigeum.  Let me show you how I got there.

1. The nymph, and it's fully mature, is 10 mm long -- tops.  Of the 15 species that Beaty describes, that feature alone eliminates all but the following:

M. exigum
M. ithaca
M. medipunctatum
M. meririvulanum
M. modestum
M. sinclari
M. terminatum
M. vicarium
M. wudigeum

 2. Another key feature in Mac ID is the presence or absence of denticles on the protarsal claw (claw on the first leg).  They are present on this nymph.  Two photos.

Of the species noted above, only 5 do have -- or "may" have -- those denticles.

M. exigum
M. mediopunctatum
M. modestum
M. terminatum
M. wudigeum

3. And another key feature -- the presence or absence of posterolateral projections on abdominal segments anterior to segment 6.  They are present on our nymph.

That leaves us with only two possible species ID's: M. mediopunctatum and M. wudigeum.
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Beaty's species descriptions read as follows.

M. mediopunctatum -- nymphs 7-10 mm; 0-9 (usually 5) hairs and 4-8 (usually 5-6) spine-like setae on maxillary crown; protarsal claws usually with denticles; posterolateral projections present anterior to segment 6; sternal maculations variable though usually with dark crossbands on sterna 2-8 and 9 with dark, obliquely oriented lateral bands, sometimes connected anteromedially.  A facultative summer species only found in the mountains, especially rivers.  (Beaty, p. 34)

     [Note: Beaty's earlier description of M. mediopunctatum (version 3.3) differs in one significant            way.  It ends: "sternal maculations variable though usually with dark crossbands on sterna 2-8,        and 9 with dark, inverted "U".   (p. 19)   I've put the key words in Bold.]

On the hairs and spines on the crown -- I can see 8 hairs and 5 spines.  (But the hairs are very difficult to see, and therefore to count.  There might be smaller hairs that I can't detect with my microscope.)

On the sternal maculations -- I could be convinced that there are "obliquely oriented lateral bands" on segments 1-9.  (Note the little red arrows.)

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M. wudigeum -- nymphs 8-10 mm (?); no hairs and 5 spine-like setae on maxillary crown; protarsal claws with denticles; posterolateral projections present on segments 3-9; dark coloration on outside edge of pronotum, clear on extreme lateral edge; abdomen mostly brown dorsally, each segment with pair of submedian dark dots; ventrally pale.  This recently described species will key to couplet 4 in Bednarik and McCafferty (1979).  Collected from upper Wilson Creek and the lower Linville River.  Listed by NC Natural Heritage Program as Significantly Rare (2012).  (Beaty, p. 35)

Probably not as good a fit as M. mediopunctatum.  Our nymph clearly has some hairs on the maxillary crown, and I'm not sure that the pronotum looks like it should (also not sure that it doesn't!).

However, it looks to me like the anterolateral projections do indeed extend from segments 3-9, and  there do seem to be paired submedian dark dots on at least some of the abdominal terga.

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Well, that's the best I can do.  Time to consult with the master.  I'm leaning towards M. mediopunctatum.  But, I'm bothered by the last line in Beaty's description: "A facultative summer species only found in the mountains, especially rivers."  It sure isn't summer, and this nymph is already fully mature.

Stay tuned.
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