Stream Report: Powells Creek near Crozet

Our rivers continue to run very high after heavy rains on Tuesday.  And with more rain expected tomorrow, I thought I'd better get out today to see what I could find. I've had to to stick to small streams this week-- so I thought I'd go back to the Powells.  The water was high and fast here as well: still, I was able to find lots of insects without looking real hard.

The Powells at the moment is loaded with Perlodid stoneflies, genus Isoperla (as in the photo above).
I knew that, and one of my goals today was to get a really good photo of that genus of nymph.  I'd call this one "so-so".  I always want all parts of the nymph in really sharp focus.  I'll have to return and try again early in May.  (Note:  I'm still not sure of the species of this Isoperla.  The photos look very much like Isoperla montana, but it's not safe to rely on photos alone.)

Lots of stoneflies again in the leaf packs.  Literally dozens of Isoperlas in one big pack of leaves -- but I also found Eccoptura Common stoneflies, a few Diploperla Perlodids (fully mature wingpads -- ready to hatch), and a couple of tiny Nemourids (genus Amphinemura).  This genus of Nemourid is tiny to begin with, and when they're still in early instars, they're very difficult to shoot with the camera, even with a good macro lens at full magnification.  Here's the best I could do.  (Don't forget to click on all photos to enlarge them for better viewing.)

At least this one was big enough to allow us to make out the "cervical gills" at the neck.

Mayflies?  I saw a few flatheaded mayflies, all still Epeorus, and a couple of small spiny crawlers.
That's about all I can report for today.  But let me show you the nice photos I got of the Eccoptura stonefly and the Diploperla Perlodid.

Eccoptura common stonefly (Perlid):

Diploperla Perlodid:

The Treasure Hunt -- Finding Another Gem

A friend of mine compared my looking for insects to a "treasure hunt" -- pretty well said.  I never know what I will find, but whatever it is, it's bound to result in some beautiful pictures, and every so often I get a surprise -- something totally new!  This time -- not a new "genus" of Perlodid stonefly, but a new "species".   This is a Perlodid stonefly, genus Isoperla, species similis.  I've never seen one before, and I never would have guessed this was a new Isoperla.  Every Isoperla Perlodid that I've seen before in our streams had brown stripes running the length of the abdomen -- which is a defining feature for most species of Isoperla -- but not all.   When I got home and keyed this out to Isoperla, I went to some internet sites for confirmation.  Sure enough -- Isoperla similis (two sites you might want to look at: 1) http://bugguide.net/node/view/20605/bgimage?from=24, and 2) http://www.pbase.com/tmurray74/image/110648194).  I did find a "normal" Isoperla (I think it's Isoperla frisoni or Isoperla bilineata) at the same site this morning (the site goes unnamed); it's to the right and behind in the photo below, a side-by-side comparison.  (The tolerance value for Isoperla similis, by the way, is ".7"; for Isoperla bilineata -- which is common in our streams -- "5.5".)

At the same site, I found a number of Green stoneflies (Chloroperlids), a common netspinner (genus Diplectrona), a few Uenoid case-maker caddis, some prong-gilled mayflies, flatheaded mayflies (genus Epeorus and Leucrocuta), a rolled-winged stonefly (Leuctridae), and one lonely Ameletid mayfly.  Finally, I found a "pupating" caddis.  When I put its little rock "dome" on its back, the cocoon was easily seen.

I suspect this was a common netspinner pupa: to be sure, I'd have had to take it back home, open up the cocoon, and look at the developing pupa under the scope.  I decided to return it to the stream.


On my way back to town from this adventure, I decided to have a look in the Whippoorwill Branch of the Mechum.  It is absolutely "lousy" with spiny crawler mayflies.  This is common for this time of year, and I'm sure the StreamWatch volunteers are running into large numbers of them in the streams that they sample.  In the photo below, I got a good picture of a spiny crawler "crawling" over a stonefly (common stonefly, genus Eccoptura).

If you want to go out looking for "spinys" and not work very hard, turn over rocks that are covered with moss (well, I don't know my grasses, so I doubt that it's "moss," but it's moss to me).  Lift the rock out of the water and wait a few seconds.  They'll start moving out of every blade of grass you can see!
I lifted some rocks today that easily had 40-50 nymphs moving around in that vegetation.

One final look at our "catch of the day": Perlodid stonefly, Isoperla similis.

Question: What's the Reason for "Colorful" Nymphs?

                                                (Perlodid stonefly: genus Yugus)

                                       (Spiny Crawler mayfly: genus Ephemerella)

                                         (Perlodid stonefly: genus Helopicus)

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Three examples will suffice.  Question: why have some mayfly and stonefly nymphs evolved with beautiful, colorful, patterns and colors?  We're used to seeing this in insects, birds, and mammals when they're ready to mate -- especially in males.  This has nothing to do with mating.  In fact, I believe I'm right in saying that mayfly and stonefly nymphs lack sexual organs in this stage of development: genitalia only appear with the transformation into terrestrial adults.  And as adults, many of these "beautiful" nymphs are drab in appearance.  If anything, being colorful and richly patterned in the nymph stage would seem to be a bit risky: it makes them more obvious to predators -- mainly fish.  And trust me they're "obvious": I know where I've found them, and this has nothing to do with "camouflage".

Can anyone out there explain this?

The Doyles River in Spring and the Question of "Protocol"

                                                 (Perlodid stonefly: genus Helopicus)

When I first found this genus of Perlodid stonefly two weeks ago in Buck Mt. Creek (post, 4/2/11), I wondered if I'd see it again anywhere else.  Sure enough, I found two more in the Doyles River today.  Actually, the pair cozied up for me so I could get a group portrait.  Two different sizes: two different colors -- which I think is a matter of age (the older they get the darker they get?).

I also found a lot of Diploperla Perlodids -- the most I've ever seen at one time -- and I'd have to call these "mature".

To finish up on the stoneflies -- I found one, and only one, very small Nemourid stonefly, genus Amphinemura, the genus with the "cervical" gills sticking out on both sides of the neck.  This nymph was so small that I could not see the gills when I took this shot at the stream.  When I cropped the photo at home, there they were.  (Please click on the photo to enlarge, and please forgive me for not making this sharper -- it was a "very" small nymph.)

The actual size of this nymph was probably less than 1/4".  But they will get bigger  -- and darker -- through April and May, and by May, I expect to see a lot of them in our streams.

Mayflies?  There were still of number of Epeorus flatheaded mayflies, and lots and lots of "spiny crawlers" (family: Ephemerellidae; genus Ephemerella).   The small minnow mayflies I saw here in February in March seem to be gone -- the "Blue-winged Olives" have hatched!  Rocks often had 4-6 spiny nymphs crawling around, and I had no problem getting some pictures of nymphs of various sizes.

That the gills on spinys are "on top" of the abdominal segments and do not stick out to the sides of the abdominal segments is very clear from this picture (the gills are "tan").

The mayflies today were almost all on the bottoms of rocks; the stoneflies were all, without exception, crawling around in densely packed leaves in the stream.  This is pretty much what I've found to be true since I started this project.  This made me wonder today about the protocol used when we sample our streams.   In getting its samples, StreamWatch -- and I suspect this is true for Save Our Streams teams as well -- looks in the riffles.   But I think that's a problem in terms of getting a good sense of a stream's populations.  Stoneflies like leaf packs: it's where I've found them all year.  And leaf packs are hardly ever in riffles -- big leaf packs at least.  They're often wrapped up on limbs in the stream, or packed in behind boulders out in the current.    So are we seeing as many stoneflies as we might, if we only sample the riffles?

I don't bring this up to be critical of the StreamWatch approach: their methods are top of the line, and I know that a lot of time and thought went into the development of that protocol -- the same for VA SOS.  And, were there a "perfect" way to go about sampling, the "pros" would have found it by now.  But when I find a lot of insects -- and a lot of good insects -- in places that I know sampling teams tend to avoid, I wonder if there isn't something we're missing.

Perlodid Stoneflies: Genera in Central Virginia

I have now seen, identified, and photographed a total of 5 genera of Perlodid stoneflies in our streams.
There may be more to be found -- but in the meantime, I thought I would sum up my results and make a few other comments.

The first time this season I saw any Perlodids was in November -- they were so small, I did not attempt identification.  I found them in the Moormans River and Buck Mt. Creek.

In December, I was finding Clioperla Perlodids (as in the photo above) and in more than one stream.  I have photos I took at Mechunk Creek and Buck Mt. Creek.  And throughout the winter, this was the most common Perlodid genus I saw.  I found them -- in addition to the two streams just mentioned -- in the Lynch River and the Doyles River -- probably elsewhere, but I no longer remember.  By January, I was already seeing nymphs that were fairly mature, though the wingpads were not yet fully developed.
But the nymphs I've seen lately are fully mature -- and I suspect that this stonefly is already hatching.
In the "Tolerance Values" list that I use, North Carolina lists 1 species of Clioperla -- Clioperla clio -- which it gives a TV of 4.8.

The second genus that I saw early on in the winter was Diploperla.  (Photo below.)

My first sighting of Diploperla was in Powells Creek near Crozet (February?).  Since then, I've seen them in the Lynch River, and my "hidden stream" in Sugar Hollow (also the Doyles?).  The nymphs that I saw were fairly developed, so this genus, too, may be an "early bird":  i.e. it too may already be hatching.  But, I found some again in the Powells only last week, and they were still not fully mature.  So, I'm not sure of the length of the season for this particular genus.  North Carolina lists 3 species of Diploperla, and the TV's range from 1.5 to 2.7.

Next, Isoperla.  This is the most common genus we see in our streams, and I started to see "tiny" nymphs first in February.  By now, they are starting to mature very well -- note the wingpad development on the one in the picture above (Powells Creek, last week) -- but we'll be seeing them in large numbers throughout April and May.  North Carolina lists 12 species of Isoperlas: the TV's range from 0 to 5.6.

This was one of the surprises for me: Perlodid stonefly, genus Yugus.  I found this in the Rapidan River on March 24th.  But note that it, too, seems to be fully mature -- the colors and patterns are fully developed and the wingpads fully grown out (but not yet black?).   I doubt that there are many streams in central Virginia with this genus in them.  North Carolina lists two different species: the tolerance value is "0".

Finally, my latest find -- genus Helopicus.  This is from Buck Mt. Creek where I found a number of nymphs on Saturday -- April 2nd.  I have not yet seen it anywhere else -- but I'll be looking!  North Carolina lists 2 species of this particular genus: the tolerance values are "0" and ".8".

Fly fishermen get excited about only one of these genera -- Isoperla.  Isoperla Perlodids hatch as "Yellow Sallies," typically from July to September out West.  It would be nice to know more about all Perlodid genera in terms of life cycles and know when they first appear in our streams -- what month of the year -- and when they fly off as adults.  So many projects -- so little time.
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(Added 6/4/11:  A sixth genus: Remenus.  Found at Buck Mt. Creek on 5/31 and at a tributary of the Moormans on 6/1.  See the entries posted for both of those days.

Buck Mt. Creek: Perlodid stonefly -- genus Helopicus

Another week, another new Perlodid stonefly genus -- or so it seems.  This is genus Helopicus, and this is the first time I've seen it (well, the first time I've known that I've seen it!)

It was a sunny day when I set out for Buck Mt. Creek.  But as soon as I found some insects for photos  it clouded up, and I thought the day was a loss.  I had found lots of small minnow mayflies, a few small spiny crawlers, an Epeorus flatheaded mayfly, and lots of very big black flies.   The clouds made it impossible to get any good shots.

So I headed back to the car.   But there was a riffle on the way back to the car in which I had found lots of insects before, so I decided -- if the sun comes out, I'll stop and see what I can find.  The sun came out -- and I found the same insects I had found in the first riffle, some "Net-winged midges" mixed in with the black flies -- but, three beautiful stoneflies.  As I took some photos, I realized these were Perlodid stoneflies, not "common stoneflies" (Perlids), and that this was a genus I had not seen before.  So I preserved a few and headed home to my lab.

When I keyed this out, I came to a choice between the genera Yugus or Diura.  This was based on the fact that there is a "knob" below the second lacinial tooth.  (In the photo below,  the nymph is turned on its side, and this is the underside of the head.  Laciniae are part of the maxillae -- jaws.)

But, Diura is not a genus that is found in Virginia, and I had found a Yugus last week, and this nymph did not accord with the morphological features that are found in that genus (see Stewart and Stark, Nymphs of North American Stonefly Genera (Plecoptera), p. 455).  Below -- Perlodid stonefly, genus Yugus -- note the completely different pattern on the head.)

When I looked at pictures of Perlodid stoneflies on "Bugguide.net," the only thing I saw that resembled the nymph I had found was genus Helopicus -- a Perlodid stonefly with a "head with a transverse brown band between [the] antennae" (Steward and Stark, p. 397.)   But, all the keys say that Helopicus Perlodid stoneflies have "submental gills."

Back to the microscope.  When I lifted the head and looked carefully below the chin at the top of the neck -- sure enough, there were submental gills, fingerlike projections that stick out from the submentum that are "twice as long as the greatest width" (Peckarsky, et.al., Freshwater Macroinvertebrates of Northeastern North America, p. 71.)

I had found what for me was a new genus of Perlodid stonefly: the gills, along with the "dark transverse band between the eyes" (Peckarsky, p. 71) give us Helopicus.  Another look at this beautiful creature.  (Should we think of it as the "Lone Ranger" of Perlodid stoneflies?!  Sure looks to me like it's wearing a mask.)

This is exciting: I love finding new things.   I worry about what I will do when there are no new genera to find (may never happen).   Then I'd have to move west to find the variety that I've come to enjoy!

Stoneflies: Pictures of How They Change, Pt. II. -- Large Winters

                  (Large winter stonefly adults: North Fork of the Moormans, April 12, 2010.)

This is the last entry I'll post in this series -- showing photos that illustrate how nymphs change as they grow and mature -- it is also the last "new"material I'll add to the blog for a week -- I'll be on a mini-vacation next week.   For new entries, please check back next weekend -- April 9-10.

 Our focus here is the large winter stonefly, genus Strophopteryx.  The changes you'll see in this sequence of photos pretty much follow the track that we've seen -- as the nymphs mature, they become darker in color, the patterns enriched, and the wingpads get longer.  There is one change.  Strophopteryx nymphs come in two colors: most that we see are yellow and green, but some are brown and orange.  In the pre-hatch stage, the wingpads of the yellow/green nymphs get lighter not darker; they look "tan" when the nymph is in water.  The wingpads of the brown/orange nymphs, on the other hand, follow the normal pattern we've seen of turning dark brown or black when the insect is ready to hatch.

12/11/10: Buck Mt. Creek.  This was the first sighting I had of this genus this season.  The nymphs I picked up that day were small, so my photo has to be a microscope shot.  Note that the "base" color is yellow: the head, prothorax, and wingpads are "mottled" with olive green and brown spots; the abdomen has alternate stripes of yellow and green.  (Strophopteryx nymphs, by the way, almost always "curl up," in this fashion when they're put into alcohol vials -- maybe we would too!)

12/28/10: Buck Mt. Creek.  Not the best of photos -- but good enough to make the point.  The wingpads are starting to lengthen and the colors are starting to darken.

1/6/11: Buck Mt. Creek.

1/25/11: Buck Mt. Creek.  The body is darker with the abdominal stripes -- in this photo at least -- somewhat muted in color.  But note how the wingpads are longer and wider than those on the nymphs in the previous pictures.

2/7/11: Buck Mt. Creek.  A rare shot of a nymph on a rock.  When I turned this rock over, there were 5-6 nymphs moving around.  I'm surprised that this shot turned out as well as it did given the low light conditions.  Please click on the photo to enlarge to see how the wingpads are changing.

2/14/11: Doyles River.   I'd call this nymph fairly mature.  The wingpads might get a little bit lighter, but otherwise it's fully developed.

2/14/11: Doyles River.  In the same stream, possibly on the same rock (I can't remember), I found the brown/orange version.  This was the first time I had seen this color scheme: beautiful!  And note that the wingpads are dark.

3/1/11: Buck Mt. Creek.  One final shot -- though I'm not sure this is a lot different than the nymph above found on 2/14.  I do remember the wingpads on this nymph being "tan": somehow that did not come out as well as I had hoped in the photo.