Thursday, March 31, 2011
(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.
Tuesday, March 29, 2011
The development traced in this entry is that of the large winter stonefly -- family: Taeniopterygidae, genus Taeniopteryx , and the photo above shows a mature nymph -- probably 1/2" to 3/4" in length-- next to a "beginner" that was found at the end of October last year. As with the mayflies we've viewed, we will see that as this stonefly grows and matures, it becomes darker, the wingpads lengthen, and the pattern becomes richer and more complex. This is the large winter genus with "telescoping coxal gills," and as small as that little guy in the picture above was on October 23rd (Buck Mt. Creek), the coxal gills were very clear in a microscope view, and probably could have been seen with a loupe.
10/23: Buck Mt. Creek.
11/20: Rapidan River. What I'd call a "teenager". The colors are much more pronounced, the light colored stripe that runs the length of the body is very clear, and the wingpads are starting to edge off to the sides.
12/8/11: Not sure of the stream but probably Buck Mt. Creek. The bottom nymph is fairly mature; the upper nymph is well on its way -- but note how much less the wingpads are extended in the nymph at the top. Both nymphs were found on the same day in the same leaf pack.
2/15/11: North Fork of the Moormans. The coxal gills are so obvious now that they can be seen with the naked eye.
2/20/11: Doyles River. This one is almost fully mature. All that remains is for the wingpads to darken.
For the final photo, I do not have a date or provenance, and unfortunately, it's a microscope photo. But note how black the wingpads have become. This one is ready to hatch. We see very few Taeniopteryx large winter stoneflies in the streams past the end of February.
In the next entry, I will look at Strophopteryx large winter stones.
Monday, March 28, 2011
I like to start with a "dramatic" photo whenever possible -- and this one's pretty dramatic. I wish I had drawn back a little so the reader could see the length of its tails. With the tails, this nymph was probably at least 1 1/2" long. Flatheaded mayfly: genus Maccaffertium (formerly Stenonema). This was the only "Mac" that I saw here today -- I did see a lot of flatheads that were genus Epeorus.
I urge the reader to look at my last report from the Powells: 2/14/11. I had a microscope shot of some tiny Isoperla Perlodid stoneflies; I only found one or two. Today, that was the "bug of the day". I've never seen so many Isoperla Perlodids in one small part of a stream: they were all crawling around in the leaf packs. A couple of photos: the colors and wingpads show these are already pretty advanced in their growth.
I also saw some Diploperla Perlodids: I had seen a number of them here in the winter, and I thought they might all be gone -- but not so.
When I had the nymphs in my dish for photos, the two different Perlodids lined up side-by-side. The focus on the shot that I got isn't perfect -- but it's a rare chance to see how different Perlodid genera can be.
I only found one caddisfly -- a common netspinner, genus Hydropsyche -- but I managed a few good photos of it. We expect this taxon and this genus to be dark green: not always the case. A good look on the second shot of the netspinner's "anal claws," and the third shot gives us a great view of the "fuzzy belly" (Rose Brown) -- the tufts of gills on the abdomen.
I also found quite a few small spiny crawlers (all genus Ephemerella) -- too small to get any live shots. But if you look at the post from 2/14, you'll see that then I found a REALLY small spiny crawler at Powells: at least today I could tell what these nymphs were without the use of my scope.
But, I had one very small insect that I had to bring home to ID. It turned out to be my first Nemourid, genus Amphinemura, of the season! We'll be seeing increasing numbers of these in our streams through April and May, and I can get some good live shots then. This is the Nemourid with the frilly gills on both sides of its neck. I've got a microscope shot that I took of this Nemourid -- but it's not very good. Still, for what it's worth here it is. This was probably 1/8" long.
If you look REAL close, you can make out the gills at the neck.
Sunday, March 27, 2011
The small minnow mayfly nymph eventually looks like this: the "Blue-winged Olive," a favorite of fly fishermen both in the spring and the fall.
This is a continuation of the previous entry, and what I said there holds true here as well: the small minnow nymph becomes darker as it grows and matures, the patterns on it are richer, and the wingpads become longer. And although they start out almost transparent, they turn black as the nymph gets ready to hatch.
In my introduction to "The small minnow mayfly," (1/2/11), I noted that I've seen, to date, three different genera of this nymph in our streams: Baetis, Heterocloeon, and Acentrella. All of the small minnows I've seen this winter have been genus Baetis -- the "two-tailers" not the "three-tailers". And here are some of the pictures I've taken, documenting the changes that they go through. Unfortunately, my documentation is not as complete here as it was for the Epeorus genus of the flatheaded mayfly and does not cover as long a period of time. I'm quite sure I missed the earliest stages, when the nymphs first emerged from the substrate.
1. 2/14/11: Doyles River. Note that the wingpads hardly reach to the second abdominal segment.
2. 3/1/11: Buck Mt. Creek. Wingpads are longer, but still transparent (please click on the picture to enlarge the image.)
3. 3/15/11: Lynch River. The wingpads are black -- probably meaning this insect is close to hatching.
The wingpads reach to the third abdominal segment.
4. 3/15/11: Lynch River. A totally black small minnow. I suspect that this is a different species than the one pictured above -- but such a determination is beyond my level of expertise. Still -- a beautiful nymph!
In the photo above, we see a flatheaded mayfly (genus Epeorus) that is approaching the end of its "aquatic" career, while the spiny crawler (genus Ephemerella) beside it will nearly triple in size in the coming months.
In the photos I've taken in the last 2-3 months, I've been able to capture shots of a couple of mayflies at various stages as they've grown and matured, and in this entry I thought I might put together a kind of "photo history" of the development of the Epeorus flatheaded mayfly. I won't make a lot of comments: the reader can reach his or her own conclusions. I will note the dates on which the photos were taken and the location -- if I can remember! But dates should be understood as no more than guidelines.
Mayfly nymphs grow and develop at different times in different streams -- even in different spots in the same streams. And, they're individuals -- that is to say, when I lift a rock in a stream and see 8-10 flatheads, chances are good there will be babies and toddlers and teens and adults scurrying about all together: they don't all mature and fly off at the same time.
All of those caveats noted -- the most obvious changes you'll see are 1) as they mature, the nymphs become darker, with colors and patterns enriched, and 2) the wingpads get longer and longer and go from being virtually transparent in the beginning to black as they get ready to hatch. I've pointed out the "tips" of the wingpads in each of the photos. (The reader is encouraged to "click" on each photo to enlarge it.)
Flatheaded mayflies: genus Epeorus (probably Epeorus pleuralis), "Quill Gordons" to the fly fishermen.
1. 1/2/11: North Fork of the Moormans. For a microscope photo of an even smaller nymph I collected that day side-by-side with a preserved mature nymph from last year, see the entry for 1/2/11.
2) 2/15/11: not sure of the site.
3) 2/20/11: Doyles River near White Hall, VA. (Note how the gills have darkened, and the pattern is more pronounced.)
4. 3/15/11: Lynch River. (Wingpads are longer and darker -- but still not black.)
5. 3/25/11: Rapidan River. This one's ready to hatch.
I'll follow this up with an entry on small minnow mayflies.
Friday, March 25, 2011
I think that "color" is the word for the day, beginning with this brilliantly colored and wonderfully patterned Perlodid stonefly -- genus Yugus. This is the first time I've seen this genus: what a beauty!
The find was unexpected: this is a genus I did not know we had in our streams. Another look:
(The reddish orange marks at the base of the wingpads, by the way, are eggs that are stuck to the body.
Was he in the process of eating them?)
Once again, I lamented the fact that the Rapidan River is not in our watershed -- it flows through Madison County and empties into the Rappahannock. The headwaters are in the Shenandoah National Park, and I like looking for bugs near the spot where fly fisherman park to head up the stream. The insects are abundant, and they're the insects that live in high quality water. The Yugus Perlodid has a TV of "0".
This is the only Yugus Perlodid I saw today, but I saw a lot of Isoperla Perlodids and one Diploperla Perlodid. I also saw Giant stoneflies and Roach-like stoneflies and Common stoneflies -- genus Paragnetina. This is the only stream in which I see this Perlid (common) genus, and it too is a very colorful nymph as this photo reveals.
The Isoperla Perlodids surprised me: they were bigger here -- more mature -- than any I've seen to date in other streams. In this one, the wingpads are almost fully developed, and the brown stripes that run down the abdomen are already distinct. I don't expect to see Isoperlas with their colors this marked until late April or May.
I saw four different families of mayflies: spiny crawlers, brushleggeds, flatheads (all Epeorus by genus), and pronggilleds. The spiny crawlers I saw were all Ephemerella by genus -- but there were a couple of the very large, beautifully colored spinys that I've seen in this spot before. The rest were all on the small side, but still nicely patterned. Here are both types for contrast.
This spiny is in full "defensive" position -- you can see that another stonefly had just passed it by -- and it's "wingpads" are starting to look a whole lot like wings!
The river was loaded with Epeorus flatheaded mayflies, and a lot of them were also very big -- clearly getting ready to hatch. As with small minnow mayflies, when flatheads approach hatching stage, they darken in color and the wingpads turn black. Fly fishermen can expect to see "Quill Gordons" (our name for Epeorus nymphs and adults) up here in the very near future.
I had another "first" today, in addition to finding that gorgeous Perlodid stonefly. I found my first "Net-winged midges" (family: Blephariceridae) of the year. I've been expecting to see them. In the streams that I've sampled with StreamWatch, they are regulars in Buck Mt. Creek and the Doyles. This is a midge with a very low tolerance value ("0"), and for some reason they like to hang out with black flies! Go figure. They are invariably close to, or mixed together with, maturing black fly larvae. They are "scrapers" (sc) in terms of functional feeding group and "clingers" (cl) in terms of "habit". They cling to rocks that they're scraping with little "suckers" that are found on the bottom of the head and each abdominal segment. Here are the best live shots I could get (they're pretty small) -- first dorsal, then ventral.
I'll close this report with one more look at that Perlodid stonefly: finding that was an experience I won't soon forget -- and it probably won't be very long before I return to this wonderful river.
Thursday, March 24, 2011
In the entry I posted on 3/17 ("Another Secret Stream"), I suggested that the stonefly above was a large winter stonefly, genus Taenionema -- a genus I had not ID'd before in our streams. In this entry, I would like to make a detailed argument on behalf of that view.
When I first started lab work at StreamWatch with Rose Brown, on occasion we had what we were sure were large winter stoneflies, but we couldn't ID the genus. They clearly were not Taeniopteryx winters: they didn't look anything like them, i.e. like this:
And, they lacked "coxal gills," the defining characteristic of that particular genus.
But they also were not Strophopteryx nymphs: again they did not look the part, i.e. they did not look like this:
They lacked the "mottled" head, pronotum, and wingpads and the distinct "banding" on the abdominal gills: they also lacked the "triangular, ventroapical plate" that is characteristic of all large winter genera with the exception of Taeniopterx.
We set them aside. But eventually we decided that they must belong to the Nemouridae family of stoneflies since the tarsal segments on their legs were uneven in length. (As in the photo below.)
Now let me return to the present. Because I do think we have a third large winter genus, i.e. the nymph I found last week in two different places: 1) a "secret" tributary to the Moormans, and 2) Whippoorwill
Branch of the Mechum River.
Let me make my case by beginning with another look at that insect.
When I first saw this nymph in my tray last week, I was sure that it must be some kind of Nemourid, again because it looked nothing like the two large winters I knew: Taeniopteryx and Strophopteryx (should be clear from the photos above). But when I took a microscope look at this specimen, I realized that there was a problem with a Nemourid identification. 1) The tarsal segments on the legs of this nymph are equal in length = large winter stonefly:
and 2) this nymph does have a "triangular ventroapical plate."
So, off I went to my keys: 1) Barbara Peckarsky's Freshwater Macroinvertebrates of Northeastern North America, pp. 66-67, and Stewart and Stark's Nymphs of North American Stonefly Genera (Plecoptera), pp. 235-241. Based on the lack of "long dorsal hairs" on the "proximal cercal segments" (Peckarsky, p. 67) -- which we can see in the picture above -- this nymph had to be either Taenionema or Strophopteryx -- those are the only two choices. I went with Taenionema based on the color.
Let me read you what Stewart and Stark say about Taenionema nymphs: "Body 6.5-11mm, brown with darker brown mottlings on head and thorax." Now let me read you the choices Peckarsky provides:
Body dark brown, pattern indistinct; legs uniformly dark brown .... Taenionema
Body light brown or yellow, with distinct darker pattern on head and thorax; abdomen distincty banded.... Strophopteryx
Still, I wanted confirmation of my conclusion. So, I asked Billy van Wart with VA DEQ to look at the arguments I had made in my blog. (Let me quickly point out that Billy had only my photos to go on, and clearly he is in no way responsible for the validity of the determination I made.) He pointed out that the photo I had done of the "apical plate" and the "cercal segments" was inconclusive: Strophopteryx nymphs look exactly the same from the side. Sure enough -- this is a lateral view of a Strophopteryx plate.
He sent me back to Stewart and Stark to look at the "front on" view of the "ventroapical plate": these are on p. 237 for Strophopteryx (10.8 G and H), and p. 240 for Taenionema (10.10 G and H). The Strophopteryx plate narrows down and comes to a point: the Taenionema plate stays wide and rounded.
Here's a photo I just did of a Strophopteryx plate, front on:
And here's a look at the apical plate from the nymph I found last week:
I think the case is made for identifying these nymphs as large winter stoneflies, genus Taenionema.
So, why haven't we seen this genus before? Could it have something to do with habitat? Both of the streams in which these nymphs were found were small, narrow, clean water streams. Could that be a relevant factor? I suspect that it is.
I realize this entry will seem like "overkill" to a lot of my readers. But this is important to me, and I'm afraid the scholar inside sometimes takes over!