Saturday, November 26, 2011
One of the earliest Perlodid stoneflies we find in our streams -- and one of the first to mature in the new year -- is the one in the photo above: Clioperla clio (there is only one species of Clioperla). Last winter, I found a lot of them in Buck Mt. Creek. So I went there this morning hoping to start seeing some young ones. I did, but I also found three, like the one in the picture above, that were already fairly mature. I was amazed.
But according to Stewart and Stark (Nymphs of North American Stonefly Genera, p.381), this is a nymph that exhibits "fast-seasonal growth." From the growth of the nymphs that I saw last year, I'd say that this is a species that hatches mainly in March and April. I also discovered last year that Clioperla clio is an "aggressive" predator! I lost more than one small minnow mayfly to hungry Clioperlas. This is confirmed by Stewart and Stark (p. 381): "Feminella & Stewart (1986) found C. clio nymphs consistently among leaf litter throughout the year, and mature nymphs were found to be major predators of leaf pack-dwelling invertebrates." When you have some of these nymphs in your tray be careful about putting other nymphs with them.
C. clio nymphs are easy to spot because of their heads: a large area of yellow, encircled by a band of black or brown. Let me quote again from Stewart and Stark (p. 381): "Head mostly yellow with dark bands extending through or behind lateral ocelli to compound eyes and across anterior margin of frons, enclosing large yellow quadrangular area."
Anatomically, Clioperlas are put together a lot like Isoperlas. They have a very clear "Y" ridge (mesosternal), and the lacinia has two teeth at the end, followed by a series of smaller teeth or setae.
And the lacinia
From these features, Peckarsky (Freshwater Macroinvertebrates, p. 73) takes us to the following couplet:
45a. Dorsal abdominal segments with alternating transverse or longitudinal light and dark stripes or bands .... Isoperla
45b. Dorsal abdominal segments uniform, brownish except for a few small light spots (which may be in longitudinal rows).... Clioperla
No doubt about the color of those abdominal segments, and, the "light spots" are visible as well. Clioperla clio. Some more photos or this beautiful nymph.
I was also hoping to see maturing large and small winter stoneflies today. The small winters are clearly starting to color up with darker wing pads; the sole large winter stonefly I found was not much bigger than those I found here last week.
small winter (Capniidae, genus Allocapnia)
large winter (Taeniopterygidae, genus Taeniopteryx)
Oh. And I mentioned last week that Allocapnia small winter stoneflies have "truncated" rear wing pads that are often "notched". These clearly were.
One more look at the "catch of the day."
Friday, November 25, 2011
I went back to the Moormans today -- well, back to one of the small streams that feeds into the Moormans -- where I found, among other things, this immature freeliving caddisfly larva. A lot of freeliving caddisfly larvae inhabit this stream, and I've written about them before and posted photos. To refresh your memory, look back at the entries from March 4th, May 20th, and June 14th. The colors have varied: some were bright green, some were aquamarine, some light green, and some were a nice creamy white -- like the one in the photo below (this was shot on March 4th.) (Of all of the photos I've taken this year, by the way, this is probably my personal favorite.)
The most common freeliving caddis we see in our streams is bright green, with a distinct pattern on top of its head. This one.
This is the insect monitors expect to see if they see a freeliving caddis. This larva is a Rhyacophila fuscula. Let's see what Beaty has to say on this species:
"R. fuscula -- larvae large, ?? mm; long apicolateral spur; dark H-pattern on head interrupted anteriorly and extended posterolaterally; pronotum mostly dark. Most common and tolerant Rhyacophila in NC."
("The Trichoptera of North Carolina") (The tolerance value is still a mere 1.6.)
So what is the "apicolateral spur," and can we get a better look at that "H" on the head? The "apicolateral spur" is a spur that sticks out from the top (apex) of the anal proleg and parallels the anal claw. This is easy to see in a microscope photo.
The "interrupted H pattern" can be seen in the photo above, but it shows up better in this photo I took at the start of the month (November 4th, Rapidan River).
So, there is no top (front) to the "H," but the dark colors extend to the side and the rear. Rhyacophila fuscula.
But what about the larva that I found today? Clearly not Rhyacophila fuscula -- but it is a Rhyacophilid (freeliving caddisfly larva)! Here's another look at the larva, and take a look at that head and pronotum.
The head is burnt orange to brown to almost black at the front -- no "H" pattern in sight. And the body will not be bright green when the larva matures: I'd go for creamy white or aquamarine.
Does it have an "apicolateral spur" on the anal proleg? It does not, though there do seem to be "ventral teeth" on the anal claw. Take a look.
The "ventral teeth" seem to eliminate what might otherwise be a possible option -- R. carolina -- about which Beaty says: "R. carolina -- larva ?? mm; head golden brown. Second most common Rhyacophila in NC."
At the moment, I'm leaning towards R. nigrita (TV is 0.0), which lacks the apicolateral spur but does have ventral teeth on the claw. And there's another relevant feature -- the color of the pronotum.
"R. nigrita -- larva ?? mm; head black or brown and parallel sided; pronotum darker anteriorly. Occurs mostly in small Mountain streams. Third most common Rhyacophila in NC. " Take another look at the head and the pronotum.
The front edge of the pronotum is clearly darker than the rear portion. Species ID of Rhyacophila larvae will be an interest of mine throughout the winter and spring.
My other findings today were things that I would have expected: Giant stoneflies, Common stoneflies (Acroneuria abnormis and Eccoptura xanthenses), crane fly larvae (still pretty small in this stream), Peltoperlid (Roach-like) stoneflies, a few flatheaded mayflies, and, of course, lots of small winter (Capniid) and green (Chloroperlid) stoneflies. Here are some photos of the latter taxa to finish the entry.
And a "double":
(Below, one of the riffles I sampled today. I go looking for aquatic insects for the same reason that I go fishing for trout -- they live in beautiful places.)
Wednesday, November 23, 2011
I'll return to this photo -- but first things first. I have just learned from Steven Beaty (Biological Assessment Unit, North Carolina Division of Water Quality) that his "Taxonomy Documents" for North Carolina have now been published online. They can be accessed at: http://portal.ncdenr.org/web/wq/taxonmanual. Separate manuals, in pdf files, are available on 1) The Ephemeroptera of North Carolina, 2) The Plecoptera of North Carolina, 3) The Trichoptera of North Carolina, and 4) The Aquatic Coleoptera of North Carolina. This Biologist's Handbook with Standard Taxonomic Effort Levels, provides detailed keys for family, genus, and species identification of the mayflies, stoneflies, caddisflies, and aquatic beetles that are found in North Carolina.
This is an incredible achievement, and it will probably serve as a standard reference work in the field for many years to come. And, it's available for free! You can even do what I just did -- download it, print it out, and go have it bound for easy use. This is pretty special.
Now, back to the problem of species identification of Maccaffertium flatheads. Dr. Beaty had a look at some of the photos I posted just yesterday -- and thought it unlikely that those nymphs were either M. mediopunctatum or M. Meririvulanum. Why? He's quite sure that there are hairs that follow the spines on the crown of the maxilla. It looks to me like he's right. He was inclined to think -- and I won't hold him to this; that would hardly be fair -- that both nymphs were Maccaffertium pudicum in terms of the species ID.
Now (I can quote him at last!), take a look at what he says on M. pudicum nymphs. "M. pudicum -- nymphs 11-14 mm; lateral projections anterior to 6; 4-8 spines and 15-40 (usually 20-30) hairs on maxillary crown; no denticles on claws; sometimes with dark pattern on anterior edge of abdominal sterna; sterna 5-8 with anterior markings or completely pale. Mountains and Piedmont. Common in smaller streams." ("The Ephemeroptera of North Carolina," p. 20)
Take a look at the photos I posted just yesterday and see what you think. In the meantime, I decided this morning to look into the species ID of the nymph in the photo above. This one was found in a small stream near our home just south of Charlottesville on 11/11/11 (the stream where I took the photos of scuds). Before I had communicated with Dr. Beaty on the nymphs I discussed yesterday, I had reached the conclusion that the nymph in the photo above was probably Maccaffertium pudicum. The evidence: 1) this nymph (and I found three others like it) was 13mm long (BIG), and it's still not fully mature; 2) it does for sure have hair after the spines on the crown, and I can count at least 20; 3) the claws are edentate; 4) there are, for sure, posterolateral projections on all abdominal segments; and 5) there is a dark pattern on the anterior edges of at least some of the abdominal segments. Here are the photos that I took this morning.
1. Maxillary crown -- spines and hairs (I know you can't really count them, but you can make them out.)
2. One of the tarsal claws -- no denticles
3. A ventral view of the nymph, showing the dark anterior edges and the posterolateral projections.
Back to the streams tomorrow where I'll be finding more stoneflies -- and maybe some M. pudicum flatheads (if that's what they are!).
Tuesday, November 22, 2011
Yes, another rainy, gray, November day in Charlottesville.
I've mentioned in recent entries that the one mayfly I continue to find in almost every stream that I visit is the flatheaded mayfly, genus Maccaffertium. The one in the photo above was found at the Rapidan River last week. I've also mentioned (entry posted 10/6) that Maccaffertium species ID is no easy thing. But, it's a good day for microscope work, and there are two nymphs that I've found recently, both in very good streams, that look to me like they might be the same species. So, I'd really like to nail down what species that is. I'll give it a try in this entry, but you must keep in mind my "amateur" status -- my conclusions might be totally wrong.
The two nymphs I want to look at in greater detail are the one in the photo above, and this one, found on Saturday, 11/5 in the upper Doyles River.
I was struck right away with one feature they share: tergites 7, 8, and 9 on both nymphs are orange; tergite 6 is dark brown. Now, the two nymphs might not be the same species. But at the moment I think there's a good chance they are, and I've narrowed it down to either M. mediopunctatum or M. meririvulanum, both of which are found primarily in mountain streams.
What anatomical features do these nymphs have in common, features that point to the two species I've mentioned? There are five things at which we have to look, beginning with the maxillary crowns (put the nymph on its back and remove the labium).
I count 6 spines on the top edge of the maxilla; there are no "hairs" that follow the spines. The same is true on the nymph from the Doyles River -- 6 spines (there are hairs on the maxilla, but not on top.) The lack of hair on the crown of the maxilla eliminates about half of the Maccaffertium species we might expect to see in this part of the country (North Carolina has 15) from contention.
Doyles River Mac:
Secondly, if you look at the claws on the legs of the nymphs, there are no "teeth," no "denticles" (they're "edentate").
Doyles River Mac:
True, there is a "spur" on the tarsal claw, but that is not the same -- I think I'm right in saying this -- as denticles/teeth.
Number three, we have to determine if there are "lateral projections" (spiny points) on the abdominal segments preceding segment 6. In our case there are; were they not present we'd be looking at some different species.
Doyles River Mac:
The other things that are sometimes relevant to Maccaffertium species ID are the ventral and dorsal patterns. With M. meririvulanum, it's the dorsal pattern that matters. On Tergite 5 in nymphs of this species there is a pale colored "V"; this can also be seen on tergite 7, or even 7-9. I could convince myself that we do have "V's" on both of our nymphs. And keep in mind that these nymphs are still immature: colors and patterns are not yet fully developed.
Doyles River Mac:
But M. mediopunctatum nymphs have dark ventral bands on segments 2-8 and an inverted "U" on segment 9. Those features seem to be very pronounced on our nymph from the Rapidan River; not so much on the Doyles River nymph. (Have another look at the photos above showing the "lateral projections.") That could mean that we are looking at two different species (with a lot of anatomical features in common); it could also mean, however, that the nymph from the Doyles River is not as mature as the Rapidan nymph. Again, the ventral colors and patterns are not as developed.
Well, my results are inconclusive. But I do think M. mediopunctatum and M. meririvulanum are two good choices for identifying these fall/winter nymphs. And at least we were able to see what the experts have to look at when they work on Mac ID.
Saturday, November 19, 2011
Just when I said that, yes, I am finding some mayflies, but this is pretty much "stonefly season," I probably found more mayflies today -- four different families -- than anything else! But let me begin with an insect that presents a bit of a challenge. The Perlodid stonefly in the picture above -- what is the genus?
I found two of these nymphs. Here is the other.
They were tiny -- as in VERY small -- and dichotomous keys point out right away that you need to use mature insects for proper identification. So, I'm not 100% sure of my conclusions on this one, but I think the genus might be Yugus. Let me remind you of what mature Yugus nymphs look like. I found this nymph in the same spot in the Rapidan River where I was searching today back in March of this year.
So, am I nuts?! Well, I have two pieces of evidence that I can use for support. But I repeat, I'm not totally sure of the ID that I'm suggesting.
1) Yugus nymphs have a "labrum with [a] yellow mesal band" (pretty clear in the picture above), and 2) on a Yugus nymph, there is a "marginal lacinial setae row [that extends] from near [the] apical tooth to near [the] base (Peckarsky, Freshwater Macroinvertebrates, p. 71). So, let's look at microscope shots of the heads, and before we do that, please note the yellow "M" on the head of the nymph in the picture above.
And here's a shot of the lacinia on the larger of the two nymphs, on which the setal row does indeed extend from the spine at the tip at least half way down to the base.
The evidence that I see -- keeping in mind how the colors and patterns change and develop on these nymphs as they grow -- argues in favor of Yugus. But, for me, this is a tough one.
Let's move on to easier things. I found another unusual insect today -- a type of crane fly larva that we see only rarely. Have a look.
And let's have a close look at that rear end.
Now let me show you what happened to that rear end when this bug was preserved.
It turned into a bulb! This is a crane fly larva (family: Tipulidae), genus Hexatoma. The bulb gives it away, so too do the "ventral lobes," specifically the long hair on those lobes. Very interesting find; it's so different than the Tipula that we normally see.
I guess for the rest of the insects I found, I should just stick to pictures. I found small winter stoneflies -- a lot of them as I had expected -- and large winter stoneflies, some of the biggest ones that I've seen. There were also a couple of Chloroperlids (green stoneflies), along with Giant stones and Common stones (genus Acroneuria). But giving the small winter stonefly a run for its money in terms of dominating the sample today was the brushlegged mayfly! They were all over the place, and they're starting to get big. Let's begin there.
1. Brushlegged mayfly (Isonychia bicolor)
2. Pronggilled mayflies (genus Paraleptophlebia). There were a lot of these in the leaf packs as well.
3. One of many small winter stoneflies
4. A Chloroperlid -- and the Chloroperlid next to a Perlodid
5. A few beautiful large winter stoneflies -- and note how the wing pads are starting spread out and away from the body.
6. One of the Giants I found today (there are a lot of them in this stream), here giving the Chloroperlid a ride.
7. And last but not least, a spiny crawler -- Ephemerella subvaria. Remember that I found a tiny E. subvaria nymph in this stream on 9/13.