Saturday, May 28, 2016

Common stoneflies -- uncommonly colorful: Perlesta at Buck Mt. Creek

Just back from Buck Mt. Creek where the water remains high and slightly off-color.  Just need to stick to the small mountain streams for a couple more weeks.  But, no problem finding insects: my tray was loaded with tiny, small minnow mayflies.

And, no surprise I found some Perlestas (common stonefly, Perlidae).  They really are "common" in our streams at this time of year, and as a genus Perlesta is fairly tolerant for a stone -- TV of 2.9.  Clearly, when more work is done, we'll find that the TV will vary with species.  As I noted a few days ago, we find them in our very small headwater streams, in medium waters like Buck Mt. Creek and the Doyles, and in our "large" river, the Rivanna.

I took photos of two nymphs this morning, the two quite different in color.



When I look back at Perlesta photos I've taken in previous years, one of the striking things is the different colors of the nymphs that I've have seen.  Have a look.

What I don't know, of course, is whether these variations are a matter of species, habitat, or maturation (which clearly plays some sort of role).

For genus ID, I turn to Steve Beaty's "The Plecoptera of North Carolina," p. 19: "Nymphs 8-12 mm; setal row on occiput complete, sinuate, and with irregular gaps; abdomen with numerous short, stout intercalary setae, often with pigmented bases giving abdomen a speckled appearance; anal gills present; body covered with fine, dark clothing hairs."

No need for microscope photos to discern these critical features.  For the occipital setal row, the intercalary setae (speckled appearance), and the anal gills

and for the dark clothing hairs.

Most common month to find Perlestas out there -- June.

Wednesday, May 25, 2016

And it's a new Rhithrogena at the Rapidan River. Species? Could be R. manifesta

Maybe the most colorful mayfly nymph that I've ever seen.  Yellows, browns, oranges -- just spectacular.  I knew when I was taking these photos that this was something new, and I suspected a flatheaded mayfly, but I wasn't sure of the species until I had it under my scope.  Rhithrogena.  "Abdominal gills 1-7 enlarged and meet ventrally forming a ventral disk; three caudal filaments; color variable on mid-sized specimens." (Beaty, "The Ephemeroptera of North Carolina," p. 22)

Unfortunately this is one of the genera where Beaty urges caution, noting "A fair amount of color variation and overlap of characters make Rhithrogena species determination difficult.  Leave small, immature specimens at genus."  Were I to wager a guess, I'd go with R. manifesta: "nymphs 7 mm; abdomen dark brown with tergites 8-9 bright yellow; sternites 2-8 with dark median rectangular patch containing a narrow, dark, transverse line near posterior margin. ... Recorded from SC, TN, and VA."  This nymph was 6-7 mm, and I could be persuaded that those are "dark median rectangular patches" on sterna 2-8.  But we'd better not jump on that ID since this nymph is still immature.  (Be in touch if I hear something from Beaty.)

Gorgeous.  Without any question, one of the most colorful insects I've found.

The Rapidan is still high and fast after the 2-3 inches of rain we had over the weekend.  Still, I found lots of insects.  One other beauty, a fairly mature common stonefly Agnetina capitata.  I'd guess that this one will be hatching come July.

But what a treat finding that Rhithrogena.

Tuesday, May 24, 2016

Some awesome photos today: back to Sugar Hollow

Tough to know where to begin today: we found some beautiful insects.

Above, our as yet unidentified species of Isoperla ("stripetail") .  Consequently,  Beaty have it labelled Isoperla sp. VA.  As I noted last time, we're on the lookout for some nymphs that are fully mature, nymphs we can rear to point that they hatch.  This one's not quite there, but the "tan" wingpads are one instar before they turn black.  So I kept him just in case I get lucky.

The stream that we went to today -- the little gem where my friend lives -- was loaded with them.  I took two nets and had 10-12 in my tray.  Have to look next week for some that are fully mature.

And then we have the Leucrocutas.  What a gorgeous insect.  Pretty sure this is L. juno, but as you'll remember, entomologists want to hold off on species ID until more work has been done.  In any event, they too were abundant today.  I took photos of this mature nymph and one that's still sort of young.


Finally, a young Stenacron nymph.  You might recall that the distinguishing feature of Stenacron nymphs is the shape of the gills: they come to a point.

Beaty: "Abdominal gills 1-6 with apex pointed, seventh gill filamentous; three caudal filaments." ("The Ephemeroptera of North Carolina," p. 22)

This nymph is Stenacron carolina, and the key thing to examine is the pale spot on the head.  "S. carolina -- nymphs 10-13 mm; length of pale triangular spot anterior to median ocellus approximately 2X it's basal width (provisional) ...dorsum of abdomen grey-brown without conspicuous markings; caudal filaments all light grey brown with no banding.  Usually in small mountain streams.  Collected spring to summer.  Uncommon." (p. 22)

You can see that "pale triangular spot" very well on almost all of my photos.

And here's a microscope view.


So satisfying to find some good insects and get decent photos.  Up to the Rapidan River tomorrow.

Oh, by the way.  Steve Beaty joined us at this stream last month.  That's him on the right.

Friday, May 20, 2016

It's the annual "spiny crawler" invasion: Ephemerella dorothea

Actually, they're kind of a nuisance at this time of year.  For the last 3-4 weeks, when I sort through my tray to see what I've collected, it's hard to get past these spiny crawlers.  It has to be one of the biggest hatches all year, and they come out as -- in fly fishing terms -- PED's, Pale Evening Duns.  Early on in the year we tend to see Ephemerella invaria, but Ephemerella dorothea dominates the invasion each spring.  The main clue for the ID -- no turbercles on the posterior edges of the abdominal terga.

In a previous life when I monitored streams, I had the impression that when spiny crawlers dominated our net counts, we had hit upon a poor quality stream.  Just not true.  It's just what we run into at this time of year.  This morning I was at one of our headwater streams in Sugar Hollow.  My tray was loaded with them.  I normally ignore them when I'm taking photos, but I thought the colors on this one were nice.

My search for Isoperlas continues, but I think I'm too late for anything but I. holochlora.  Still, I found this mature Isoperla sp. VA on May 18 in 2011, so there's hope.

I know Steve Beaty would LOVE me to rear one of these till it hatches.  We need an adult to detemine species ID, and, this could be a brand new species.

Two nice pics from this morning.  The first, a flatheaded mayfly, Maccaffertium pudicum.

And the second, a pair of small Perlestas.  Guess they do inhabit these cold, mountain streams.

Monday, May 16, 2016

Just back from Entry Run: no surprises but some good photos

So disappointed.  I was up pretty high on Entry Run -- 1600 ft. -- but nothing different than the insects I find down lower.  Only Isoperla I found: Isoperla holochlora.  Need to get up even higher.
But, at least the sun is back out!

Baetis tricaudatus, the small minnow mayfly we find in these high quality, small mountain streams.  As you can see, this one was ready to hatch.  Put it back in the water.


And the common netspinner we find in these streams: Diplectrona modesta.  This one's much more intolerant (TV 2.3) than the Hydropsychids we find in larger streams.  I keep thinking I'll run into Diplectrona metaqui, though it is listed as "rare".  (Beaty, "The Trichoptera of North Carolina," p. 74)
D. metaqui has an asymmetrical notch on the anterior margin of the head: on D. modesta, the margin is "entire" (= straight across).  Like this.


Found two Haploperla nymphs.  One was quite immature.


And there were a lot of Acroneuria abnormis common stones.  This was the biggest.

But it sure was a beautiful stream.  Boulder-strewn.

Sunday, May 15, 2016

Perlesta stoneflies -- still have to leave them at the level of genus

A little surprised by this one this morning -- not that we shouldn't be finding Perlestas (common stonefly, Perlidae) at this time of year -- this is when we normally see them (May, June, July), but I was in a small mountain stream.  Don't see many Perlids in this type of stream other than Eccoptura xanthenses.  That means that there are Perlestas in most (all?) of the streams that I visit, from these small, first order streams, to medium streams like the Doyles and Buck Mt. Creek, to our large river, the Rivanna.

While most Perlids are multivoltine (life cycle of 2-3 years), Perlesta is not.  It matures, hatches, and mates within the space of a year (univoltine).  And, unfortunately, we're still in the dark on the question of species ID.  As I've mentioned before, Steve Beaty published online a revised version (4.1) of "The Plecoptera of North Carolina" just last year in December.  But his advise on Perlesta remains the same: "LEAVE AT GENUS".  (p.48)  He lists the names of 13 different species but notes that "most of [these] are currently undescribed in the immature stage." (p. 49)  So we wait.  I have no doubt that the species that I found today is not the same as those that I find in the Rivanna.

I had high hopes of finding some new Isoperlas today, but all that I saw was I. holochlora.  Maybe tomorrow at Entry Run up in Greene County.


Just two other pics from today.  A fairly mature Ameletid: Ameletus cryptostimulus.  (There were a lot of them.)

And a small Leucrocuta flatheaded mayfly, the one that I think is Leucrocuta juno (see the entry of 5/27/15).   Regret that the tails aren't fully intact.

This too, is a species I only see in first order streams.