Always a nice surprise: the "green stonefly" (Chloroperlidae), genus Alloperla

So small -- but so pretty.  Chloroperlid -- green stonefly -- Alloperla sp. I don't see this one often, but I have found them before in Buck Mt. Creek, my destination this morning.  However, in reading Beaty's description of Alloperla ("The Plecoptera of North Carolina," p. 27, Vers. 4) I discovered why they seem scarce.  "Alloperla and some other chloroperlids are likely under-collected due to the nymphs presence in the hyporheos."  (The hyporheos is "a region beneath and alongside a stream bed where there is mixing of groundwater and surface water." -- Wikipedia.)  Glad I've started to spend more time digging around in the substrate.

These stoneflies are small -- this one measured 6.5 mm -- but the green color helps us to spot them.  For the ID, "Nymphs 5.7-9.6 mm.  Head with posterolateral margins rounded with eyes large and set midlaterally;

pronotum with setae usually restricted to corners;

mesal portion of posterior margin of abdominal sternum eight lacking setae; middle and distal segments of cerci with a dorsal and ventral fringe of long setae, each segment with 2-6 long intercalary setae."  Don't have a real good photo of this, but this does show the numerous long setae on the distal segments.

Beaty doesn't note the feature that I thought was important: the inner edges of the wingpads angle away from the central axis of the nymph.

Species name?  Beaty advises us to stay at the level of genus noting: "North Carolina has a least seven species of Alloperla of which three are undescribed in the immature aquatic stage."  Well, that means that four species have been described, so I'll have to do some research to see what I can find.  In the meantime, the known species are atlantica, chloris, lenati, nanina, neglecta, petasta and usa.

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Actually, my goal today was to find more Perlesta -- and I did.

Hope to say something soon on distinctions I'm noting on the Perlestas from various streams

Perlesta from a small mountain stream -- check!

I don't hold out much hope that we'll be identifying Perlesta stoneflies to the level of species anytime soon.  But it's possible.  After listing 13 possible species in North Carolina, Beaty goes on to note "North Carolina has very high diversity of Perlesta, most of which are undescribed at this time.  At least five species from NC are currently being associated." Maybe we'll get lucky.

But since it's June -- Perlesta season -- I thought I might collect some of these nymphs from different streams/locations to see if there are differences that we can discern.  Different species of stoneflies tend to differ in observable features on the heads, pronota, and the abdominal terga.   First stop today, one of our small headwater streams in Sugar Hollow, which was loaded with them.  Some pix.

On the nymph at the very top of the page, we can see the features we need for ID: 1) there is a complete setal row on the occiput (back edge of the head) with irregular gaps (see Beaty, "The Plecoptera of North Carolina," p. 19.)

better yet, a microscope view

and 2) the abdomen has a speckled appearance from the dark intercalary setae on the terga.

It is worth noting, however, that those setae on this nymph are much less pronounced than they were on the nymph I found in Buck Mt. Creek on 5/28.  This one.

Different species?  Too early to tell, but I'll be looking closely at features like these.  (Also note that the terga on the nymphs found today have narrow, dark transverse bands on the anterior and posterior edges.)
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Only took photos of one other Perlid today -- a fairly mature Eccoptura xanthenses.  Beautiful colors.

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Rapidan in the morning.
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Interesting note.  When Unzicker and McCaskill published their study of Plecoptera (pp. 5.1 - 5.50 in Aquatic Insects and Oligochaetes of North and South Carolina, 1982), they wrote the following on Perlesta: "Two species of Perlesta are known from North and South Carolina, P. frisoni Banks and P. placida (Hagen).  The nymph of P. placida has a conspicuously speckled abdomen.  The nymph of P. frisoni is unknown.  Frison (1935) recorded Perlesta nymphs from the Great Smoky Mountains National Park in Tennessee which had lightly speckled abdomens.  These nymphs should be labeled as Perlesta sp. until the status of P. frisoni has been determined." (p. 5.28) Perlesta study has come a long way.

Mature insects galore in Sugar Hollow

It's that time of year when this season's "crop" of mayflies and stoneflies is about to take wing.  And I found a lot of nymphs that will probably hatch later today.  Black wingpads.

This one -- the flatheaded mayfly Epeorus pleuralis.  Many, if not most, of them have hatched in April and May, but there are still some hangers-on.   11 mm.

And this is the spiny crawler, Ephemerella dorothea.  Our streams have been clogged with them throughout the spring.  Personally, I'm glad to see them go (sorry!).  Of the many that I saw this morning, this is the only one that was fully mature.

Lots and lots of the small minnow mayfly, Baetis tricaudatus, and four of those in my tray were also decked out in black wingpads.  Unfortunately, on this gray cloudy morning, the photos I took weren't really worth posting.

And then there was this fully mature "common" stonefly, Acroneuria abnormis.  I think this is the first time I've seen one of these nymphs with black wingpads.  That's pretty amazing.  I suspect that this was a male: it was only 17 mm.  This A. abnormis nymph, on the other hand, was 25 mm and as you can see, it's not quite ready to go.

Remember that the Perlids ("common" stoneflies) hatch in June and July as Golden Stones, at least the group that's maturing this year.
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Good weather next week, or so they're saying right now.  So I'll be out in pursuit of yet another nymph that should be mature -- Isoperla sp. VA.

The spiny crawler Drunella cornutella: lots of them today at the Doyles

I noted in my last entry that I should stick to the small mountain streams for awhile: should have done that today.  The Doyles River at Blufton Road was high -- and actually a little off color.  Consequently, a lot of the insects I found were covered with silt, though it is true, Drunella nymphs are often that way when I find them.  Must be where they live.

The spiny crawler in the photo above is Drunella cornutella.  It's one of three species we have in our streams -- the other two, D. walkeri and D. tuberculata -- but it's the one we most commonly see in late May and June.  I netted four of them today in the short time that I worked in the stream, two of them already mature -- black wingpads.

Drunellas are easy to spot, those muscular fore femora give them away.  For D. cornutella, let me turn to Steve Beaty's "The Ephemeroptera of North Carolina."  "D. cornutella -- nymphs 6.4-8.5 mm; head smooth with moderately long lateral frontoclypeal projections but less than half as long as the distance between them; median ocellar tubercle blunt to moderately sharp; femora with dense row of long, fine setae on posterior margin; ratio of mesotibia to mesofemur <0.85; abdomen without paired dorsal tubercles. Collected in spring through early summer.  Common."

The nymphs that I found were 7-7.5 mm.  We can see the critical features for the cornutella ID in a single microscope picture.  Also clear in that photo,  the tubercles on the front edge of the forefemora that signal the genus ID.

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Back to the small streams tomorrow.

Oh.  Also a lot of Perlesta stoneflies around.

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.

and

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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.

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.
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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.

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 et.al. 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.
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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.

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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.

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So satisfying to find some good insects and get decent photos.  Up to the Rapidan River tomorrow.
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Oh, by the way.  Steve Beaty joined us at this stream last month.  That's him on the right.