Photos from the Rapidan River

I went up to the Rapidan River on Monday to see if I could find any insects.  The water was high and fast, but I found quite a few things in balls of vegetative matter close to shore.

At the top of the page, a pretty cased caddisfly that really drew my attention.  The case looked a little unique, and at first I thought it might be a species I'd not seen before.

I preserved it and went home to do some microscope work.  The first thing to check was the lateral hump which looked like this.

The orange sclerite behind the hump signaled genus Pycnopsyche.  Since I often find Pycnopsyche scabripennis up there in the spring and summer, that immediately came to mind.  But the case looked somehow different.  At issue, the sticks extending back from the top of the case.  This brought to mind P. guttifera, a species that often makes this kind of case.  From the descriptions of Pycnopsyche larvae in Beaty's manual ("The Trichoptera of North Carolina," pp. 84-85) it became clear that the choices were guttifera or scabripennis.  These species share one thing in common -- both have "2 major setae" on the "ventral margin of the femora" (Beaty, p. 85).  That I could see.

(Note that the large setae behind these two is actually on the dorsal side of the femur.)  But, the species differ in one significant way -- on the venter of the first abdominal segment, there are more than 15 setae on guttifera, while on scabripennis there are less.   Microscope photo.

I've pointed to three of the setae; in all I counted ten.  So, I guess it was P. scabripennis after all, just a young one with much room to grow. 

Since I was so intent on getting good pics of the caddis, I totally ignored the spiny crawler mayfly that was hitching a ride on its case.  Pretty sure it was Ephemerella invaria, but I should have preserved it just to be sure.  Very unusual colors.

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I got some pretty good photos of two other insects.

1. Small minnow mayfly, Baetis tricauditus, male and fully mature.

and 2.  A young "Yellow Sally" stonefly, Isoperla kirchneri group (probably I. montana).

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The Rapidan valley in Winter.

Another free-living caddisfly species -- Rhyacophila torva

This is an exciting find I made a few weeks ago while exploring one of my favorite streams in Sugar Hollow.  The stream is on the land of a good friend who often goes with me to look for stream insects. 

This is Rhyacophila torva, which brings the number of Rhyacophilidae species that we've found so far to seven.  It's the distinctive head pattern that convinced me that this was a new one for me, and it's the head pattern that's one of the keys to the species ID.

On R. torva, Beaty says the following: "R. torva -- larva ?? mm; teeth on anal claw present; distinct dark "V" along frontoclypeal sutures with some darker muscle scars behind.  Occurs mostly in small Mountain streams.  Relatively common.  Recorded from GSMNP. (Steven Beaty, "The Trichoptera of North Carolina," p. 61.)

With that, all I had to do was get a microscope shot of the anal claws, and the teeth on the claws was obvious.  (In another source -- unpublished -- there's an illustration of an R. torva claw.  It too shows a claw with 3 teeth that are progressively smaller as you move the tip to the rear.)

I should add that, yes indeed, it was found in a small mountain stream!

Love finding new things!
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As you can see from the photo above, it was a gorgeous day, one of the few really nice days we've had so far this winter.  Consequently, we found a few other things that made for good photos.

1. Small minnow mayfly, Baetis tricaudatus. 

2. A second Rhyacophilidae species -- R. carolina. 

and 3. A Roach-like stonefly, Tallaperla sp.

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I'll be posting again tomorrow -- photos from a trip to the Rapidan river I took yesterday.  Got some good ones.

One other thing. For the last year I've been actively posting on Instagram.  You can find me at: buddhabob2hanlubo.

Big News: Isoperla sp. VA has been identified as Isoperla nelsoni

I have several entries to post, but I'll start with some big news from Steve Beaty.  The Isoperla stonefly nymph that we've been finding in a number of small streams in Sugar Hollow which had the temporary designation of Isoperla sp. VA has now been identifed as Isoperla nelsoni.  Exciting news to those of us who see it every spring -- usually in April and May -- but have failed to find any adults to help us with the ID.

Isoperla nelsoni, the adult, was first described in a long article by S.W. Szcytko and B.C. Kondratieff, pp. 174-177 in "A Review of the Eastern Nearctic Isoperlinae (Plecoptera: Perlodidae) With The Description of Twenty-two new species," Monographs of Illesia, Number 1:1-289 (2015). 

One thing of interest, the head pattern we see on the mature nymph, this,

with a dark patch enclosed in the ocellar triangle and a dark patch anterior to it, shows up as well on the head of the adult.  (See the illustration of that on p. 175 of the article.)

Exciting news.  We had found this nymph first in May of 2011.

New Insects from Oregon: Drunella spinifera and Rickera sorpta

It's been awhile since I've posted an entry, but it's been awhile since I found anything new.  But I lucked out last week when we went to visit our daughter in Oregon.  On a trip up to Mt. Hood, we stopped at a small stream in which I found some new -- for me -- insects.

Let's start with the easy one, the spiny crawler mayfly, Drunella spinifera.  (In the photo above and the photo below)

As I always do when I try to ID bugs from the Northwest, I turned to the website managed by Roger Rohrbeck, PNW Mayflies (Fly Fishing Entomology).  Rohrbeck describes seven different species of Drunella nymphs, and the one that works for us is Drunella spinifera.   His description reads: "Femora of front legs very broad, but don't have bumps on front edge; long sharp tubercles on back of head; abdominal tubercles 8-9 more than twice as long as 2-7."  Here's a look at the fore femora:

Other species of Drunella do have bumps on the front edge.  E.g., in case you've forgotten, here's a look at the fore femora of Drunella cornutella, a species we find in our streams in VA.

Dramatically different.  The shot I took of the tubercles on the head --

don't show the "sharpness" very well (bad angle on my part), but check out the tubercles on the abdominal segments.

The tubercles on segments 8 and 9 differ markedly from those on 2-7.  No doubt about it, our nymph is Drunella spinifera.  I might add that on his website "troutnut.com," Jason Neuswanger notes that this is a species that "prefers cold water," and inhabits "high elevation headwaters."  We were at about 3000' ASL.
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Now on to the toughy.

As you can see,  it was a very small stonefly nymph which makes the ID all the more difficult.  However, I have reason to believe that it was Rickera sorpta.  This genus and species is described on p. 440 of Stewart & Stark, Nymphs of North American Stonefly Genera.  There, the head is described in the following way: "Head with dark, broad, irregular U-shaped mark connecting ocelli; light oval interocellar spot. Light area anterior to median ocellus."

On target so far.  On the lacinia -- "Lacinia triangular and unidentate, with 5-6 basal marginal spinules and 2-3 medially located marginal spinules."

Unidentate for sure.  I didn't note any spinules, but this was a very small, very young nymph.  Now for a critical feature.  "Y-arms of mesosternum meet posterior corners of furcal pits, and transverse suture connects anterior corners of furcal pits."  The connecting suture is illustrated on p. 442 (Fig. 14.50), and it appears to be in the shape of a slight arc.  Here's the best photo that I could manage.

I've put a rectangular box around this suture to help us focus.  I'd say they're connected for sure.  One other feature.  Rohrbeck adds that there are "dark and light stripes on the abdomen" (PNW Stoneflies). 

And there they are. 

I only hesitate on my ID because there is another taxon -- Kogotus nonus -- that looks a lot light our little nymph.  The head pattern's much the same, and there are dark and light stripes on the abdomen, and the lacinia is unidentate.  This is one that I found a few years ago in Montana.

How do they differ?  It has to do with the presence or absence of that suture connecting the furcal pits of the mesosternal Y-ridge.  It's present on Rickera, absent on Kogotus.  I'll stick with my ID of Rickera sorpta, for the moment at least, since I do see that suture on our small nymph.

So much fun to find something new and to work on the species ID.  I should note, by the way, that I'm now posting photos on Instagram.  Look for me under "buddhabob2hanlubo". 

Cinygmula subaequalis: do the nymphs differ by gender?

One of the flatheaded mayfly nymphs that easy to ID, even just using a loupe in the field, is Cinygmula subaequalis (subaequalis is the only species in the Southeast).   We need only note the two bumps at the sides of the head, which are the maxillary palpi.

But the color patterns I've seen on the nymphs that I've found aren't always the same.  Some, like the one in the photo at the top of the page, are essentially brown, others like this one

have a distinct pale area on the frons (the forehead). 

Last Sunday, I found two nymphs at the Rapidan River, one of each type.

It occurred to me that this might be a gender distinction, something we commonly see with small minnow mayflies, so I ran this by Steve Beaty.  He wasn't convinced, feeling that those with the pale areas on the top of the head might simply be nymphs that have just recently molted.  But I still wonder about this for one very good reason: the distinction is one that's consistent.  That is to say, where there are pale areas on one of the nymphs in the photos above, there are pale areas on the other nymph as well.  Have a look.

There's the spot on the head -- which is shaped the same on both of our nymphs, a second spot on the mesonotum, and the first tergite is pale.  (So too are terga 9 and 10, but that is also true of our solid colored nymphs.)  This is something I wouldn't expect if this were simply a matter of molting.

Time will tell, but I'll keep an eye out for these features on other nymphs that I find.
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Some other nice pics at the Rapidan River last week.

1) A fairly mature Ephemerella subvaria.

2) The stonefly, Agnetina capitata.

And 3), a rather spectacular pronggilled mayfly, Neoleptophlebia assimilis.

If you're a fly fisherman, pretty clear that the Blue Quills are hatching.

An odd pair of spiny crawlers at the Doyles River yesterday

It's the time of year when we see a lot of spiny crawlers in all of our streams, for the most part, genus Ephemerella.  E. invaria nymphs are present in appreciable numbers from February to April; E. dorothea nymphs show up in HUGE numbers from April to May to June.  I saw a lot of them yesterday at the Doyles River including this striking pair, male and female.

It wasn't until I got home and downloaded my photos that I noticed just how striking they were.  What's unusual is the orange spots on the sides of terga 5 and 6 and at the top edge of the mesonota.

Thinking I might have found a species I'd not seen before, I did the microscope work, using Beaty's "The Ephemeroptera of North Carolina" as my guide.  In the end, they keyed out to E. invaria, or rather, "E. invaria group".  Let me review the critical features.

Nymphs 6-13 mm; pale transverse stripe between eyes, may be interrupted medially; tarsal claws with 5-10 denticles; abdominal terga with short, sharp, paired submedian tubercles on segments 2-9, rarely on 2, sometimes barely discernible on segments 3 and 8, small on 4-7, rarely on 9; posterolateral projections on abdominal segments 3 or 4-9 (variable to absent on 3); may have dot-dash pattern on pale ventral surface and speckling on last few segments.  ("The Ephemeroptera of North Carolina," p. 52)

1) Our male nymph measured 6 mm, the female -- the larger and lighter of the two -- measured 8.

2) The pale stripe between the eyes is clearly visible on both of our nymphs; they don't seem to be "medially interrupted."

3) I could see 5 denticles on the tarsal claws, with a dark spot behind them (more denticles?).

4) On the female nymph (didn't check the male), there are paired, sharp pointed tubercles on segments 3-9.  In this photo, I've pointed out those on segments 4 and 5.  (Note, the "tubercle" is just that part of the pale spot that projects beyond the rear edge of the terga.)

5) There are posterolateral projections on terga 4-9, and yes, the last few ventral segments are speckled, and the dot-dash ventral pattern shows up very clearly.

So, Ephemerella invaria nymphs for sure.  But two things to keep in mind.  Beaty notes that "This is the most variable Ephemerella species in terms of size, color pattern, and size of tubercles," number one, and two, E. invaria is now considered to be a "group," which includes the species E. inconstans and E. rotunda.  No way to know which member of the "group" I found without finding some adults.
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The other taxa that is crowding our streams at the moment is Isoperla montana, the nymphs that hatch as "Yellow Sallies" for you fly fishermen.  They were also prominent yesterday.