A fresh look at the problem of Rhithrogena species ID

I found this little nymph at Buck Mt. Creek last Thursday (4/11/19),  and since we have a new key to use for species ID -- Morse, McCafferty, Stark, and Jacobus, Editors, Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species, 2017 -- I thought I might see if I could work out the species ID.  My conclusions should be seen as tentative since I know from Beaty that work still needs to be done on this genus, and the descriptions in our new book are indeed rather tentative.  Nonetheless, using this key, I'd conclude that, to date, I've found three different species.

1. Rhithrogena uhari (the nymph above)

The description of R. uhari reads as follows: "Abdominal terga light yellow brown to light chestnut brown to cinnamon brown; conspicuous dorsal abdominal marking not present in darker forms but some diffuse pairs of markings sometimes evident in lighter-colored forms, including pairs of cloudy patches laterally." (p. 122)

The color sure seems right, and I do see pale paired dots on the terga as well as interesting lateral markings on all of the terga.  Can't say if they're "cloudy," since I'm not sure what that the editors have in mind.

So, possibly R. uhari.

2. Rhithrogena exilis

Beaty told me sometime ago that this one would key out to exilis, even though he cautioned to take that ID with a grain of salt.  Here's the description of exilis in our new key.  "Abdominal terga 1 and 2 pale yellow; terga 3-6 dark reddish brown and unmarked except for yellow or yellow-hyaline lateral margins; terga 7-9 yellowish, unmarked."  (p. 122) This one works out pretty well: terga 1 and 2 are indeed pale, as are 8 and 9 -- can't say that's true for tergite 7.  But, I do see pale markings on the terga.

3. Rhithrogena fasciata

This nymph is clearly darker than the two we've looked at above.  Here's the description of R. fasciata.  "Abdominal terga medium to dark brown or orange brown; terga 1 and 2 sometimes pale; terga 4-8 sometimes darker anteriorly and paler posteriorly; terga 7-9 often shade lighter than preceding terga." (p. 122)

Certainly true that terga 1 and 2 are pale, and terga 8 and 9 are clearly a "shade lighter than the preceding terga" -- not sure I could say that of segment 7.  It is not the case that terga 4-8 are "darker anteriorly and paler posteriorly," rather, it seems that the posterior edge is darker.  That character doesn't apply to any of the species that our key describes, so maybe it's a variant with this species.  But that exception should be noted.
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Results and conclusions are tentative for sure.  Still, I'd argue that we've clearly found three different species, and they key out pretty closely to uhari, exilis, and fasciata.  Be in touch if anything new shows up on this one.

Another new insect: an Ameletidae, Ameletus tertius

I found this little mayfly at the Rapidan River on Tuesday, and when I looked at it in the bowl, my first guess was that it was nothing but the small minnow mayfly, Baetis intercalaris.  Still, something wasn't quite right.  It was only when I focussed in to get some photos that I realized this was something I'd not seen before.  By the shape of the head, the short antennae, and the fact that the gills pointed straight up and down -- sort of like the oar blades on a crew boat -- I knew that it was Ameletidae,  but what species?

When I got home I looked at Steve Beaty's descriptions ("The Ephemeroptera of North Carolina," p. 1) in which five different species are keyed out for this part of the country -- cryptostimulus, lineatus, ludens, tarteri, and tertius.    The A. tertius description caught my eye for one prominent reason: "distinctly marked small species with dorsal terga 3-6 with two large, ovalized submedian segments" (Beaty, p. 1)  Bingo!

And another feature shows up in this photo as well -- "tarsi with both dark basal and apical bands." (Beaty)

But there were two other features that required some microscope work: 1) "ventrally pale except sterna 9 and 10 darkened (also sometimes a portion of 8)," and 2) "posterior spinules on abdominal terga 1 or 2-10."

Yes in both cases (though I realize it may be difficult in my photo to see the spinules except for those on segments 5 and 6, they were present on all of 2-10.)

Score again for the Rapidan River -- Ameletus tertius!  Here's some more photos.

Sometimes I wonder why I go to other streams.


A. tertius is the fourth Ameletidae species I've found.  The others,

Ameletus cryptostimulus,

Ameletus lineatus,

and in Montana, Ameletus subnotatus.

Ironoquia punctatissima: a new caddisfly casemaker in a small stream in Sugar Hollow

Yesterday afternoon, I went with a friend to a tiny stream in Sugar Hollow, one in low-lying ground.  It was shallow and slow-moving, just a couple of feet wide, but there were some small riffles here and there and the occasional leaf pack.  To our surprise, we saw a fair number of insects including this casemaker which turned out to be Ironoquia punctatissima (Limnnephilidae).

Two things were clear from the very beginning in terms of key features: for one the case was rounded and slightly curved, seemingly made out of rows of pieces of bark, and secondly, the gill tufts were multi-branched.  Take a close look.

Leafing through Wiggins -- Glenn B. Wiggins, Larvae of the North American Caddisfly Genera (Trichoptera) -- I found what looked to be a pretty good match in the Limnephilidae genus, Ironoquia, so that's where I began. (pp. 249-249 in the 1977 edition)  On the genus morphology, Wiggins wrote the following things: "Ironoquia, one of four North American limnephilid genera in which most abdominal gills of the dorsal and ventral rows have more than four branches, is distinct from the others in having more than two (usually five) major setae along the ventral edge of the middle and hind femora.  Many metanotal setae arise from the integument between the primary sclerites.  Length of larva up to 22 mm."  All of this worked out to be perfectly true.  Here are the key microscope photos.  (And this larva was about 18 mm.)

For additional confirmation, we can look at what he says about the type of case and the habitat in which this genus is found.

"CASE  Two types of larval case are known.  In I. punctatissima and I. lyrata cases are made of bark and leaves, curved but little tapered; the case of I. parvula is made of sand grains." (p. 248)

"BIOLOGY Although North American larvae of the subfamily Dicosmoecinae are largely restricted to cool, running waters, species of Ironoquia are the sole exception, living in temporary pools and streams." (p. 248)

Beaty says much the same on the habitat of this genus: "Found in temporary streams as well as swamp streams." ("The Trichoptera of North Carolina," p. 82)  I have no problem thinking that this was a temporary stream, one that dries up in dry summers.

What about the species?  For this I had to turn to the new book by Morse, McCafferty, Stark, and Jacobus -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species (Clemson University, 2017).  They note, and illustrate, two possibilities: punctatissima and parvula. (pp. 392-393)  The difference between the two has to do with the head and nota.  For Ironoquia punctatissima -- "Head and nota pale with dark spots and infuscations" (p. 392): and for Ironoquia parvula -- "Head and thoracic nota dark with pale central stripe" (both types of head are illustrated on p. 393)  No doubt about it, we've got a head that is pale with dark spots.

Ironoquia punctatissima -- so much fun to finding something new.
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We also found a mayfly that might be a new species for me -- Eurylophella funeralis.

But these little nymphs are hard to get down to the level of species.  To do that, we need a clear look at the abdominal tubercles, and the two nymphs we found yesterday were dirtied up with detritus.  (Sigh.  I wish someone made a tiny, tiny brush that we could use to clean these guys up!)  (:

In any event, we really enjoyed taking a look at this stream, and you can be sure we'll work on it more in the near future.

Photos from the South River and Entry Run

The weather was perfect yesterday so I headed up to Greene County to look for bugs in Entry Run and South River.  I wasn't disappointed.  On some of the rocks I turned over, there were 20-30 nymphs, both Epeorus pleuralis (Quill Gordons to fly fisherman) and Baetis tricaudatus small minnow mayflies.  It was really awesome.  It wasn't hard to get some pretty good photos.

1. Baetis tricaudatus, female, several shots including the one at the top of the page, and one with one nymph on its side and another on its back.

2. A flatheaded mayfly, Epeorus pleuralis.

3. A "common netspinner," Hydropsyche (C.) alhedra.  Remember that this netspinner species is very intolerant, rating 0.0 on a scale of 0-10.

and 4. A "free living" caddisfly larva, Rhyacophila fuscula, with a good look from the side and underneath.

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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.