Exploring new waters: Rose River, Madison County

I'd like to explore some new streams in the winter and spring, so yesterday I went up to the Rose River in Madison County.  It's good water, known for some of the best trout fishing in central Virginia.  While I found a lot of good insects, I was surprised by the number of midges I found but pleased with the photos I got of them.

If you monitor streams, you come to expect these little larvae in your nets.  You might -- mistakenly, as it turns out -- assume that all midges are "tolerant" critters that indicate so-so water.  That's not true at all.   In North Carolina's list of tolerance values, there must be 500-1000 species of Chironomids listed, and they run the full range of TV's from 0.0 to 10.  So as it turns out there are "good" midges out there, and I suspect that's true of the ones I found yesterday given the quality of the water involved.  This is where I was looking.

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I didn't find anything new yesterday, but I did find of couple of nymphs that, before this, I had only found at the Rapidan River: the common stonefly, Agnetina capitata,

and the spiny crawler mayfly, Ephemerella subvaria.

I plan to back to the Rose in the winter and spring.  I expect to see some pretty good insects -- maybe even something new!
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A couple good photos of a brushlegged mayfly.  Still no way to key out the species.

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(I might add, by the way, for our readers who are fly fishermen, that almost all of the midges we see are this color.  Helps to know that for midge imitations.)

The "Strong Casemaker," Psilotreta rufa: It's a new species for me

It's not all that often that I find what I'm after, but I lucked out this morning.  This is a caddisfly that my friend found a number of years ago in the pristine stream that flows by her home, but this is the first time I've seen it.  Odontoceridae (Strong Casemaker), Psilotreta rufa.

Location?  Same stream as before.

But it didn't look like that today.  Today, the flow was reduced to a trickle.  The drought we've had here this fall has really taken a toll on these small streams in Sugar Hollow.  We were lucky to find anything in there at all.

Let's establish the species ID using Beaty ("The Trichoptera of North Carolina," p. 97)

(P. rufa) -- larvae up to 11 mm; head and pronotum uniformly reddish brown without stripes but may have darker pigmentation along frontoclypeal and coronal sutures...head longer than wide and relatively flat between carinae; seta 17 about half the length of seta 15; pronotum darker laterally; anterolateral pronotal projections short.

1) Our larva was 10 mm.

2) Yes, on the color of the head and pronotum -- "uniformly reddish brown" -- and yes, dark stripes are missing.

3) It's hard to see the frontoclypeal and coronal sutures in any of the photos I've taken.  Still, you can easily see that the entire top of the head -- the frontoclypeus -- is darker than the sides.

4) Yes, the head is longer than wide, and it's relatively flat between the carinae.  For the carinae, let me use a photo my friend took some time ago.

5) The lengths of setae 17 and 15 are critical to the ID, and I was able to get a decent microscope photo showing them both.

For sure, seta 17 is about half the length of seta 15. 

6)  I can't say that the pronotum on this larva looks darker laterally than the rest (except for tips of the projections), but the pronotal projections are definitely short.

Psilotreta rufa.

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This is the third species of Psilotreta that I've found in our streams.  On the other two, by the way, there are black stripes on the head and the pronotum.

Psilotra labida

and Psilotreta frontalis

Looking like winter at Buck Mt. Creek

I decided to see if the small winter stoneflies have shown up at Buck Mt. Creek and no problem, there were lots of them in the leaf packs.  Above a female; below a male.

The males are smaller than the females, have smaller wingpads, and have an extension at the end of the abdomen called a "supra anal lobe".

I was a little surprised to see that the male was almost mature -- note the dark wingpads -- but it's not all that unusual.  Once they show up, they mature and hatch in a short period of time.

Two other things.  First a small common stonefly, Agnetina annulipes.

These nymphs are common in the Rivanna in the fall: Buck Mt. Creek is the only other stream in which I've found them.

And there was one, young, Helopicus subvarians Perlodid stonefly, still quite immature.

We find mature nymphs in April.

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Sunny days in the forecast.  Maybe a trip to the Rose River?

Checking the Rapidan River

Yesterday I went up to the Rapidan River to check on the flow and habitat conditions.  The good news is that the water levels are normal again: the bad news is that the leaf packs have not decomposed to the point where there are large numbers of nymphs in them chomping away.  Still, I got some pretty nice photos.

1) Above and below, the uncommon, "common stonefly" (Perlidae) Agnetina capitata.  As you can see from the posterior edge of the wingpads this one was far from mature.   For that we have to wait until June and July.

2) The "brushlegged mayfly" (Isonychia sp.).   These were quite common.

You might recall that I was hopeful that, using our new key, I could get these down to species ID.  But alas, every nymph that I've found so far has a "cluster of filaments" for forecoxal gills -- these

-- which means that I can't go any further: I'd need an electron microscope.

3) And the other thing that was common in the leafpacks was the pronggilled mayfly, Neoleptophlebia.  They were probably N. assimilis, but they're still too small for me to attempt to confirm that ID.

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Sure good to see water again in our streams.  The season's about to pick up.

The caddisfly family Uenoidae is now the caddisfly family Thremmatidae

There has been a significant change of which I've just taken notice.  In our new key for the southeast -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species (South Carolina, 2017) -- Uenoidae is no longer mentioned.  Uenoidae has been changed to Thremmatidae.  I'm not sure when this change occurred; I'm checking on that information.  Thremmatidae, like Uenoidae before, consists of a single genus -- Neophylax.

The keys to Thremmatidae/Neophylax ID are: "Mesonotum with anteromesal emargination; constructing stout case of rock fragments, usually with small ballast stones laterally."  (Larvae, p.292)

On the case in the picture above (Neophylax mitchelli) we can see 4 ballast stones.  The emargination on the leading edge of the mesonotum looks like this.

Another feature of note, the ventral apotome (gular sclerite) is in the form of a "T".

Our new key lists features for 16 species of Neophylax, you may recall that we've found 6 so far in our streams: N. aniqua, N. concinnus, N. consimilis, N. mitchelli, N. oligus and N. fuscus.

I've noted one thing of interest in terms of this change.  In Caddisflies: The Underwater Architects (Toronto, 2004), Wiggins had this to say: "The family Uenoidae now comprises two sub-families: Uenoinae (Farula, Neothremma, and Sericostriata of western North America  with Uenoa of Asia) and Thremmatinae (thremma of Europe, Oligophlebodes of western North America, and Neophylax widespread in North America and eastern Asia).  (Wiggins, p. 187)  It appears as though the sub-family Thremmatinae has been given full family status -- Thremmatidae.

                                                         (Neophylax consimilis)