Wednesday, March 23, 2016

Just a beautiful insect: fully mature, Perlodid stonefly, Helopicus subvarians

This morning I was off to Buck Mt. Creek where the water was still pretty high.  Still, it's the time when we find Perlodid stoneflies, and Buck Mt. Creek has proven very productive.

This is Helocipus subvarians, a stonefly that I first identified on 4/2/11.  It's one of the largest Perlodid stoneflies that we find in local streams: this nymph measured 22 mm.  I think I'm right in saying that I've only seen it in Buck Mt. Creek and the Doyles River.  Tolerance value is 1.2.   This nymph is very mature, in fact, I thought it might hatch in my tray while I was taking these photos.
Most striking, how dark the head is both in front of and behind the black transverse band.

On less mature nymphs, even those with dark wingpads, the front of the head is usually orange.  I.e.,

Nice find.  Such rich colors.

My other discovery today was a very small Perlodid stonefly -- ~ 5 mm -- the one we ID at the moment as a variant form of Isoperla orata.

As I've noted before, the patterns of the two (main form and variant form) are quite distinct.  On the variant form of Isoperla orata, there two dark spots behind the ecdysial suture, and the bottom of the notch at the front of the head is straight across.

But on the main form of the species, the dark spots are missing, and the bottom of the notch at the front of the head is rounded.

Also, Isoperla orata is uncommon and only found in very clean mountain streams.  I've never seen it in Buck Mt. Creek, only at the Rapidan River.  And while the variant form can be found side-by-side with the main form, it is also found in streams like Buck Mt. Creek and the upper Doyles River, good streams, but not the equal of the Rapidan River.   For more on this point, see the entry on habitat and species variation posted on 8/26/15.


Hope to get up to Entry Run in Greene County this weekend.  Next week, it's off to Montana!

Wednesday, March 16, 2016

Some pictures from the Rapidan River

Not much to report today.  But I was pleased with these photos, so I thought I would post them.  That's the flatheaded mayfly Epeorus pleuralis.  It's very common at this time of year in cold water streams -- like the Rapidan River.  Fly fisherman, if you're headed that way, take some Quill Gordon imitations.  These nymphs are on the bottoms of rocks, and they're numerous.  Should be hatching now anytime.


E. pleuralis on the bottoms of rocks, and Isoperla montanas crawling around in the leafpacks.  Must be March!  Isoperla montana is part of the "Isoperla kirchneri complex" -- see the entry posted last year on 9/3 --  and it's the most common Perlodid stonefly that I run into: March to mid-April.  While I've never fished the Rapidan River, there must be a prolific hatch of "Yellow Sallies" up here, and it too will be happening soon.


I was really hoping to see a mature Isogenoides hansoni nymph, as I did in March, 2011,

but no luck today.  I'll be back before the end of the month.  It's one of the rare insects that we find in this stream, and I don't want to miss it.

P.S. if you're editing photos with "Photos" on Macintosh, be sure to buy and install the extension "intensify."  I use "Photos" to crop and straighten -- that's it.  "Intensify" is the software to use.

Friday, March 11, 2016

The "rare" one: caddisfly larva, Pseudostenophylax sparsus

This is the second time I've found this species of caddisfly larva.  The first was 6 or 7 years ago at the "Patricia Byrom Nature Preserve" in the Blue Ridge in a very small, very clean stream at high elevation.  But, if you look back to the entry of 3/12/14 you'll see that my friend in Sugar Hollow, has found them in a  tiny spring seep on her land.  Right at the base of this pipe.

This "pool" is 1-2' feet square, and below this you won't see flowing water, just wet leaves and mud.  But that's where this species lives.  Steven Beaty, "The Trichoptera of North Carolina," p. 84: "Occurs in seeps and temporary streams.  A late winter-early spring species.  Rare."  It will hatch as a "Dark brown summer sedge" -- Thomas Ames, Caddisflies, p. 250-251 -- but no trout to eat them in this little pool!

There is only one species of Pseudostenophylax that lives in this part of the country -- P. sparsus.  Pseudostenophylax species are described this way by Wiggins: " all species mesonotal setal areas are confluent through sa1 to sa2 to sa3, and there is a transverse band of setae between the metanotal sa2 sclerites.  Sclerotized parts of the head and thorax are uniform reddish or yellowish brown, broken only by muscle scars.  Abdominal gills are single.  Length of larva up to 16mm.  Larval cases are contructed mainly of small rock fragments, the exterior uniform in outline.  Length of larval case up to 19mm."  (Glenn B. Wiggins, "Larvae of the North American Caddisfly Genera (Trichoptera, 1977, p. 278.

This larva was exactly 16mm; the case, 17-18mm.  For the continuity of the mesonotal setae, this is the best I could do yesterday.

Easy to see the transverse band between the sa2 sclerites on the metanotum.

Not much question about the color of the head.

And yes, the abdominal gills are single.

Beaty adds that the "head and thorax [are] uniformly orangish to yellowish brown with pale muscle scars."  Those pale scars show up nicely on this photo.

A "rare" one -- Pseudostenophylax sparsus.

We also looked for nymphs and larvae in the small, pristine, stream that runs through her land, emptying below into the Moormans.  The leaf packs were LOADED with Peltoperlid (Roach-like stonefly) nymphs.  Other than that, we saw a number of spiny crawlers (probably Ephemerella invaria), and some nice Perlodid stoneflies -- Malirekus hastatis and Isoperla similis.  I took a few pics of the latter.

And on the rocks, as we would expect at this time of year, lots of flatheaded mayflies, Maccaffertium merririvulanum and Epeorus pleuralis, some of the latter already mature.

Good to get out at last.  The weather's improving -- very warm, actually -- so I'm looking forward to exploring the streams.

A note on the photos.  I'm not happy with the quality of the photos I'm posting.  For years, I've used the "iPhoto" software on my Macintosh to edit my photos: it's fast, efficient, and does a pretty good job.  But, Apple has replaced iPhoto with "Photos," for editing pictures.  I don't like it at all!  If you add the extension "intensify" to Photos, the results are better.  I also have "Photoshop Elements 9," which I like.  Unfortunately, "Photoshop" does not work with Apple's new system software (OS 10.11.3, El capitan), an issue that to date, neither Adobe nor Apple seems moved to address (!).  So, bear with me as I struggle to re-learn how to do this.  Maybe with practice...

And here the larva was just peeking out of its case.