Thursday, December 15, 2016

The Uenoids (little northern case-makers) at Buck Mt. Creek: at the bottom on the "longitudinal gradient"

At Buck Mt. Creek yesterday I collected a couple of Uenoids to photograph.  I assumed they would be the same species: that turned out to be wrong.

Let's start with the larva at the top of the page.  It's been awhile since I worked on Uenoid identification, but I still remembered the key features we have to examine.  They are: 1) the presence or absence of a tubercle on top of the head (also it's size and shape if present); 2) the presence or absence of "clavate" gills; and 3) the number of setae at the sa3 position on the first abdominal segment (ventral).  E.g.,

This larva lacked clavate gills, and I did not see a tubercle.  The setae count at sa3 came to 6-10.  Here's the view.  Note that they're also long and thick.

Of the species I've found so far in our streams, that sounded like Neophylax fuscus.  (See R.N. Vineyard,, The Caddisfly Genus Neophylax, Royal Ontario Museum, 2005, p. 24.  "Frontoclypeus lacking median tubercle,""Abdominal segment I with ventral sa3 bearing 6-9 relatively long stout setae; segment I lacking [clavate] gills.")  Sounds like a match, so I looked to Steven Beaty for confirmation.  There we find "N. fuscus -- without clavate ventral gills on abdominal segment 1; large blade-like spines on anterior pronotum; head dark brown to black with light muscle scars.  Occurs in northeastern Mountains and clean headwater streams to the Tar River. ... Relatively rare." ("The Trichoptera of North Carolina," p. 87)  I was unable to get a good view of the front of the pronotum, but the muscle scars on the head were easy to see.

I feel pretty good with that ID: Neophylax fuscus.

How about number two?

With the microscope I could see that this larva too lacked clavate gills, and I couldn't see any tubercle.  I thought it was just the same species.  But then I counted the setae at sa3 -- only 4.

That takes fuscus out the running.   My next guess was concinnus, and I think that's what it turned out to be.  Beaty says very little about N. concinnus: it has yet to be found in NC.   For the full description -- more than I'm going to cite -- we go to Vineyard, (p. 46) where we read, "Abdominal segment I with ventral sa3 each bearing 2 to 4 setae, segment I lacking gills."   They add "Head relatively uniform in colour."  And they also say "Frontoclypeus often with short median tubercle."  The tubercle is indeed short: I didn't see it until I turned the larva the right way.

Now, I've found N. fuscus at this location before (see the entry of 12/27/13), along with N. oligius -- this one.

So with N. concinnus we now have three different species in the same spot in the same stream.  This is very interesting in terms of what the authors of The Caddisfly Genus Neophylax call the "longitudinal gradient of species" (p. 24).  Of N. fuscus they note that "it always occupies the farthest downstream zone in the longitudinal gradient of species."  I've talked about this Uneoid sequence before (12/28/13) so let me just cite my own words.

"1. Neophylax aniqua
 2. Neophylax mitchelli
 3. Neophylax consimilis
 4. Neophylax oligius
 5. Neophylax fuscus

That sequence, as it turns out, corresponds to the Uenoid continuum that I've noted so far in our streams.  That is to say -- as you move downstream from a headwater stream to a second or third order stream, you might find Uenoids all the way down, but you'll find different species.  Thus, when I go to my favorite small mountain stream in Sugar Hollow -- a first-order, headwater stream -- and go to the highest part of that stream, I find N. aniqua and N. mitchelli.  When I move down that stream to a site not far from the Moormans, I find N. mitchelli and N. consimilis.  When I go to the South River up in Greene county, the Rapidan in Madison County, and the upper Doyles River, all second-order streams, but streams that are still in the mountains, I find only N. consimilis.  And when I go to the lower Doyles River and Buck Mt. Creek, second order streams that have moved out of the mountains and into field country, I find N. oligius and N. fuscus."

When I wrote this, I had not yet found N. concinnus.  But I did find one just a few weeks after that (1/9/14).  This is a species we'd expect to find between our upstream species (aniqua, mitchelli, consimilis) and those further down (oligius and fuscus).  But I'm not at all surprised that we've found it in Buck Mt. Creek.  Of N. concinnus, Vineyard note "Neophylax concinnus occupies a wider array of habitats than any other single species in the genus, ranging from small springs and cold headwater streams to warm medium-sized rivers.  It is generally found in small second- and third-order streams."  Bingo!  That's Buck Mt. Creek.  (Our location in springtime.)


I'll be looking closely at our Uenoids this year.  I'd really like to find a species we've not found so far: N. ornatus, a species that "occurs in 1st order Mountain and Piedmont streams".  (Beaty, "The Trichoptera of North Carolina," p. 87)  It has been found in Virginia -- the Blue Ridge Mountains in Nelson and Madison counties.  No reason it shouldn't be in Albemarle county as well.

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