Saturday, January 26, 2013

On Vacation: A Few Days in Sunny Florida

Bucolic Virginia -- on the way to Buck Mt. Creek with the Blue Ridge in the background.

I'll return to the streams next Friday -- February the 1st.  No photos of aquatic insects till then -- unless I run into a stream on a golf course, or while I'm fishing out in the ocean!

Thursday, January 24, 2013

The small minnow mayfly Heterocloen amplum: the "odd man out" of the genus

I went to the Doyles yesterday looking for the nymph in the photo above, but all I found was water that was starting to freeze right down to the bottom!  22ยบ -- I should have known better.  But this photo will do.  This H. amplum nymph was found in the Doyles on February 6th of last year.  You may recall that I found a small H. amplum here last month on 12/21.  This one:

Heterocloeon amplum is a small minnow mayfly that I associate with the winter: I see them in a number of streams from late December into the beginning of April.  They show up in good numbers in Buck Mt. Creek and the Doyles, but I see them as well at the Lynch River, the Rapidan River, and even in the North Fork of the Moormans.   It's the biggest small minnow mayfly I've seen, measuring 7-9 mm, so fly fishermen should enjoy this early hatch of the "Blue-winged Olives."

If you look back at some of my earliest postings (early 2011), you'll see that I originally identified this as genus Baetis -- then I thought it might be Acentrella.  It took me awhile to identify this one correctly.  But in my defense, Steven Beaty ends his discussion of H. amplum with the following note: "Known previously as both Baetis ampla and Acentrella ampla."  ("The Ephemeroptera of North Carolina," p. 9.)

The truth is, it just doesn't fit well into this genus -- Heterocloen.   Of the two-tailed Baetids described in Barbara Peckarsky,, Freshwater Macroinvertebrates of Northeastern North America, pp. 33-36),  Heterocloen is defined by using the following features: "Center region of gills with a large pigmented area; procoxae with a single filamentous gill on inner margin."
Neither of those features is found on H. amplum nymphs!  In fact, those features are true of only one of the species that we find in this genus -- Heterocloeon curiosum.  The Peckarsky book is somewhat out of date and must be used with caution.

Let's take a closer look at this genus, using, as I normally do, the descriptions given by Steven Beaty (p. 9).  First, Beaty notes that the genus is divided into two different groups: Heterocloeon (Heterocloen) and Heterocloeon (Jubilatum).   Beaty notes four species that belong to the first group: H. berneri, H. curiosum, H. frivolum, and H. petersi.  All of the species that belong in this sub-genus have something in common: they all have "forecoxal" or "procoxal" gills.  These gills are tiny, finger-like gills that stick out from the base of the front legs.  They look like this:

Only two members of this sub-genus have been found in North Carolina, H. curiosum and H. petersi, species that I've found in our streams as well.   (H. berneri is reported from South Carolina and H. frivolum from Tennessee).

H. curiosum is common: I see these nymphs in large numbers in the Rivanna River each summer.  And as I noted above, they're a perfect fit for the description that Peckarsky provides for the genus as a whole: they have gills with pigmentation in the center, and they have procoxal gills.  They are also sexually dimorphic -- i.e. males and females have different colors and patterns.  The gill pigmentation is clear in all of these pictures.



And if you get lucky and get a close-up of a nymph turned upside-down, you might see the forecoxal/procoxal gills!

H. petersi is not as common as H. curiosum: to date, I have only found one nymph -- that too was in the Rivanna.

H. petersi nymphs also have forecoxal gills, but the abdominal gills do not have center pigmentation.  Rather, Beaty describes them in the following way: "gills grey or grey-brown with light margin."  Beaty also notes that H. petersi is distinctive in having "no dorsal pattern" on the abdominal terga.  You can see both of those features in the following photo.

The nymph in these photos is clearly a male -- note the large eyes.  But since I've not yet found a female, I can't tell you if this species too is "sexually dimorphic."  That is something that's true of Heterocloen amplum.

So let's look at this "odd" one.  H. amplum is the only member of the sub-genus Jubilatum that Beaty describes.   It has very little in common with other members of this particular genus.  Like all Heterocloeons, H. amplum nymphs have two caudal filaments (tails) and normally hind wing pads are present -- but that's about it.   They do not have forecoxal gills, and they do not have gill pigmentation.  Even the denticles on the claws differ from those that Beaty cites for all genus members: "claw usually with 2 rows of denticles with 1 row being long denticles and the second row being small, squarish pegs (400X magnification required)."  H. amplum claws do not fit this mold: "1 row of denticles becoming progressively longer and a secondary ridge without denticles."

H. amplum nymphs like H. curiosum (and possibly H. petersi) are sexually dimorphic, so perhaps that's a feature in common.



But let's read the full description of the species H. amplum.

H. amplum -- nymphs 7-9 mm; unique labial palpi parallel sided; shortened leg setae; femora, tibiae and tarsi relatively shortened, tarsi slightly dilated apically with wide, pale medial band; gills large, suboval, with rudimentary trachea.  (Beaty, p. 9)

1) labial palpi, parallel sided:

2) shortened leg setae:

3) femora, tibiae, and tarsi relatively short (clear from the photos above):

4) tarsi dilated apically with a wide, pale band:

5) gills suboval with rudimentary trachea. (Actually, in the sunlight we can see a thin central stem that runs through the gill from which very fine filaments branch out to the edges).

And we can also see -- without a 400X microscope -- the denticles that are characteristic of the sub-genus Jubilatum.

They do, indeed, become "progressively longer."

Heterocloen amplum, especially when we look at those claws and note the lack of procoxal gills, neatly fits into the sub-genus (Jubilatum) ID.  So, I guess the question I have is what is it that ties the two sub-genera together?  I can't see what it is, but I guess the entomologists know.  When I look at the three species of Heterocloen we find in our streams, I can cleary find common ground between H. curiosum and H. petersi, but for me H. amplum sort of stands on its own as the "odd man out" in this genus.

Here's Beaty's full description of the genus Heterocloeon.

Genus Diagnosis: Forecoxae usually with a single filamentous gill or protuberance (osmobranchia); tergal scales absent; claw usually with 2 rows of denticles with 1 row being long denticles and the second row being small, squarish pegs (400X magnification required); hind wingpads usually present; two caudal filaments.

Features that are italicized in this description are considered to be crucial.

Maybe more should be made in the keys of the common shape of the gills.  Were the grey pigment removed from the gills of H. curiosum, the gills of our three species would look much the same: "gills large, oval, with rudimentary trachea."

Wednesday, January 23, 2013

More on the tubercles on the Uenoids N. aniqua and N. mitchelli

I took some microscope photos this morning that might clarify the points I've been trying to make about the tubercles (median frontoclypeal -- middle of face) on the Uenoids that I've been finding, those I think are Neophylax aniqua and Neophylax mitchelli.

Remember Beaty's descriptions --

N. aniqua -- "prominent tubercle on head, often semi-blunt."  That's the larva in question at the top of the page: here's a close-up of the tubercle on the head of that larva.

N. mitchelli -- "long pointed tubercle on head, usually directed somewhat posteriorly."  Here's another shot of that larva,

and here's a close-up of the tubercle on its head.

They're very distinct.  And there's another difference I've noted in the larvae that I've found so far:
the head, pronotum, and mesonotum of what I think is N. aniqua is uniformly dark brown; those of N. mitchelli are much lighter in color.

N. aniqua, 1

N. aniqua, 2

N. mitchelli, 1

N. mitchelli, 2

If I need to correct this, I'll let you know.  But those tubercle photos might prove to be useful.

Tuesday, January 22, 2013

And to finish up that report...

This is where I was yesterday -- is it any wonder that I find wonderful insects in this kind of stream?   And I did find wonderful insects.  Within an hour, I had collected Peltoperlids (Roach-like stoneflies); Chloroperlids (Green stoneflies); Perlodids (Malirekus hastatus, Diploperla duplicata -- and others to be ID'd); Giants (P. proteus, all sorts of sizes); Leuctrids (Rolled-winged stoneflies); Pronggilled mayflies; Ameletid mayflies; and Flatheaded mayflies (Maccaffertium pudicum, Maccaffertium merririvulanum, and Epeorus pleuralis) -- and more.  And there were the Uenoids (Neophylax mitchelli -- see yesterday's posting -- and Neophylax aniqua) and the Limnephilids (Northern case-makers).

Then I slipped, tipped my bowl, and lost everything that I had collected!  So I started over again but was contented with less, deciding to focus on the case-making caddisfly larvae.

1. The Limnephilid, Pycnopsyche gentilis.

I saw a lot of them -- but this one seemed like the best subject for photos.  I'll have to check my records on this, but I think that P. gentilis is the only Northern case-maker I've seen in these small mountain streams.  In early instars, it usually makes this kind of case -- a three-sided case made out of trimly cut sections of leaves which then overlap one another.    In later instars, you may remember, they normally switch to a case made of pebbles which are firmly cemented together.   In this photo taken in May of 2011, we see a case that's in transition.

This is a sizeable insect, reaching lengths of 20-22 mm (Beaty, "The Trichoptera of North Carolina," p. 84).  But the one in yesterday's photos was about 10 mm in a case that measured 15.   The tolerance value is 1.8.  Trout, by the way, will eat them case and all!  But I've never seen any trout in this little stream.

2. Uenoid caddisfly larva, Neophylax aniqua.

For more detail on this species, look at Saturday's posting.  A friend has reminded me that it's risky to ID an immature larva, so my ID is a tentative one -- but I feel pretty certain about it.  This larva was 4-5 mm in a case that was 6.

You'll recall that the key features in this species ID are 1) the lack of clavate gills on abdominal segment 1; 2) lack of lateral gills; and 3) a stout, median frontoclypeal tubercle that does not point to the rear (like that of N. mitchelli).   If you look closely at this photo, you can see the tubercle on top of the head...

But it shows up much better in these microscope views.

In this last photo, the clavate gills are conspicuous by their absence.  I.e., you don't see these (photo of Neophylax consimilis):

In the North Carolina list of tolerance values, N. mitchelli is rated 0.0; there is no rating given for N. aniqua.   But it's probably a very intolerant insect.  Remember that it is common to find N. mitchelli and N. aniqua in the same types of streams (first order streams; headwater streams).

Just a few other photos.

3. The flatheaded mayfly, Maccaffertium merririvulanum.  I managed to find another one after dumping the first!  Note the pale "V's" on the tergites.

4. A Leuctrid that I found on Saturday but didn't bother to post.

5. And this is what the Malirekus hastatus Perlodid stoneflies will look like when I get some good photos!


Off to the Doyles River tomorrow -- if I can put up with the cold!

Monday, January 21, 2013

Whoops! Make that Neophylax mitchelli, not Neophylax ornatus

I hate making mistakes -- but I've done it again.  Then again, making mistakes is often the way that we learn.  The Uenoid that was featured in the previous entry was Neophylax mitchelli, not Neophylax ornatus.

This morning I returned to Sugar Hollow and went to my upstream site on one of my favorites streams.  I again found two different Uenoids -- among other things -- including the one in the picture above and the pictures below.

When I saw this in my microscope when I got home, I said "Aha!" another N. ornatus.  The face was yellow to brown, it had clavate gills, and there were muscle scars at the back of the head.  But then I noticed a problem -- it had a tubercle on its head.  Look again at our second photo:

Neophylax ornatus does not have a median frontoclypeal tubercle, but N. mitchelli does.  It has a tubercle that's thin and pointed and one on which the tip points back to the rear.    Let me show you some photos on which I hope that feature is clear.  (Click on the photo to enlarge it.)

I wish those photos were better -- but that's the best I could do.   This larva -- and the one that I found on Saturday -- is Neophylax mitchelli.  On N. mitchelli, Beaty ("The Trichoptera of North Carolina,"  p. 87) has the following things to say.

N. mitchelli -- well developed clavate ventral gill on abdominal segment 1; long pointed tubercle on head, usually directed somewhat posteriorly.  Case often smaller and more fragile than other Neophylax species.  Mountains only.  Common.

In the following photo, you can see the clavate ventral gills (at the least the one to the left), and get another glimpse of the tubercle on the head.

So, the Uenoids I'm finding at high elevation in the Blue Ridge are N. mitchelli and N. aniqua.

I'll post a complete report on today's trip in an entry tomorrow.  I found all sorts of things in this wonderful stream, including another N. aniqua, and my first Limnephilid (Northern case-maker) of the season: Pycnopsyche gentilis, the one that makes the three-sided case out of pieces of leaves.