Tuesday, April 30, 2013

The "safe" designation: Isoperla montana/ Isoperla n. sp. (new species)

That's the latest word from Steven Beaty.  This is the most common Perlodid stonefly that we see in our streams at the moment, for which I've been using the name Isoperla namata.  That has to change.

According to Beaty, the latest work shows that Isoperla namata is found in the Ozarks and the midwest but not in the East.  However, the nymph of another species -- Isoperla montana -- looks exactly like I. namata, and I. montana occurs in the East from Maine to VA and NC.  Remember that the "montana" in I. montana does not refer to the name of the state; it means this is a "mountainous" insect.  The common name for I. montana is the "montane stripetail."

But there is more to the story.  There is now a third species of Isoperla which produces a nymph with these very same features.  The name for that species is currently being reviewed.  So, for the moment, it's "Isoperla n.sp." (Isoperla new species).   Isoperla montana and Isoperla n. sp. both occur in Virginia and North Carolina.  The nymphs can be distinguished by slide mounting the mandibles and lacinia, but they can't be distinguished from observable physical features (at least, that's my understanding.)

So when we see these nymphs in our streams, we can't be sure if we're looking at Isoperla montana or Isoperla n. sp.  That's where things stand at the moment.    The next generation will be relying on DNA to make these decisions.

(For earlier discussions of the Isoperla namata/Isoperla montana problem, see the entries posted on 2/15/12 and 2/16/12.)

  In 2011, Beaty, referring to this as I. nr. namata, described this species in the following way ("The Plecoptera of North Carolina," p. 24).

I. nr. namata -- nymphs ~ 11 mm; apex of lacinia narrower than base, constricted medially, with row of setae below subapical tooth approaching base;  North Carolina specimens have a dark transverse band on head usually without backward extensions to lateral ocelli but sometimes with extensions and with lighter brown areas behind ecdysial line; abdominal longitudinal lines narrow; abdominal tergites with a transverse row of 6-8 faint dots.

The lacinia looks like this:

Saturday, April 27, 2013

A spring day on two small streams in Sugar Hollow

It's spring, and there are a lot of mayfly and stonefly adults flying around out by the streams.  This female spinner ("imago", a mayfly that's ready to mate and lay eggs) happened to land on my friend's net as I was taking some pictures.  How could I resist?!

The only large mayflies that should be hatching right now in these small mountain streams are Epeorus pleuralis (Quill Gordon), Maccaffertium pudicum (March Brown?), and Maccaffertium merririvulanum.  But this doesn't seem to match any photos we've seen of those insects.  If someone knows what this is, please let us know.  I can imitate adults when I'm fishing; but I can't ID them to the level of species.

Back to the work with which I'm a lot more familiar!  Even these small mountain streams are filled with spiny crawler nymphs at the moment (E. invaria mostly) -- you have to look around to find other things.  But other things there are, so it's well worth making the effort.

1. A beautiful, mature, Clioperla clio Perlodid stonefly.  Absolutely gorgeous!

2. More Perlodids.  The first, an Isoperla holochlora -- small, but note how the wings have already spread -- the second, one of two Isoperlas that we see in these streams: both remain unidentified to the level of species, even by the pros.

3. A fairly mature Ameletid, Ameletus cryptostimulus.  Hmm....could that be our mayfly?  They too will be hatching.

4.  And look at this, there are still lots of Uenoids up here in these high elevation, cold water streams.

1. Neophylax aniqua.  (If you look closely at the first photo, you can see the tubercle on its head.)

2. And Neophylax, species unknown at the moment.  (No tubercle, no clavate gills, head dark brown to black.)

5.  A young, Spike-tailed dragonfly nymph, Cordulegastridae (possibly Cordulegaster erronea).  (Interesting fact -- Cordulegaster is a dragonfly that I've only seen in small, headwater streams.)

6.  A fully mature Epeorus pleuralis.  The bottoms of rocks were covered with them.  (Of course, not all of them were mature -- but many, many were.)

7.  Well, and two spiny crawlers for good measure.  Look to me like E. invaria.


Note:  There is an excellent online key for the identification of Odonata (dragonflies and damselflies) to the level of species.  http://insects.ummz.lsa.umich.edu/michodo/mol/Home.htm.

Thursday, April 25, 2013

Caddis delights at the Rapidan River: "humpless casemaker," Micrasema charonis

In the Rapidan River -- as they are in most of our streams at the moment -- the leaf packs and rocks are filled/covered with two insects -- spiny crawlers (E. invaria and E. dorothea) and Perlodid stoneflies (I. namata, or whatever we want to call them).   That's what I expected to see.

This insect wasn't expected.  This a "humpless casemaker" caddisfly larva (Brachycentridae), Micrasema charonis, and this is the first time I've seen one.  If you're a regular reader, you know that I often see Brachycentrids at the Rapidan River, but in the past, they've all been the "log cabin" casemakers -- Brachycentrus appalachia.  They look like this.  Four-sided case made out of pieces of bark.

So I was surprised and delighted today to see these little cylindrical cases made out of ribbons of vegetation (found two of them).

This is a much smaller insect than B. appalachia.   The B. appalachia case pictured above -- found on 1/4 of this year -- was 15 mm long: The M. charonis cases that I found today were 9 mm, the larvae were only 6.   For identification let's turn to Beaty ("The Trichoptera of North Carolina," p. 80):

M. charonis -- head with distinct dark muscle scars laterally, pale areas anterolateral of frontoclypeus.  Case vegetal and straight.  Mountains and eastern Piedmont.  

lateral muscle scars:

pale areas at front of head:

One other photo is also instructive.  In his genus ID of Micrasema, Beaty notes that the "ventral apotome [is] wider than long."  Our larva nicely flipped on its back for this photo!

So another addition to our EPT list: Micrasema charonis.  TV, 1.0.


But I spotted another casemaker in a leaf pack today, one that we've seen before, the Limnephilid (Northern case-maker) Pycnopsyche scabripennis.

Not the prettiest case that I'ved seen: these larvae just seem to throw these together with twigs and bark.  But note how the larva uses that large piece of bark to cover its head.  This case measured 36 mm (!); the larva inside was 29.  Big insect.

Now for the more common things that we see at the moment.

1. Perlodid stonefly, Isoperla namata (or I. nr. namata, or I. montana).

2. Spiny crawler, E. dorothea (9 mm).

3. Spiny crawlers, E. invaria (both 7 mm).

4. A brush-legged mayfly (Isonychia).  They're starting to mature.

5. And, surprise surprise, another one of those Isoperlas -- the same one that I found at the Doyles River last week -- species still unknown.  Still waiting to hear from Steven Beaty.

This one had lost its left eye.

But the real prize -- Micrasema charonis.

Tuesday, April 23, 2013

The Uenoids found at the upper Doyles River: Identity remains unclear

Steven Beaty was kind enough to examine the Uenoids I found at the upper Doyles River last week and share his findings with me.  The identity remains uncertain.  Most likely, they are Neophylax concinnus or Neophylax toshioi.

The larva lacks clavate gills on abdominal segment 1, but it has lateral gills on segments 2-4.  It also has a blunt, frontoclypeal tubercle which we can see in this microscope photo.

In favor of N. concinnus is the fact that I've found that species lower down in the Doyles earlier in the year.  However, the head of N. concinnus is usually uniform in color -- "uniformly orange yellow to orange brown" (Vineyard, et.al., The Caddisfly Genus Neophylax, p. 11).  The head of our larva is light in the back but dark in the front.

In favor of N. toshioi -- and I'm following Beaty -- is the overall pattern of the head as well as the location of the lateral gills.  Against N. toshioi as the ID is the lack of a pale line on the side of the head from the eye to the base of the mandible -- though such a line could be developing here -- and the fact that N. toshioi is not supposed to be located this far north in Virginia.

So there you have it.  N. toshioi would be an addition to our EPT list, but we can't be sure that's what this is.  Well, what these are since I found two.

Saturday, April 20, 2013

Whoops! Two of those spinys were E. invaria

These are both E. invaria -- not E. dorothea.  This one...

is E. dorothea.

Note the tubercles on the posterior edges of terga 4-7 on that large nymph.

E. invaria and E. dorothea are both in our streams at the moment, and it's difficult to tell them apart without a close view.