Friday, December 19, 2014

The "odd" Lepidostomatid: back to Sugar Hollow's small streams


What's wrong with this picture?  Well, that appears to be a Lepidostomatid (genus Lepidostoma) larva in a 3-sided case made of pieces of leaves, and as Wiggins has told us, Lepidostomatid cases "are usually four-sided and constructed of quadrate pieces of bark or leaf." (Glenn B. Wiggins, Larvae of the North American Caddisfly Genera, 1977 [1st edition], p. 156)  They can also, when very young, make cases out of sand grains, and we also find cases that combine the two construction techniques.  So,  we find these


and these


and these


What does make a 3-sided case out of pieces of leaves or bark?  The Northern case-maker, Pycnopsyche gentilis.  This one


Our Lepidostomatid is in the wrong kind of case.  I'm not sure what to make of this find: it could be a matter of species.  Wiggins adds "Final instars in some...species assigned to Lepidostoma have cases of plant materials placed spirally or transversely" (p. 156) so there may be some odd cases around.  In any event, This larva cooperated for some very nice photos, despite it's very small size (about 5 mm).





By the way, I did find other 3-sided cases this morning that did contain P. gentilis larva.  This case for example.


I kept both of the cases you see in these photos, and here's what I found when I looked into my microscope tray.


Very curious!
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I spent the morning at the small stream in Sugar Hollow that runs through a friend's land high above the Moormans.


 The water was low, but we had no trouble finding interesting insects.  Some other photos to look at.

1. Perlodid stonefly, Malirekus hastatus.  This is a "killer," and this one ate one of my Roach-like stoneflies the moment I glanced away?



2. Roach-like stonefly, genus Peltoperla.  Only saw three or four.



3. A "Weighted-case maker": Goera calcarata.  Beautiful case.



4. And last but not least, a "normal" Lepidostomatid in a case made of sand: one of the smallest I've ever seen.


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Back up here in the winter -- but we'll be needing some rain.

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Postscript:  On reflection-- I suspect that our "odd" Lepidostomatid had simply moved into a P. gentilis case that had been abandoned.  It happens.  Seems the most likely explanation.

Wednesday, December 17, 2014

All the evidence we're going to need: That's Acroneuria lycorias in Buck Mt. Creek


I expected to see winter insects today at Buck Mt. Creek -- and I did: small winter stoneflies, large winter stoneflies (still very tiny), Clioperla clio (only one), Uenoids, and Glossosomatids (Saddle-case makers).  But everything that I saw was covered in silt after heavy rains yesterday.  So, I didn't take a whole lot of pictures.

However, I did find three more Acroneuria lycorias/carolinensis nymphs (look back to the previous entry), so I had a chance to test out my theory.  I argued last time that the A. lycorias differed from A. carolinensis in two different ways: 1) yes, they have anal gills while carolinensis do not, and 2) vs. carolinensis, they lack medial markings on the terga (dashes, a stripe).  All three of the nymphs from today can be used for support of that thesis.

The biggest of the three: 16 mm.



Take a close look at that photo.   No need for a microscope to see the anal gills on this baby, and there are no medial markings.


Here's one that was smaller.  But you can still make out the gills, and note that the tergal bands are fairly regular, something we noted last time.



Beaty does not use the lack of medial marks/stripes to distinguish lycorias from carolinensis.  Have to pass this data along and see what he thinks.
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One other insect of interest this morning: the small case-maker Apatania incerta, one that I don't find very often.



Terrible photos -- best I could do.  Still, we can see the features that are characteristic.  1) the case is "cornucopia" shaped with a hood at the top that covers the head of the larva as it's crawling along; and 2) the larva is yellow in color.  But "proof" requires a microscope view.



The front edge of the mesonotal sclerites are straight across -- vs. those of the Uenoids which are "emarginated."  And there are no sa1 sclerites on the metanotum: in their place we find a setal row:   ("anterior metanotal plates replaced by row of about 20 setae" (Beaty, "The Trichoptera of North Carolina," p. 85.)

I'll be seeing totally different insects on Friday: off to one of my favorite small streams in Sugar Hollow.
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(P.S.  Steven Beaty confirms that there seems to be something to the correlation we've noted: presence or absence of anal gills, presence or absence of medial, abdominal markings.  How about that?  We may be on to something.)

Thursday, December 11, 2014

Acroneuria carolinensis, Acroneuria lycorias: How to tell them apart


At the risk of trying your patience, I want to assert in this entry that it is possible to distinguish the nymphs of Acroneuria lycorias and Acroneuria carolinensis, even if the experts these days are hesitant to take a firm stand on the issue.   The nymph in the photo at the top of the page is Acroneuria lycorias: I found it at Buck Mt. Creek on 10/28.  This nymph,


I'd argue, is Acroneuria carolinensis.  It was found at Entry Run on 11/30.
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You'll recall from previous entries (10/23, 10/28, and 11/30) that at issue in telling the two species apart is the presence or absence of anal gills.  T.H. Frison (Studies of North American Plecoptera, 1942, pp. 282-284) had argued that A. lycorias has them, A. carolinensis does not.  However, Beaty waffles on this, noting that on A. carolinensis nymphs "anal gills [are] usually present," while on A. lycorias nymphs "anal gills [are] usually absent, sometimes small."  (Beaty, "The Plecoptera of North Carolina," p. 14.)  The word "usually" (italicized by me for emphasis) sort of muddies the waters.

I want to argue that I've found both species -- that I can prove it -- and my arguments on this are three.

1. Every nymph that I've found that I regard as Acroneuria carolinensis has lacked anal gills.  I preserved the nymph from Entry Run.  Have a look for yourself.  ("Paraprocts" are the lobes adjacent to the anus.)


The only nymph that I've found that I regard as Acroneuria lycorias has them.  They are quite clear on the nymph found at Buck Mt. Creek.  (But you can't see them from the front.)


2. A. carolinensis nymphs, with a tolerance value (North Carolina) of 1.2, should only be found in very good streams: A. lycorias has a TV of 2.1; I would not expect to find the two together -- and I haven't.  As I've noted before, I find A. carolinensis in very clean mountain streams: the Upper Doyles River, not far from the SNP, and Entry Run which is in the Blue Ridge.    Buck Mt. Creek, home to my A. lycorias nymph, while still very good water, runs through fields and pastures.

3.  While I've made points 1. and 2. in previous entries, this one is new.  While it is true that the nymphs of both species look almost exactly alike, they differ in one significant way.  Look closely at the abdomens.

Acroneuria carolinensis



Acroneuria lycorias


Note 1) that the bands on the terga of the carolinensis nymphs are very irregular/wavy; those on the lycorias nymph are not.  They are almost uniform in thickness.  And 2) on carolinensis, there are medial extensions of the dark bands that in some nymphs actually turn into a longitudinal line.  There are no such extensions on the lycorias bands.  (Also of interest, I think, is that odd shaped medial extension on tergite 10 on the lycorias nymph.)

This is why I think that this is important.  Frison includes illustrations of A. carolinesis and A. lycorias nymphs in his study (pp. 282-283), and bingo, we can see the same distinct abdominal patterns on the two nymphs!  His nymphs look exactly like those in the pictures above.
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Acroneuria carolinesis



and Acroneuria lycorias


I think we can tell them apart.

Sunday, December 7, 2014

No unusual insects -- but a very special stream


Sugar Hollow: one of the small streams I've explored -- but one that I've been to only two or three times.  It remains the only stream in which I've found the small winter stonefly, Paracapnia angulata.  It cuts a deep defile as it cascades down the side of the mountain, leaving lots of boulders on both sides of the stream.


(That photo almost cost me $600.00: I dropped my iphone into the water right after this shot!  It seems to be okay.  Close call.)

It was no surprise to find lots of Roach-like stoneflies (in the picture at the top of the page) in the leaf packs.  They're common all winter in these small mountain streams.  I don't usually keep them for photos, but I continue to look for a genus I know to be here -- my friend has found it -- one that I still haven't seen: Viehoperla.  It's one that, according to Beaty, "Occurs in undisturbed, small, cold streams..in the Mountains from spring through early fall,"  but it's "rarely collected" ("The Plecoptera of North Carolina," p. 13).  It differs from Tallaperla and Peltoperla (both of them common out here) in that the "thoracic gills [are] single." (Beaty, p. 13)

This one appears to be Tallaperla -- the thoracic gills are double.

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Still common on tops of the rocks in still water pools -- "Weighted-case makers" -- Goera calcarata.  I photographed two that had very nice cases.



A nice view of the sharp point of the anterolateral projections of the pronotum, and a good look at the mesonotal anterolateral projections.

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Lots of common stoneflies around: Acroneuria abnormis and Eccoptura xanthenses and a couple of Leuctrids -- but still too early to find the Paracapnia small winters.  Back in January for that.


Sunday, November 30, 2014

Back to Entry Run -- and one more time on the Acroneuria carolinensis/lycorias issue


Safely back from Entry Run: apparently no one thought I looked like a deer (!)

I found a fair number of Perlids -- common stoneflies -- this morning, and most looked like the one in the photo at the top of the page, which I think is Acroneuria carolinensis.  But you'll recall that this ID is an issue (see the entries from 10/23/14 and 10/28/14).  Acroneuria lycorias nymphs look exactly the same.  And while Frison says they can be distinguished by the presence (lycorias) or absence (carolinensis) of anal gills, Beaty argues the distinction isn't that clear.   According to Beaty (in one of the e-mails he sent me), they have found both types of nymph (with and without the gills) in the very same water, so they're not sure that the gills are a real point of distinction.  However, in that same e-mail he told me that if every nymph that I find in the same section of the same stream has them or lacks them (anal gills) then I can probably feel certain about the ID.

The nymphs that I found this morning did not have anal gills.  The nymphs that I found in the upper Doyles River -- similar water to Entry Run -- on 10/23 did not have anal gills.  Every nymph in my reference vial -- and I think they're all from the Doyles -- lacks gills.  I have only found one of these nymphs with the gills -- the one I found on 10/28 at Buck Mt. Creek.  This one.


And these are the gills.


Acroneuria carolinensis has a tolerance value of 1.2; Acroneuria lycorias has a tolerance value of 2.1.  Entry Run and the upper Doyles River are both very clean mountain streams, both of them in or near the Blue Ridge: Buck Mt. Creek, while being a very good stream, runs through farm land away from the mountains.   Pretty clear where I'm going: I think we've got A. lycorias in Buck Mt. Creek but A. carolinensis in Entry Run and the Doyles.   That's my working hypothesis at the moment.
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More photos from Entry Run.

1. More pix of two of the A. carolinensis nymphs that I found this morning.





2. A "weighted-case maker" (Goeridae): Goera fuscula.  They're still around.


Note the sternal plates -- one of the features that helps us with the species ID.

3. A spiny crawler mayfly -- first of the season: Ephemerella invaria (the one with tubercles on the rear edges of the terga).


4. Giant stonefly: Pteronarcys proteus.


5. And another "first of the season," a Uenoid case-maker: Neophylax consimilis.