Tuesday, June 14, 2011

Tolerance Values, Isoperlas, and Another Trip to the Moormans

Steven Beaty, an Environmental Biologist with the North Carolina Division of Water Quality, has contacted me about a couple of matters, providing information that I thought I would share.
First, North Carolina has recently revised the Tolerance Values it uses for benthic macroinvertebrates. That information is available on their website: http://portal.ncdenr.org/web/wq/ess/bau.  Click on the link for "Tolerance Values for Benthic Macroinvertebrates":
(http://portal.ncdenr.org/c/document_library/get_file?uuid=6cbf48c0-924f-4642-b1d3-3f39aa02185f&groupId=38364): the data is availble in Microscoft Excel format.  Some of the tolerance values I have listed for the southeast are now out of date.

Second -- and of great interest to me -- a revision is currently underway of the naming and identification of the species of the Perlodid genus "Isoperla" in the eastern part of the country.   (Thus, the information provided in my entry of 5/11, must be understood as tentative and "to be revised".)  The revision will focus on Isoperla adult identification -- not on the nymphs -- still, changes in nomenclature can be expected.  This work is being conducted by Boris Kondratieff and Stan Szczytko.

Dr. Beaty has sent me a copy of a draft version (November 16, 2010) of the Division of Water Quality's "Plecoptera In-house Taxonomy Manual," and has granted me permission to use information provided in there in my blog.   I'd like to note at least two things of interest.

1) The nymph identified in my entry of 5/11 as I. namata -- this one --

would be more properly labelled I. nr. namata.   This may be an unidentified species.  While it resembles I. namata, that species is thought to be restricted to the Ozarks and the northeast.  This is an issue that is not yet resolved.

2) The fourth nymph in my entry -- this one --

that I said might be I. holochlora, is called I. nr. holochlora in North Carolina.  It strongly "resembles" I. holochlora, but the head pattern is not exactly the same, and the abdominal banding that is very clear on I. holochlora is not clear at all on this nymph.  (I'll provide a photo of an I. holochlora nymph that I found today later on.)

(The Isoperla nymphs that were numbers 5 and 6 in my entry of 5/11, by the way, are being studied by Dr. Beaty, and I will let you know what he tells me about identification.   The photo at the top of the page is of one of those nymphs -- one that I found today.)

So, stay tuned for more on this very interesting genus.  Dr. Beaty comments that some regard North Carolina (and presumably parts of Virginia) as "the epicenter of Isoperla diversity in the world."


Today's report.  I went back to Sugar Hollow today to a superb stream that flows into the Moormans.
I was last here on 6/2, and the insects that I found today were much the same as I found on that trip (you might want to look again at that entry):  lots of baby Roach-like stoneflies -- they were scurrying all over the place -- and lots of baby Giants.  I did find one thing that I wasn't expecting to see.

It's a Lepidostomatid case-maker!  I associate these with the winter.  But, I saw three of them today -- and it's the middle of June!

For the rest of my findings let me just provide you with pictures.  (Keep in mind that the "mystery" Isoperla at the top of the page came from today.)

1. Free-living caddisflies -- I saw at least four, three of them long (1"+) and fat!  I found three different colors, so I'll show you all three.

2. Peltoperlids (Roach-like stoneflies).  I did find a couple mature ones that still haven't hatched in addition to the hundreds (literally) of babies.

3. And finally, the genuine I. holochlora, this one pretty mature.  Note how the yellow area on the front of the head is confluent with the labial suture (the yellow line that crosses the front of the head) on I. holochlora -- not so on I. nr. holochlora (pictured above).   Also note the dark abdominal bands.

I saw very few mayflies today -- a few small flatheads, probably genus Leucrocuta.  I expected to see some Epeorus vitreus nymphs (picture of one from Buck Mt. Creek below), having seen so many Epeorus pleuralis here in the spring, but I did not see a one.

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