Thursday, May 3, 2012

Remenus bilobatus -- and Much More: Stonefly Day in Sugar Hollow

I was able to get some really good photos today, so the best is yet to come.  But let's focus on the "new kid in town": the Perlodid stonefly, Remenus bilobatus.  Not the prettiest Perlodid stonefly we see, but then this isn't a beauty contest!  We're trying to track down the Perlodids we see in our streams and note when they appear.

On Remenus, Steven Beaty has this to say:  "Nymphs small, less than 10mm; head with faint M-shale pale mark; lacinia unidentate, with a widely shallow base and with a single, long tooth." ("The Plecoptera of North Carolina," p. 26.)  The "faint M" on the head and the single tooth can be seen in the following photo:

And for a microscope shot of that tooth --

Beaty cautions to leave the ID of Remenus nymphs at the level of genus, suggesting that, in addition to R. bilobatus, two other species might be found by collectors: R. duffeldi and R. kirchneri.  At the same time, he notes that R. bilobatus nymphs "fit the genus description," and that R. duffeldi nymphs remain "undescribed," and R. kirchneri is a species that is still "unknown" in NC though it has been found in adjacent states -- including VA.  Still, until more is known, I see no reason not to call this Remenus bilobatus.  The NC tolerance value for R. bilobatus is 0.9.

I saw a lot of these nymphs on Tuesday, and I saw them last week at South River as well.  I mistakenly thought they were young Diploperlas, even though I knew that young Diploperlas should not be around at this time of year!  Well, we do make mistakes.  (Earlier entries on the genus Remenus were posted on 5/21/11 and 6/2/11.)

Now let's move on to the prettier insects.  I found three different species of Isoperla Perlodids in this gem of a stream: Isoperla namata, Isoperla holochlora, and Isoperla "X" (i.e., species unknown).  Let's start with the unknown.

This is one of two Isoperlas that I found in this same stream last year which Steven Beaty tells me is unknown and unnamed at the moment.  According to information he provided last year, Boris Kondratieff and Stan Szczytko are in the midst of a complete revision of Eastern Isoperlas -- but this study when it's completed will only discuss the adults.  Were we to collect some of these nymphs and raise them in a lab until they hatched as adults, we might connect them with Isoperlas that are already known and named.  There are people who do that  (i.e. collect and raise the nymphs) -- including Beaty and his colleagues in NC.  Can't say that as an amateur I'm that committed.  Maybe some day.  In any event, it's a beautiful nymph.

2. Isoperla namata.  Not a very good photo -- couldn't get the nymph to lift its head.  But I was surprised to find this species around.

3. Isoperla holochlora, pretty common in our streams at this time of year.  This is a young one.

4. One more Perlodid stonefly-- a mature Diploperla duplicata.  Beautiful colors when they're ready to hatch.

5. A common stonefly, Eccoptura xanthenses.  A couple of photos: this was a beauty.

6. And to finish things up -- leaving the stoneflies behind -- a Limnephilid caddis with an eye for color when selecting the stones for its case.

7.  And, of course, at least one spiny crawler.  With those large red eyes, I would guess it's a male.  (The wing pads look like they're ready to pop!)

Note:  (added, 5/1/16).  The stonefly identified as Isoperla "X," is now called Isoperla sp. VA -- still unknown.  And the stonefly I identifed as Isoperla namata was actually Isoperla orata.  It's a species that I've only seen, after this, at the Rapidan River.

And here's where all of these beautiful insects were found --

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