Tuesday, March 5, 2013

Nemourid stonefly, genus "Soyedina": a new one for our EPT List

Kudos to my good friend who lives in Sugar Hollow!  On Sunday she and her husband were hiking, climbing up the Blue Ridge near their home.  At a high elevation, she found a small stream and decided to sort through some leaf packs.  And there was this odd-looking stonefly which -- back at their home -- she was able to identify as a Nemourid stonely, genus Soyedina.  That's a genus we have not seen before, and the "EPT List" that I posted on 9/8/12 has been corrected to include this addition.

That means that we have now found three Nemourid genera in local streams: Amphinemura, Prostoia, and now Soyedina.

Amphinemura is fairly common in streams in this part of Virginia: we often see a lot of them in the spring.  The nymphs are not very big -- 5-8 mm -- and they're easily identified by the "cervical" gills at the neck.  This one was found on 4/23/11.

Prostoia nymphs do not have the cervical gills and identification requires microscope work.  The keys to identification are reviewed in my entry of 1/17/12.

I find this genus to be relatively uncommon in the streams I explore.  So far, I've only seen it in the Moormans, Buck Mt. Creek, and parts of the Rapidan River.  Prostoia nymphs tend to show up before the Amphinemuras.  Those pictured above were found in February and March of 2011 and 2012.

The genus Soyedina is described by Beaty ("The Plecoptera of North Carolina, p. 5) in the following way:

Nymphs 6.5-8.5 mm; pronotum with angular corners and a distinct posterolateral notch, with well developed lateral fringe; wing pads divergent; anterior thoracic gills absent.

The "angular corners" of the pronotum and its "well developed lateral fringe" are very clear in this close-up.

The "posterolateral notch" refers to the way in which the sides of the pronotum curve inward towards the rear.

The wing pads are very distinctive in that they seem to move in toward the body before they sharply move out.

This is not a genus we can expect to find often.  Beaty notes that Soyedinas are "found in leaf packs in seeps and small, cold streams," and that "nymphs are typically collected from December to April, mostly in the Mountains."  He adds --- "Relatively rare."  (Beaty, p.5)

The stream in which this Nemourid was found is a tributary to this small mountain stream that cascades down the mountain close to where my friend lives.

I repeat that it's a tributary to the stream in these photos.  It may or may not have water in it year-round.

Great find!
Addendum.  Only two species of Soyedina have been reported so far for Virginia: Soyedina carolinensis (Carolina Forestfly) and Soyedina vallicularia (Valley Forestfly).  (Stewart and Stark, Nymphs of North American Stonefly Genera, p. 217.)

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