Thursday, May 12, 2016

Tough conditions -- but an important discovery

Horrible weather!  Rain, clouds, fog, day after day.  But I had to get out of the house.  So, I ventured out to the Upper Doyles River to see what I could find.  Finding insects wasn't a problem but taking photos was a different matter completely.  I took 59 photos today -- I kept 3 to edit.  I sure hope they're right about the sunshine this weekend.

Above, one of the photos I kept and cleaned up a bit.  The "brushlegged" mayfly, Isonychia.  Beaty says we should leave this at the level of genus.  ("The Ephemeroptera of North Carolina," p. 15)  I had 3-4 of these in my net, all of them like this one, very dark = very mature.  These nymphs tend to hatch in June and July in our parts.  Early on, they look more like this.


Another one of my photos, the Perlodid stonefly Remenus.

I believe I've noted before that this is the last Perlodid I see at the end of each season.  We start to see them, end of April/early May, and they hang around until June/July.  Hate to say it, but it's a thoroughly boring Perlodid -- not much to look at in color or pattern.  Alas.  Remenus is the Perlodid with the lacinia that's "unidentate" -- one tooth.


This is the third photo I kept.

It's a terrible photo, but I wanted it for documentation.   Isoperla orata, and this is the first time I've seen it outside of the Rapidan River.  Note the distinctive abdominal pattern: the pale areas on the abdominal segments are completed surrounded by a dark border.

This species was first described by Frison in his work, "Studies of North American Plecoptera," Natural History Survey Division: Bulletin, 22:2, September, 1942, pp. 323-325.  On the abdominal pattern he said, "Longitudinal dark stripes on abdominal tergites tend to be connected on hind margin of segments by narrow transverse line which gives tergites somewhat the appearance of having cell-like light spots each side of median, longitudinal stripe."  Bingo.  Here's one that I found in late May at the Rapidan River: they'll be maturing real soon.

Until today, I had only found the variant form of this species at the Upper Doyles River, the one on which 1) the median line on the tergites is much more pronounced and 2) the pale spots do not look like cells.  This one.

So at the Doyles River, as at the Rapidan River, the two forms co-occur.

Praying for sun!

Oops!  I totally forgot.  A few weeks ago, I was going back through my files and found this.

It's also Isoperla orata, and this one was in one of our small headwater streams in Sugar Hollow!  May 2, 2012.  Guess it's in more of our streams than I thought.

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