Wednesday, December 15, 2010

Stream Report -- Mechunk Creek

The water is very cold -- air temperature this afternoon of 35 degrees -- but with snow in the report for tomorrow, I decided to see what I could find in Mechunk Creek (to the east of Charlottesville).  Lots of stonefly nymphs, no mayfly nymphs.  And most of the stoneflies were in leaf packs -- not on the bottoms of rocks.  Large winter stoneflies (genus Taeniopteryx) were numerous, with just a few small winter stoneflies around.   I also found, as I did last week at Buck Mt. Creek, some tiny large winter stoneflies of the genus Strophopteryx (see photo above).   And there were a few Perlodid stoneflies (genus Clioperla), which are actually getting quite big (picture of head enclosed).

The big surprise was that I found huge numbers of black fly larvae for the first time -- large colonies on every single rock that I lifted (it's really a sickening sight!).  They were also in the leaf packs.  However, in every case they were genus Prosimulium -- the "good" (less tolerant) black fly.   We found large numbers of black flies here in the spring (May), but they were all genus Simulium.  (For the distinction see the previous entry.)

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