Sunday, December 26, 2010

Moormans River off Sugar Hollow Road -- report

I found a number of large winter stoneflies -- both Taeniopteryx and Strophopteryx -- including this very orange specimen (Taeniopteryx).  But small winter stoneflies far outnumbered the large.  The small winters in this particular stream were very small and immature, in contrast with what I've been finding in streams like Buck Mt. Creek (and elsewhere).  Why?  I suspect it has to do with the fact that the Moormans is very close to, or in, the Bude Ridge Mountains.  All fly fisherman know that a hatch always begins in the lower part of a stream then gradually moves upstream.  Thus, we might expect to find insects in earlier instars when we get this close to the source of a stream.  Is this because the water is colder upstream and food sources diminished?   In addition to the winter stoneflies, I found one Perlodid stonefly (genus Diploperla) and two Perlid (Common) stoneflies (genus Acroneuria).  All of the stoneflies were in leaf packs.

I found only one mayfly: this very small Spiny Crawler (Ephemerellidae: actual size, about 1/8").  While it's hard to determine genus in this early stage, I suspect this is Ephemerella:  we find huge numbers of Ephemerella Spiny Crawlers in our streams throughout the spring, most hatching by the end of May.  I also found one black fly -- genus Prosimulium.  All of the black flies found in this stretch of the Moormans in early November were genus Simulium (on the difference between the two genera, see the earlier entry on "Black Flies".

On the bottoms of rocks, I found Uenoid caddisflies, common netspinner caddisflies, and a couple of Saddlecase maker caddisflies.  One of these is pictured above: upper left shows the ventral side of the case, with the head and tail of the larva sticking out from the ends (hanging over the "saddle"); lower right is the dorsal view of the case.  When the case is attached to a rock, the caddisfly cannot be seen.  Stream samplers rarely get to see this caddisfly in its case.  When distrubed, it quickly abandons its case. Thus the larva alone shows up on the net (closeup of the larva below).   The Saddlecase maker is the only case making caddisfly to abandon its case and build a new one as it passes through instars, getting larger and larger.  Most case makers simply add material on their cases.

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