Wednesday, December 29, 2010

Stream Report -- Buck Mt. Creek (+ Black Flies, Pt. 2)

Yes, it was freezing cold this morning, and yes, I had to break through thin sheets of ice moving out from shore into the riffles -- but, the quest for knowledge must go on!  While I found only one small winter stonefly today, and one Taeniopteryx large winter stonefly, I found a lot of Strophopteryx large winter stoneflies (on the two genera, see previous entries).   Most of these nymphs were small, but some are starting to grow and showing their characteristic colors (as the one in the photo above -- live shot).
Has the tide started to turn?  There is always a time when we see fewer and fewer Taeniopteryx nymphs and more and more Strophopteryx nymphs, and perhaps things are moving in that direction.

I also found some netspinning caddisflies, a fingernet caddis, and a fair number of Uenoid case making caddis.  And, I saw a fair number of black flies at this particular site (all genus Prosimulium -- the "good" kind).   But although they were in clusters of 6-8, they certainly were not formed into "colonies."  This is a stream where I have seen large colonies of black flies the past two winters, so this is something I will certainly follow as the winter proceeds.

I thought I might say a word or two about the interesting anatomy of the black fly (full profile view above)  since we see so many of them during the winter.  The photo above makes it obvious why stream samplers call them "bowling pins": they could also be called "velcro butts"!  Black flies have velcro-like projections on their rear ends with which they attach their bottoms to rocks.

They then stand straight up (well, they're slightly bent over) into the current to feed.  In terms of their "Functional Feeding Group" (FFG), they are known as "filter feeders" (or filter collectors), and they collect microscopic bits of food in what look like "bushy whiskers" -- called a "labral fan".  The labral fan is actually quite an elaborate thing, as the reader can see from the photo below (which is looking down from the top of the head).

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