Sunday, May 15, 2011

A Quick Look at Some Streams: the Lynch River and Ballinger Creek

Those of you who live in cenrtral Virginia know what a gray, dismal, drizzly weekend it's been.  So, I could sit around and twiddle my thumbs, or go out to some streams, even though, because of the dark skies, I despaired of getting any good photos.  Yesterday, I took a quick trip to the Lynch River, and this morning I headed down to Ballinger Creek (Fluvanna County).  My main goal was to look for some small minnow mayflies.

I found none at the Lynch River -- not one.   They were here in the winter (genus Baetis: see my entry for 3/16), and I know from sampling with StreamWatch that they're here in large numbers again in the fall (genus Acentrella), but there were none to be found yesterday.

So, what did I find?  At first, nothing special.  Lifting rocks, I saw lots of flatheaded mayflies -- mostly Epeorus in terms of the genus -- and lots of spiny crawlers (Ephemerella, and a couple Drunella).   But I fared better when I spread out a leaf pack, one of the few I could find (this stream was "scoured" by the flooding rains we had in this part of the county at the end of last month).  Tons of spiny crawlers, of course, but also some beautiful stoneflies -- especially the one at the top of the page.  That's a Perlodid stonefly, genus Diploperla, and with those black-tipped wing pads, it will be hatching real soon.  Here's another look at this beautiful creature.

I also found, in terms of stoneflies, two other types of Perlodid: Isoperla montana, (I think that's the species) the most common Perlodid we see, and Isoperla holochlora (on which, see my recent entries on the Rapidan River and Powells Creek).   But a neat thing happened when I set up my gear to take pictures.  Look what showed up to supervise what I was doing!

Ain't that a beauty!  Perlodid stonefly, Isoperla montana, but an "adult" that had recently hatched.  And I got some really nice photos since it was in no hurry to leave!

On to today and Ballinger Creek (Fluvanna County).  Here I did find a small minnow mayfly, but it was a small one, and my pictures are not very good.

I preserved it so I could check out the genus.  It appears to be Acentrella -- the same genus of small minnow mayfly that I found last week at Buck Mt. Creek.   How do we know?  Well, it has two tails, and it has normal gills (that eliminates Heterocloeon) -- which brings us to Baetis or Acentrella.  If "metathoracic wing pads" are present, it's Baetis; if they are not, it's Acentrella.  Have a look for yourself (obviously, a microscope photo).

I've pointed to the posterior edge of the metathorax, where the wing pad should be: nothing there.  So, in the winter I found nothing by "two tailer" Baetis small minnow mayflies: so far I've found Heterocloeon and Acentrella at Buck Mt. Creek, "three tailer" Baetis at Powells Creek, and Acentrella again in Ballinger Creek.    We'll keep an eye on this as the summer develops.

I found a number of interesting insects this morning, including a grayish colored Freeliving caddisfly larva, a number of small Perlid stoneflies,  and a Hydrophilidae (water scavenger beetle, order Coleoptera).  This is a strange looking critter that we don't get to see all that often (the head's pointing right).

But the find that pleased me the most was this beautiful flatheaded mayfly, genus Stenacron, that had just recently "molted" (hence the very light color).  When I first saw such a light colored mayfly, I e-mailed Rose Brown, excited that I had found an "albino".  She quickly corrected my error!  Beautiful -- the way the dark gills stand out against the very light-colored body.  It won't take long for the pigment to turn this mayfly it's normal brownish gray.

The Lynch River in springtime.

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