Tuesday, March 15, 2011

The Doyles River: Watching Things Grow and Mature

First of all, it was not a good day for photos, so I'm not thrilled with the shots I'm including today.  It was cloudy and dark -- not good conditions for macro photography.  That being said, it was a good day to take note of how the mayflies are maturing, and for noting the changes in color and shape that occur as they do.

The photo above is of a fairly mature spiny crawler (family: Ephemerellidae; genus Ephemerella).  This is the common genus we see in our streams in the spring, and the colors and patterns are what I'd call "normal" -- olive green/brown, and highly patterned.  This is a live shot.  When I got home and looked in my vial to see what I had preserved, I discovered that I had two other, much smaller, spiny crawlers  -- and note how they differ in color.

The smallest (bottom left) is quite light in color and not highly patterned: to its right is one that's a bit bigger; it's colors are darker and it's quite richly patterned.  And finally, the large nymph at the top is the same nymph that is in the live shot at the top of the page.  And if we want even greater contrast, let's look again at the tiny, tiny spiny (here highly magnified -- 45X) that I found in this very same spot almost one month ago (2/14).

Very pale, with just the barest amount of "mottling" on the thorax and head.

Another example of how things change in color in shape as they mature -- a couple of small minnow mayflies.  Here's a photo of a small minnow (genus Baetis) I found at this spot in the Doyles (near White Hall, VA) on February 14.

Light green/yellow/brown, and you can see the primary wingpads -- but they're not very long.  Today I was finding VERY big small minnow mayflies that looked almost black.  For example:

(If you can't see the tips of the wingpads, click on the photo to enlarge it.)  At first I thought I had found some other genus -- but no, they're genus Baetis, it's just that they're fully mature, with black wingpads, and they're ready to hatch any day.  Here's a microscope photo of that same insect next to a younger Baetis that I also brought home today.  On this shot, the large wingpads stand out very clearly.

The other interesting find I made today was examples of three different Perlodid stonefly genera (Clioperla, Diploperla, and Isoperla) -- all in the stream at the same time, and all in different stages of growth.  The Clioperla Perlodids were very large, and I didn't keep any or photograph them since I've done so often before.  If the reader forgets what they look like -- here's a picture I took of Clioperla at Buck Mt. Creek almost one month ago.

The Clioperlas I saw today were about the same size.  The Diploperla Perlodids I found were approaching maturity, but the wingpads were not yet fully developed (they don't flare out to the sides at the bottom).  Here is a live shot I took.

Compare this in size -- and color -- to the much larger nymph that I found at a branch of the Moormans on 3/3:

The Isoperla Perlodids I found were not identified at the stream -- they were too small.  For that I needed my microscope.  In the photo below, the two nymphs on the right are Isoperla; the larger nymph on the left is Diploperla.  Not a great picture -- but it makes the point of how small they were.  We find a lot of Isoperla Perlodids in May: then they'll be fully mature.

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