Sunday, March 27, 2011

Mayflies: Pictures of How they Change, Pt. II.

The small minnow mayfly nymph eventually looks like this: the "Blue-winged Olive," a favorite of fly fishermen both in the spring and the fall.

This is a continuation of the previous entry, and what I said there holds true here as well: the small minnow nymph becomes darker as it grows and matures, the patterns on it are richer, and the wingpads become longer.   And although they start out almost transparent, they turn black as the nymph gets ready to hatch.

In my introduction to "The small minnow mayfly," (1/2/11), I noted that I've seen, to date, three different genera of this nymph in our streams: Baetis, Heterocloeon, and Acentrella.  All of the small minnows I've seen this winter have been genus Baetis -- the "two-tailers" not the "three-tailers".  And here are some of the pictures I've taken, documenting the changes that they go through.  Unfortunately, my documentation is not as complete here as it was for the Epeorus genus of the flatheaded mayfly and does not cover as long a period of time.  I'm quite sure I missed the earliest stages, when the nymphs first emerged from the substrate.

1. 2/14/11: Doyles River.  Note that the wingpads hardly reach to the second abdominal segment.

2. 3/1/11: Buck Mt. Creek.  Wingpads are longer, but still transparent (please click on the picture to enlarge the image.)

3. 3/15/11: Lynch River.  The wingpads are black -- probably meaning this insect is close to hatching.
The wingpads reach to the third abdominal segment.

4.  3/15/11: Lynch River.  A totally black small minnow.  I suspect that this is a different species than the one pictured above -- but such a determination is beyond my level of expertise.  Still -- a beautiful nymph!

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