Thursday, April 23, 2015

Identified at last! Well, sort of... One of our unknown Isoperlas

A torrential rainfall on Tuesday night has left almost all of our streams high, fast, and off-color.  So, I went to one of the smallest streams in Sugar Hollow that I could explore.  And I found one of the insects I was hoping to find.

This is a Perlodid stonefly, genus Isoperla, species unknown.   I've found it every year in the spring in at least three headwater streams in this valley.   Always in April and May.  This was the first -- discovered on 5/18/11.

I sent this nymph to Steven Beaty: he said it was one that he hadn't seen.   To his knowledge it had not yet been associated with an adult.  However, in a recent communication, he acknowledged that this nymph is now recognized from other parts of Virginia -- in the Blue Ridge -- and for the moment he's calling it "Isoperla sp. VA".  (Curiously, Beaty notes "collected only from SW Virginia along Skyline Drive and on WV and VA border. ???)   So, some progress.  It remains to have someone "rear" one of these  nymph and provide us with a name.  Not sure if that's on Beaty's agenda this year or not.

The distinguishing features are 1) the pale brown body color, and 2) the pattern we find on the head...which is this.

Those features might be easier seen on this nymph, found on 5/2/12.

One caveat -- it might look quite different when it's fully mature.  The following nymph was also found on 5/18/11.   The body color's exactly the same, but the head pattern is quite different.

In any event, the nymph that I found today was still very small.  I'll have to come back in May -- maybe late May this year -- to pick up nymphs that are closer to being mature.


While I found a lot of insects today -- still lots of E. pleuralis flatheaded mayflies around -- I only photographed one other thing: the Ameletid mayfly, Ameletus cryptostimulus.

Very pretty.  And you know you're in a good stream when you find this particular species.

Tomorrow, off to the Rapidan River which I hope has dropped a little by now.

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