Friday, April 13, 2012

The Baetis tricaudatus Hatch is Well Underway in the Mountains

(Above: photo of a newly emerged B. tricaudatus small minnow mayfly sent in by one of our readers.)

My friend who lives in Sugar Hollow has been finding lots of Baetis tricaudatus small minnow mayflies, both nymphs and adults.  So, we decided to meet up today and check out a new trib that flows into the Moormans.  You'll recall that B. tricaudatus is a very intolerant small minnow mayfly (1.5) that is typically found in small mountain streams.

 While the dominant taxon was, as expected, the spiny crawler mayfly, there were quite a few B. tricaudatus nymphs: I found 4 having looked for about 20 minutes.  Two were fully mature with black wing pads, and two had very long wing pads and clearly did not have long to go.  Two of the defining characteristics of this particular species are easy to spot in the photos below: 1) the middle tail is less than 1/2 as long as the two lateral tails, and 2) there is a pale, sometimes interrupted, line that runs the length of the abdomen.

In this one,  a B. tricaudatus nymph comes face-to-face with a young, Isoperla holochlora Perlodid stonefly.

The most common stonefly I saw in this stream was the Perlodid, Diploperla duplicata: I saw at least 20-30.  But I did find two I. holochloras, and it's easy to see in these photos how I. holochlora and I. nr. holochlora differ.  Note how the large yellow spot on the head merges with the yellow line of the labrum -- not what we saw yesterday.

A couple of other nice finds.

1) This freeliving caddisfly larva which I think is R. carolina -- but I need to do some microscope work on this to be sure.

And, 2) a Limnephilid (Northern case-maker), genus Pycnopsyche,  which has moved on from its case made of leaves to one that's quite substantial.  I think this taxon is also starting to hatch since I'm starting to find empty cases.


Yet another beautiful stream in Sugar Hollow to which we'll surely return.  So many streams -- so little time.

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