Saturday, November 23, 2013

The Uenoid caddisfly season begins: "Little northern casemakers" at Lickinghole Creek

With the forecast for Sunday through Wednesday not looking real good, I decided to get out today before the nasty weather moves in.  Where to go?  Well, I hadn't been to Lickinghole Creek in Crozet for a very long time, and it's a good stream to look for Uenoids, so I thought I'd give it a try.
And hooray, hooray, I found a Uenoid -- the first of the season!   It was a very small larva -- 5 mm -- but it still made a very colorful case.

I thought it would probably be the common species Neophylax oligius, but when I looked at my photos I was uncertain about that ID.  Take a close look at the head.

According to Beaty -- "The Trichoptera of North Carolina," p. 87 -- N. oligius has a "yellow stripe on [its] head" which "should be greater than 1/2 [the] head length."  I.e. it should look like this.

That's not quite what we have.  So, what about Neophylax consimilis which has a "stripe or pale area which is less than 1/2 [the] head length"?  (Beaty, p. 86)  N. consimilis looks like this.

Here was my quandry -- was the larva I found N. consimilis, or was it a "young" N. oligius on which the stripe on the head was not fully developed?  Toughy, especially since Beaty notes that the head "stripes" on these two species often blend into one another.

In the end, I had to look at the underside of the head.  On N. consimilis the underside of the head is "usually dark" (Beaty, p. 87); on N. oligius it's usually "testaceous" (brownish red or brownish yellow).  Here's how they differ.

N. consimilis:

N. oligius:

Which do we have?  I'd say it's N. oligius with a stripe that's not yet as long as it's going to be.

Here's a microscope view of the underside of the head on which you can also see the "clavate, ventral gills"  (they're found on both of our species.)

Sorry.  That's a long way to go to establish a species ID, but I like to figure them out when I can.

Other photos today...lots of small winter stoneflies.

1. Small winter stonefly, Allocapnia pygmaea.

2. Small winter stonefly, Allocapnia mystica.  (Note the different shape of the pronotum and the "burnt orange" abdomen.)

3. And of course, there was at least one Clioperla clio Perlodid hanging around.


Welcome back to the Uenoids!

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