Monday, November 20, 2017

The "Strong Casemaker," Psilotreta rufa: It's a new species for me

It's not all that often that I find what I'm after, but I lucked out this morning.  This is a caddisfly that my friend found a number of years ago in the pristine stream that flows by her home, but this is the first time I've seen it.  Odontoceridae (Strong Casemaker), Psilotreta rufa.

Location?  Same stream as before.

But it didn't look like that today.  Today, the flow was reduced to a trickle.  The drought we've had here this fall has really taken a toll on these small streams in Sugar Hollow.  We were lucky to find anything in there at all.

Let's establish the species ID using Beaty ("The Trichoptera of North Carolina," p. 97)

(P. rufa) -- larvae up to 11 mm; head and pronotum uniformly reddish brown without stripes but may have darker pigmentation along frontoclypeal and coronal sutures...head longer than wide and relatively flat between carinae; seta 17 about half the length of seta 15; pronotum darker laterally; anterolateral pronotal projections short.

1) Our larva was 10 mm.

2) Yes, on the color of the head and pronotum -- "uniformly reddish brown" -- and yes, dark stripes are missing.

3) It's hard to see the frontoclypeal and coronal sutures in any of the photos I've taken.  Still, you can easily see that the entire top of the head -- the frontoclypeus -- is darker than the sides.

4) Yes, the head is longer than wide, and it's relatively flat between the carinae.  For the carinae, let me use a photo my friend took some time ago.

5) The lengths of setae 17 and 15 are critical to the ID, and I was able to get a decent microscope photo showing them both.

For sure, seta 17 is about half the length of seta 15. 

6)  I can't say that the pronotum on this larva looks darker laterally than the rest (except for tips of the projections), but the pronotal projections are definitely short.

Psilotreta rufa.


This is the third species of Psilotreta that I've found in our streams.  On the other two, by the way, there are black stripes on the head and the pronotum.

Psilotra labida

and Psilotreta frontalis

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