Sunday, July 7, 2013

Make that "four" common netspinner species at the Moormans on the Fourth of July: Hydropsyche rossi

I've been reviewing my photos from July the 4th, and I've noticed that I actually found four netspinner species at the Moormans that day, not three as I had posted.   In one small stretch of that stream, I found Ceratopsyche sparna, Ceratopsyche bronta, Hydropsyche betteni, and Hydropsyche rossi.  Pretty impressive.

I had failed to notice the anterolateral spots on that larva in the photo at the top of the page.  These:

The head pattern of H. rossi larvae is similar to that of H. venularis, which is described by Schuster and Etnier in the following way: "Head bronze in color.  Frontoclypeus with two pairs of yellow spots anterolaterally; anterior spots larger than posterior spots.  Spots often fused to form two, large, anterolateral spots."  (Schuster and Etnier, p. 96) Note that they are fused on our larva.  For reference -- here is a photo taken last year of H. venularis.

But H. rossi and H. venularis can be distinguished in the following way: H. rossi -- "rows of muscle scars on side of head not curved dorsad posteriorly"; H. venularis -- "muscle scars on side of head in rows that curve dorsad posteriorly."  (Beaty, "The Trichoptera of North Carolina," p. 76)

Here's a look at those curved muscle scars on H. venularis -- they move up towards the top of the head.

But here are the muscle scars on our larva from the Moormans:

Hydropsyche rossi.  Tolerance value, 4.8.  Not sure how I missed that one on Thursday.

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