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.