Friday, April 19, 2013
One down: the Free-living caddisfly larva was Rhyacophila ledra/fenestra
The Rhyacophilid I found yesterday at the Doyles River (Blufton Road in Doylesville) appears to be Rhyacophila ledra. R. ledra cannot be distinguished from R. fenestra, but for larvae found in the mountains, R. ledra seems to be the name that's commonly used.
R. ledra (fenestra) is described by Beaty in the following way:
(R. fenestra)/ledra -- larva 14 mm; anal proleg without apicolateral spur or basoventral hook; no ventral teeth on anal claw; segment 2 of maxillary palpi longer than segment 1; head patterned with dark muscle scars posteriorly and darkened anteriorly. He adds: Larvae of these two species are currently inseparable. Piedmont and Coastal plain records of R. ledra may be R. fenestra as R. ledra in NC appears to be a Mountain species while R. fenestra is primarily a Piedmont species. (Steven Beaty, "The Trichoptera of North Carolina," p. 60)
Segment 2 of the maxillary palpi is indeed longer than segment 1 -- but I was unable to get a good photo of that. As for the absence of ventral teeth on the anal claws -- easy to see in this microscope photo.
The dark muscle scars on the back of the head -- and on the pronotum -- as well as the change in color from front to back is clear from all of our photos, but here is a close-up.
I have drawn attention to the inward curve of the anterior row of muscle scars on the pronotum because that curve can also be seen in the illustration of R. fenestra (ledra) in the article by Prather and Morse, "Eastern Nearctic Rhyacophila Species, with Revision of the Rhyacophila invaria Group," p. 160, illustration 73A. So we can add a new species of Rhyacophilid to our growing list of EPT taxa found in central Virginia.
One other point of interest. This is the third free-living caddisfly species that I have found in this one set of riffles in Doylesville.
The other two species are R. fuscula...
and R. carolina.
On the unknown Isoperla that I found yesterday -- I have a provisional ID of Isoperla orata, but that larva has been sent to Steven Beaty for further study. More on that once I hear back from him.