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Photo#876471
Isoperla marmorata - voucher specimen, in alcohol - Isoperla marmorata

Isoperla marmorata - voucher specimen, in alcohol - Isoperla marmorata
Healdsburg, Russian River, Sonoma County, California, USA
January 29, 2013
Size: 14 mm
Identified using John B. Sandberg's article in Illiesia: "The Isoperla of California (Plecoptera: Perlodidae); larval descriptions and a key to 17 western Nearctic species" 2011. The size noted above refers to body length and excludes the cerci which add another 7 mm to the length.

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Isoperla marmorata - voucher specimen, in alcohol - Isoperla marmorata Isoperla marmorata - voucher specimen, in alcohol - Isoperla marmorata Isoperla marmorata - voucher specimen, in alcohol - Isoperla marmorata

Probably Correct & Nice Work!
Mark, the key you cited guides users through several other larval characters not documented in your uploaded series. Please try to take additional photographs of the mouthpart called the Lacinia (hand-shaped part of the Maxilla). You will need dissect it from the ventral head and mount it on a microscope slide with coverslip for best results. You must zoom in very close (100x, either by camera or by use of compound microscope). This will eliminate many of the other California species in the key. I only suggest this because the use of only pigment pattern in any determination is flawed by natural variations amongst and between species, and habitats. And lastly, although your series is most likely a mature Isoperla larva, the cited key is restricted to only males so a nice 50x photo of abdominal sterna 8-9 focusing upon the posterior margins would suffice. Keep up the good work (very nice photos) and as a good rule of thumb, try to photo-document as many of the diagnostic key characters as you can to support your determinations for any species identification. Cheers!

 
Isoperla marmorata
John, Thanks for the info. I did dissect out the mouthparts before attempting to identify the nymphs to species and they matched. However I'm not sure I'm a good enough photographer to get the resolution required. Good point about pigment patterns not being too reliable, I have several series of photos of Plecoptera species which I'll be posting in the next few days and some of these show considerable variation within the species.

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