Try Wing Vein Coloration to Separate Argia agrioides and A. nahuana
I recently took a trip to south-central Oregon to photograph Argia nahuana
(Aztec Dancer) and I was struck by something when I reviewed my photos later
on. Some of the major veins were distinctly paler (light brown or golden)
than the others and these were quite obvious in good, well-exposed photos.
Argia agrioides (California Dancer) was present on the same stream with
nahuana, so I did photograph them as well. Their veins were more uniformly
dark in my photos.
I went through my specimens after returning home, and I found the same
difference among them, with some variation (particularly with nahuana). I
also talked to Ken Tennessen, Tim Manolis, and Rosser Garrison who examined
their own specimens, and they found the same thing.
The conclusion I came to is that if the subcosta, radial anterior (RA),
radial posterior first branch (RP1), and cubitus were contrastingly paler
than the other veins (especially the costa proximal to the nodus, and the
veins posterior to RP1), then nahuana is the safe assumption; uniformly dark
veins could indicate either species given the variation in nahuana and other
factors, particularly when dealing with photos (angle, lighting, camera
exposure settings, whether flash was used or not, image processing).
I have put together a web page discussing this character and illustrating it
with several photos of both species:
may help you target individuals of nahuana where they are not known to occur
within the range of agrioides, and vice versa, but I'd say that any
individuals of either species found outside of their known range need to be
Since I live several hours from the nearest locations of either species, I
haven't had a chance to test this difference in the field (e.g. through
binoculars), but I encourage others to look for it. I'd be interested in
hearing about your experiences with it.
[Non-text portions of this message have been removed]