A nymph of the same species as this one emerged into a dun in my studio
so I got photos of both stages.
NOTE: I missed an important key characteristic the first time I tried to identify this one (robust setae
on the abdominal sternites
, which were harder to see than I expected but are clearly present), so I went on a bit of a wild goose chase and landed at a dead end. After spotting that characteristic, this one keys more straightforwardly to either Baetis tricaudatus
or the Baetis
piscatoris complex. It doesn't seem to be a perfect fit for either one in the key, but I'm going with tricaudatus
based on range and abundance. It's not certain.
However, I'm leaving the flawed analysis below with this disclaimer, because some aspects of how I approached that dead end might be informative in the future.
----Incorrect analysis below----
After spending a lot of time with this one under my shiny new microscope, I'm still not quite sure what it is. I botched my attempt to expose the mouth parts that might make the ID more definitive. Based on the key in Webb et al 2018's "Baetis
Larvae of North America," here's my reasoning at each key couplet.
Couplet 1. The pronotum
lacks dark, submedian U-shaped markings. Also, if I were to follow through to couplet 2, there seem to be characteristics that rule out each of the options: the intercalaris
complex is ruled out by the abdominal
markings, and the caudal filaments
have neither a dark median
band (ruling out the flavistriga
complex) nor uniform pale coloration (ruling out Baetis
notos). This sends me with decent confidence to couplet 4.
Couplet 4. I cannot find robust setae
in my microscope on the scapes
, or sterna
. I also do not see a pair of dark, bilobed
markings on the pronotum
. Unless I overlooked these characteristics, proceed to couplet 9.
Couplet 9. Abdominal tergum
5 is a bit paler than adjacent terga
, but "distinctly paler"? The figure for Baetis
alius in the paper, as well as a very nice picture posted by Millcreek
in the forum here, shows that Baetis
alius would have darker tergites
surrounding #5. So proceed to couplet 11.
Couplet 11. The length of the gills is obviously less than 2X their width. This leads to the Baetis
vernus complex, which could include that species or Baetis brunneicolor
. This key doesn't say how to tell those species apart.
Switching over to Burien et al 2018 as the source, the characteristics used to distinguish vernus from brunneicolor seem to rule out either one. Brunneicolor should have more uniformly brown abdominal tergites
, whereas vernus should have a lack of visible tracheation in most of the gills.
The fore femur
length is about 3.8x its width.
Also worth noting: In the genus ID, I thought I could see the villipore in my microscope, but I'm not sure. If I back out of Baetis
altogether and assume there's no villipore, I end up at Fallceon
, but this specimen doesn't seem to have the frontal keel on the head that's supposed to be present on Fallceon
quilleri. So that seems like a dead end as well.