The key I am looking at distinguishes Cricotopus sylvestris and C. flavibasis from C. trifasciatus and C. tricinctus thus:

10. At least one tergite in addition to abd 1 all or nearly all yellow-white; abd 1, 4 and 7 typically yellow-white ... (11)

10. Tergites behind abd 1 in no case all yellow-white or yellow-white with a dark saddle ... (12)

11 distinguishes C. trifasciatus and C. tricinctus

12 distinguishes C. sylvestris and C. flavibasis

If there is a dark ring at the front or back of a segment, I might be applying the key wrong if that counts as not "all yellow-white or yellow-white with a dark saddle."

Edit: The paper notes in text elsewhere that C. sylvestris is "the dominant species living in Myriophyllum spicatum in the Hudson River Estuary" and "when tergite 4 is light resemblence to C. trifasciatus is strong."

This key seems to contradict comments on Photo #245295. It would be nice to know if either the key is bad or I'm misunderstanding it.

Since Dr. Epler previously made a tentative ID for this midge to Cricotopus sylvestris and it seems to matches the midges in Photo #245295, I'm wondering if it should be moved to species.

Dr. Epler has warned me that Boesel's key is unreliable in separating members of the species group and I don't know how confident a "probably" from him is. (This is all a matter of language use and not a matter of expertise. Some people use probably to mean 51+% and others use to mean almost certainly.)

That's what I was thinking and why I didn't just move it myself.

I added an image in attempt to make sense of the abdominal segments. I am basing this interpretation on images I just added here.