These duns were emerging sporadically throughout a cloudy evening at the end of June. Had I looked more closely when I caught this one and realized it represented my first collection of this genus, or just noticed the really striking coloration, I would have set my fly rod on shore and spent more time lurking mid-river with my net trying to catch more of them emerging (and at least one in better shape).
It's always a bit difficult to identify a female dun, but in this case the three longitudinal
stripes on the sternites
are very distinctive and narrow the choices to Caudatella heterocaudata
and Caudatella columbiella
. However, the length of the fore wing measured with a caliper is 7.25 mm, whereas columbiella
should be no more than 6 mm, so heterocaudata
appears to be the correct ID.