This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominalterga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
On Sunday July 28th, I drove 2-3 hours each way (traffic got crazy) to spend about 3 hours fishing and sampling bugs in a favorite small stream on the east side of the Cascades, where a meadow in the middle of a hot burn from a few years ago has produced surprisingly large (meaning up to 10") and spectacularly colorful Westslope Cutthroat Trout. It could almost be called a spring creek, at least in the meadow reaches, although the same clear, stable, spring-fed water tumbles through a rocky forest for most of its length.
It is by far the smallest stream I routinely fish, and sometimes it's so narrow the grass overlaps the water from both sides and leaves nowhere to cast. With the combination of close quarters, tight spaces, clear water, and bright sun, it was a real challenge to sneak up on fish and present a fly without spooking them.
Every once in a while it opens up to a "large pool" like this one, which held the biggest fish of the day (about 8.5").
The larger fish I've caught previously were either hiding under the cut banks for the day or living in bigger water downstream. It's possible I've seen them up this high in the past because I fished it about a month earlier and they were up there spawning. I explored the forested reach below for just a little while and caught one still in spawning colors.
I was as interested in bug collecting on this trip as in the fish themselves, because I figured the altitude (around 5,000 feet) and spring-fed nature of the system might offer something new to find. It didn't disappoint. By far the most abundant large nymphs in my kicknet sample were Drunella coloradensis, and I collected my first adults of this species as well.
Among the dozens of nymphs of that species, I found a single specimen of a really unique-looking mayfly nymph that got me excited, the ultra-spiky Drunella spinifera:
I also collected my first adult of the extremely common caddisfly genus Rhyacophila.
And sweeping around the grass overhanging the stream turned up a few specimens of Dolichopodidae, or Longlegged Flies.
