This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.
A cult following is something to which few insects can lay claim, but the tiny Tricorythodes mayflies certainly qualify. Their widespread, reliable, heavy hatches draw impressive rises of ultra-selective trout which demand the most of a technical dry-fly angler's skills.
It is surprising that such a great hatch took so long to come to the attention of fly fishermen. The Tricos were first introduced to anglers in a 1969 Outdoor Life article by Vincent Marinaro, who misidentified them as Caenis. By the early 1970s the identification had been corrected but Swisher and Richards still wrote in Selective Trout, "Few anglers are familiar with these extremely small but important mayflies." The next wave of publications boosted Tricorythodes to its current fame. I suspect their early dismissal was due in part to tackle limitations; anglers in the 1950s had no means to effectively tie and present size 22-28 flies.
In their winged lifestages, Baetis mayflies have (2) tails, whereas Caenis and Tricorythodes mayflies have (3) tails.
Caenis and Tricorythodes mayflies, which have only forewings, can be differentiated based on forewing venation, whereas Baetis mayflies generally have greatly reduced hind wings, or for a few species, are completely absent hind wings.
Hope this helps, but if this just leads to more questions, I would be happy to answer them.
Martinlf on Jul 9, 2018July 9th, 2018, 9:39 am EDT
The Trico hatch for most of here in the East, leads to fishing spinners, which typically fall when the cooler morning air reaches about 70 degrees. This spinnerfall is often an early to late morning event. Those who fish the Trico duns typically fish a female pattern, as the males hatch at night, and the females hatch around sunrise, or earlier, until fall when one may find them coming off mid to late morning in the cooler weather. Spring Baetis, the most fished hatch where I live, typically come off a bit later in the day, between 10 a.m. and 3:00 p.m., though this is not the only time they can hatch. These are duns. I believe both males and females hatch roughly at the same time, unlike Tricos. Fishing the spring Baetis here rarely focuses on spinners, at least in my experience. I don't know much about Caenis.
"He spread them a yard and a half. 'And every one that got away is this big.'"