*Is nonselective the right word? It seems like there should be a better word to describe a fish that tends to eat any decent looking fly that drifts its way, but I can't think of what it is. Even thesaurus.com didn't help out with any good antonyms of selective.
With other aquatic insects--mayflies, caddis, and the like--it seems as though you can get sometimes catch a real picky trout with a good presentation and a general pattern. I've watched good fisherman take what I thought were quite discerning fish using an Elk Hair Caddis or a Humpy by putting the fly in just the right spot in just the right way. Because I feel like I need all the help I can get, I don't usually try those types of flies in tough spots. I try the Thorax PMD, or the Sparkle Wing Trico, or whatever fly I think might work in spite of my own mediocre presentation.
With that being said, I think there are some fish that even those priests* of presentation can only catch using just the right pattern--or more accurately one of the right patterns (there are always more than one). And one way to identify such fish, or perhaps rivers that house such fish, is to fish a midge hatch.
*I say priests because there is a contingent of anglers who very much like to ramble on about the church of presentation over pattern. They are somewhat religious in their beliefs that the perfect presentation can overcome anything. That, however, is probably a separate post.
For some reason, and maybe its just me, but the midge hatch seems to bring up the pickiest eaters. Or else trout are simply pickiest about midges. Maybe your average trout says to himself (or herself): if I am going to be forced to eat such tiny fare, it better dang well look just the way I prefer. Okay, so I don't know what they say, but it seems to be true that they get quite selective. At least in my own anecdotal, biased experience. Especially in tailwaters were each square foot of riverbed is carpeted with a hundred thousand midge larva.
Now, I grew up as a fly fisherman thinking the Griffith's Gnat was the end-all, be-all of trout flies. For several years, I held the opinion that there was no fish alive that could resist its iridescent charms. The day I discovered trout that turned their noses to the Griffith's Gnat was essentially the day I lost my childhood innocence as a fly fisherman. It was the day I ceased to be a happy, naive fisher boy and morphed into a jaded, angst-ridden fisher man. A part of my fishing heart still loves the Griffith's for what it represents in my past--a secret weapon.
But the truth is that the Griffith's really represents a midge cluster. And sometimes, picky trout especially, get hooked on individual midges--be it emergers or adults. I discovered Tak's Biot Wing Adult in the book Modern Midges, which could have been titled The Modern Encyclopedia of Midge Patterns. Its got over a 1,000 midge patterns in its pages, though it should be noted that a vast number differ only in color from the midge next to them on the page.
My limited experience with Tak's midge (originated by Rick Takahashi, who is credited as one of the authors of Modern Midges) is that it will take midging fish that will generally refuse a Griffith's Gnat. Beyond that, its got the other major attributes I look for in a fly: its quick and easy to tie. I mean, if I have to tie a size 22, it better be an easy pattern. And this fly, after you tie a couple, is relatively simple. Though perhaps not simple enough for my world-class laziness. You'll note that I have left the ribbing off of my version.
Anyway, this is one I plan to use quite a bit this year. Especially in the coming months when the midge hatches serve as the dry fly fix for topwater junkies who are caught between a winter of nothingness (or nymphing) and the promise of the oh-so-fantastic blue-winged olives.