Fly fishing writer A.J. McClane, in his famous book "The Practical Fly Fisherman" , writes in depth about spider flies. In it he sings their praises & says that they can be used to catch trout just about anywhere & at most times of the year. Well, I think he's right. Spider flies will bring up big trout from the depths during summer like nothing else. They are best used in the flat, smooth water that flows near the stream bank. At this time of year look for such a spot with a tree overhanging & providing shade. The trout will be positioned just below the overhang sipping any terrestrial insects, like ants, that may fall into the water. By the way, this time of year, I'm always looking for a dead tree next to the water that's infested with bugs. They fall off the tree & into the water, becoming trout food. It's also a plus that the tree adds cover & shade for the trout.
So basically, use these spider dry flies where ever you would think of using a terrestrial pattern. The added bonus of using these larger flies is that they're a lot more visible than, say, a size #22 ant.
Casting these flies can be a bit difficult because of their size & wind resistance, but it's worth the effort. On windy days especially, the breeze may actually push your fly across the water & mess up your drift. Not to worry though, that can be a very good thing. Unlike other dry flies where you're trying to get a drift with no drag, as to imitate a drifting insect (that doesn't have a leader attached to it), these spider flies will cause strikes when they move in an unusual way. Maybe it looks like a struggling life form on the water that would make an easy meal? Even if you botch the cast & drag sets in instantly on your line, let it finish out it's drift through your target areas on the water. The strange movement of the fly could very well excite the trout to strike it. This is a very nice effect these spider flies seem to have. So even if your cast, or the drift, goes haywire don't stress it. All is not lost & a trout may still take the fly. Essentially any of us, at all skill levels, can use these flies successfully.
McClane notes that trout tend to take these flies in an unusual way. They rise to the fly violently & jump out of the water to a degree, then take the fly on their downward plunge back into the water. So, if you try to set the hook too soon, you'll miss the trout. However, I've found that when trout strike a fly this way, they practically hook themselves. You just have to hesitate for a second & fight your instinct to set the hook quickly.
These flies don't tend to do well on fast, riffled water. I think its because that type of water doesn't give the fish a good view of the fly, even with it's large profile. Either way, this effective fly will have you fishing the smoother water.
So, as you head out for some summer trout, be sure to tie up & bring along some of these dry flies. They could make for a really fun day & some great fishing action.