The IOBO floats like a cork when freshly tied. It is highly visible which makes it particularly attractive to the angler. Of course, some colors are more visible under certain conditions then others. I prefer Medium Dun as an all around favorite.
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| IOBO floating as seen from above. | IOBO floating as see from below. |
For those of you who believe that color is important for dry flys (I don't), pick a feather color approximating the natural. Tie it onto a 5X tippet and put the fly on the water. Preferably, do some form of "pile" cast leaving slack in the leader for a drag free drift. You can cast up-stream, down stream, across stream or quartering up or down.
Most times the takes are very confident and not splashy; you'll have plenty of time to set the hook and one of the biggest mistakes is to try and set the hook too quickly. The exception seems to be sometimes during caddis hatches when the take can at times be sudden and hard.
One deadly technique is to quarter a cast downstream with an IOBO that is partially wetted (perhaps cast 40 or 50 times). As the slack comes out of the leader you'll find that you can lift the rod tip which will cause the IOBO to be pulled beneath the surface. Dropping the rod tip creates slack again and the IOBO pops to the surface imitating an emerger. If you use this same technique on a fresh IOBO it will skitter as a dry and is also deadly; you can even shake out extra line to extend the drift.
While it's dry, letting the IOBO drag, causing it to skitter on the surface can also be effective; particularly with the IOBO Humpy in a Caddis hatch.
Although I hate to admit it, it will also catch fish submerged on the swing.