Muddler Minnow originated by Don Gapen (USA) in 1937 to imitate baitfish (sculpins) in his local rivers. The colors on the fly, and the broad head is a good imitation of an Alpine Bullhead (Cottus poecilopus) found throughout Europe. Even though it's a streamer, meant to look like a fish, The Muddler Minnow have proven to be a good fly when grasshoppers and big caddis are on the diet too, to mention some..
Muddler Minnow is a fly for an active retrieve and works best in foul weather in the lakes. In rivers you can fish it with the traditional "swing" and retrieve. The broad head on the fly moves a lot of water that makes it easier for the fish to register it in the water.