Over generations, fly fishers have created artificial flies that look nothing like natural insects, but catch fish when nothing else will. Attractor flies such as the Royal Coachman and the Humpy may work precisely because they do look different. When a big, buggy-looking thing comes floating along, it often will provoke an opportunistic predator to strike.
Baitfish Fish eat other fish, including their own offspring.
Some fly fishers believe that trout prefer streamers that look like their own kind. Most fly tiers create streamer patterns to simulate minnows, but some famous flies, such as the Mickey Finn, a freshwater fly, and Lefty's Deceiver, a saltwater pattern, catch many fish even though, to the human eye, they resemble nothing in nature. That may be the key to their success. Predators strike prey that appears to be escaping, crippled, or so abundant that it will be easy to get without expending much energy. When a predatory fish attacks a school of bait, the attacker looks for prey that appear to be different from the others.