Aggressive mimicry
<p>In the natural world, numerous species use mimicry — counterfeiting the appearance of another species or object — to hide from or deter predators. A smaller number are themselves predators, and use mimicry not for defense, but as a way to get closer to their prey. One of the most remarkable of these aggressive mimics is a small fish called the sabre-toothed blenny, which mimics another fish, the bluestreak cleaner wrasse. The wrasse enjoys a mutualist relationship with some larger fishes: it 'cleans' the bigger fish by eating parasites and dead tissue, something that benefits both parties. The big fish recognize the wrasse by its appearance, and by the 'dance' that it performs as it approaches.</p>
<p>The blenny closely resembles the wrasse and even duplicates the wrasse's distinctive dance. The fish that mistakes a blenny for a wrasse is in for a nasty surprise, however. Instead of virtuously cleaning up its unwary victim, the blenny will simply bite off a chunk of flesh and then take off at high speed.</p>
http://www.spamnation.info/blog/archives/2010/02/spam-scams-and-aggressive-mimicry.html