Up to 10cms in diameter, the Mauve Stinger as it has recently become known or Pelagia noctiluca is extremely beautiful but has an excruciating sting. My daughter still has a scar on her leg from a sting over 20 years ago. It appears off northern and western coasts of Britain in summer most years. In the Mediterranean, it has become very common and huge swarms of them have resulted in the closure of many popular beaches in the last few years. Colour varies from purple to a reddish brown and is usually spotted. It is strongly phosphorescent when disturbed at night.