BEIJING, March 14 (Xinhuanet) -- Deceased rocker Jim Croce sang a hit song with lyrics that warned not to tug on Superman's cape, spit in the wind or pull the mask off the Lone Ranger, unless you're looking for trouble. In the insect world, unless you're looking for trouble, you don't mess with wasps that have black spots on their faces.

    That's according to a new study that reveals paper wasps sport black spots to warn others of their grappling prowess. You might say they're the kung fu masters of the wasp world.

    "Competition can be really costly, so you get these signals to reduce competition," explained researcher Elizabeth Tibbetts, a behavioral ecologist at the University of Michigan at Ann Arbor.

    Tibbetts spent a lot of time looking at paper wasps (Polistes dominulus). "I noticed all these different facial patterns and wondered why," she recalled. "And then, as I pursued it, I discovered they were getting used as signals."

    The better fed and larger these wasps are, the more black spots they often have on their yellow faces. Tibbetts reasoned the more spots wasp faces had, the more other wasps might shy away.

    The researchers perched dead wasps on top of sugar cubes and painted their faces with specific patterns. They next saw if other wasps dared approach the cubes. "The dead wasps kind of served like scarecrows for the other wasps," Tibbetts explained.

    The researchers found wasps preferred challenging guards with fewer spots and veered off from those with more spots. Tibbetts and her colleague Rebecca Lindsay detailed their findings online March 12 in the journal Biology Letters.

    "It's like karate belts," Tibbetts said. "Someone with a black belt is better than someone with a yellow belt. ... It's a convention we have to signal fighting ability."

    (Agencies)