London, Aug 20 (IANS) You need to look a wasp in the face to tell whether it is angry before it stings you, say scientists. But be warned. If you dare undertake such a venture, it might leave you with painful consequences.

Wasps showcase aggressiveness by the markings on their heads. The more black spots, the more ferocious it is, reports the Daily Mail.

Elizabeth Tibbetts of the University of Michigan, US, set out to find why paper wasps have highly patterned faces.

To test her theory that plenty of black spots were a sign of a violent personality, she perched dead wasps on top of sugar cubes and painted their faces with specific patterns.

She then observed that other wasps were less likely to approach the wasps with the most painted faces.

‘It’s the animal version of the karate belt. Someone with a black belt is better than someone with a yellow belt. It’s a convention that we have to signal fighting ability,’ Tibbetts said.

In another experiment, published in the journal Current Biology, she looked at how live wasps reacted to one another’s spots.

A group of less aggressive wasps was given ferocious spots while a similar group was given a hormone that made them aggressive. A third group was treated to spots and the hormone.

The insects that failed to live up to their spotted faces provoked other wasps the most in fights, suggesting they objected to being conned.

All the paper wasps, common across Europe but rarer in Britain, that Tibbetts looked at were queens who fight with bite and box while trying to establish who rules a nest.

Wasps become a particular problem at the end of summer season, when their growing numbers leave them short of food — making human food and drink all the more appealing.

Only the female wasp stings by injecting her load of venom in a third of a second. As she stings, she releases a chemical message that invites all wasps in the area to join in the attack.