Do insects know each other's faces? (Wasp Painting).

A researcher who dabbed tiny stripes on the faces and abdomens of paper wasps says that she's found the first evidence that the insects can recognize individuals by their markings.

A paper wasp given a fancy paint job and returned to her colony met who-the-heck-are-you aggression, says Elizabeth Tibbetts of Cornell University. Wasps naturally show lots of variety in yellow, black, and brown patterns, which could provide visual cues to their identity, she reports in an upcoming issue of Proceedings of the Royal Society of London B.

A longtime investigator ot kin recognition in wasps, George Gamboa of Oakland University in Rochester, Mich., welcomes insect painting as a novel approach to an old question. Plenty of experiments have shown that wasps and other social insects can tell a nest mate from an outsider, but it's been much harder to show recognition of individuals. Tibbetts' evidence is "highly suggestive" of it, says Gamboa.

Because the wasps, Polistes fuscatus, maintain a pecking order, observers have long speculated that colony members can tell who's who. At a nest's founding, fights are furious but eventually taper off into ritualized encounters. "Subordinates often move out of the way or lower their antennae when dominants approach," says Tibbetts.

In exploring the possibility of visual cues in such encounters, she surveyed 38 wasp nests around Ithaca, N.Y. She found 48 variations in stripe positions alone, never mind stripe thickness or patterns of the wasps' brown blotches. There was no apparent correlation between the markings and wasp health or social rank.

At several dozen nests, Tibbetts removed a chilly, sluggish wasp between 5 a.m. and 7 a.m. Wearing plastic dishwashing gloves, she used a toothpick whittled down to a fine point to add tiny stripes of yellow or to black out some of the wasp's natural stripes. "It took me a while to get the technique worked out," Tibbetts says.

For comparison, she painted the same wasp on another day with little dabs of black paint on black areas so the overall look didn't change. Tibbetts tested dominant wasps, as well as lower-ranking workers, and she altered both facial and abdominal stripes.

None of the painted wasps got chased from the nest when Tibbetts returned them. She speculates that their basic odor still identified them as belonging to the colony. However, Tibbetts reports that returnees with altered patterns ran into roughly twice the number of aggressive gestures--predominately mild ones such as lunges and darts--as did wasps with paint that did not alter their basic markings.

Aggression dwindled during the day after the return, and Tibbetts suggests that each colony worked out the rank of the painted wasp and settled back into its routine.

Peter Nonacs of the University of California, Los Angeles says he'd like to see a more detailed analysis of the aggressive reactions that takes into account the insects' activities. "This objection aside," he says, "Tibbetts' work does strongly suggest individual recognition" among the wasps.

To settle the question of visual cues to identity, Gamboa suggests that Tibbetts disguise a lowly worker wasp by painting her to match her queen. Tibbetts laughs, saying that her wasp-painting skills would have to improve.