Birds do it, and so do goldfish in the privacy of their bowls, but no one thought that insects did it the same way--recognize each other on sight, that is. Now a study reveals that wasps may not be faceless ciphers to one another after all.
Birds, mammals, fishes, and reptiles can recognize specific individuals, a trait essential to monogamy and other vital relationships. Although many social insects use chemical cues to decide whether someone belongs in their nest, many scientists doubted that insects had the brainpower to recognize individuals. But the wildly variable patterns of yellow and black blotches and stripes on the faces and abdomens of paper wasps (Polistes fuscatus) led behavioral ecologist Elizabeth Tibbetts of Cornell University to wonder if wasps use these marks to sort out their unique places in their pecking orders--strict hierarchies where wasps are ordered like rungs on a ladder.
To test her notion, Tibbetts decided to do a little face painting. She gathered worker and queen wasps from 23 nests, then chose one wasp from each nest for a makeover. With a very small brush, Tibbetts painted half the faces with a wasplike pattern of tiny black and yellow stripes. She did a "sham" paint job on the rest, painting over their natural patterns without altering them. When the wasps were returned to their nests, those with the altered markings were attacked more often than wasps whose paint jobs coincided with their original patterns--even though they retained the chemical cues that they belonged in the nest, Tibbetts reports in the 22 July issue of the Proceedings of the Royal Society. The attacks stopped after about 2 hours, however, indicating that the wasps had regained their places in the hierarchy. The relatively minor drubbing the made-over wasps received (compared to the mauling dealt wasps from other nests) suggests to Tibbetts that the other wasps recognized them as nest mates, but knew they didn't look right for the job.
Animal behaviorist George Gamboa of Oakland University in Rochester, Michigan, says the results are "surprising because most of us who work with social insects assume that the communication in a colony is largely chemical." Gamboa says a more compelling demonstration would be to show that a low-ranking wasp painted to look like a queen commanded queenlike treatment from its nest mates. Tibbetts isn't sure she can muster the artistic skill for that experiment, though: "It's one thing to paint a wasp to look unfamiliar, but quite another to paint a wasp so it looks like another wasp," she quips.