Social insects such as wasps, bees, and ants rely on sight and odor to distinguish a nest mate from an outsider, but can they decipher between individuals? Elizabeth Tibbetts claims to have discovered the first evidence that some insects can recognize individuals. Her subject was Polistes fuscatus, a species of paper wasps known to maintain a pecking order, suggesting that colony members can tell one wasp from another.
Due to the rich variety of coloring and markings on the bodies of the wasps, she guessed that they use visual clues to tell one individual from another. But after studying the variations in color and marking patterns, such as stripe positions and stripe thickness, she could find no apparent correlations between the wasps' markings and their health or social rank.
Therefore, she began removing wasps from their nests and painting them. She deliberately altered the appearance of some of the wasps by adding tiny stripes where there were none, or by blacking out their natural stripes. To others, she tried not to alter their markings, but instead put a dab of black paint on what was already black.
When she returned the wasps to their nests, the ones with new stripes or now missing stripes were met with twice the number of aggressive gestures than did the wasps with paint that did not alter their natural markings. Within several hours, though, aggression tapered off, suggesting that the colonies had worked out their ranks and gotten back into their routines. Though this research isn't entirely conclusive as to whether insects can recognize individuality by visual clues, it is indeed suggestive.