The sensory form that an act of mimicry takes varies according to the sensory talents of the mimic's target audience. Most familiar to us visual primates are the visual mimics, the ones adapted to fool the eye, like the riparian frogs that crouch in a riverbed and look as slick and round and inorganic as the polished stones around them, or the caterpillar that, when frightened, will hold up its front end to flash a fluorescent salmon pink face with a pair of scary snake eyes. But there are vocal mimics too, like a palatable species of tiger moth that deters bats by parodying the ultrasonic clicks of a toxic moth the bats detest, or like the greater racket-tailed drongo of Sri Lanka, which mimics the calls of other birds to drum up a mixed-species flock in which the drongos can more safely and efficiently forage.
Then there are olfactory mimics, such as that mad parfumier the bolas spider, which can lure male moths by secreting perfect knockoffs of the counterpart females' eaux de toilette. There are even tactile mimics, including a parasitic fungus that lives in the inner chambers of termite mounds, where it is kept warm, moist, and competitor free. Termites are notoriously zealous housekeepers. How does the fungus elicit indulgence rather than expulsion? By assuming the shape and texture of ripe termite eggs.
Mimicry fables can sound like O. Henry stories, offbeat dilemmas dapperly resolved. For example, caterpillars are voracious eaters. They chomp their way through many leaves in their lifetimes. Birds love fattened caterpillars, and as they fly overhead, they search for signs of caterpillar activity, most notably damaged leaves. To thwart the aerial reconnaissance, one species of caterpillar has adopted a novel dining style. Rather than tearing through foliage at random, the Geometridae caterpillar cuts its leaves deftly, mincingly, moving along the edges like a seamstress with her scissors, in and out, zig and zag. By the time the caterpillar is done, the leaves may be much smaller, but their borders maintain their maiden serrated form.
Sometimes the best offense is a ghoulish pretense. Reporting recently in the Proceedings of the National Academy of Sciences, Leslie Saul-Gershenz and Jocelyn Millar described the case of the abominable blister beetle and the benighted solitary bee. Blister beetles live in the southwestern deserts of the United States. Females lay their eggs in grassy patches where solitary bees forage. The beetle eggs all hatch simultaneously, and the thousand or so newborn larvae immediately gather together into a tight formation. They form a nice oval shape, all dark and fuzzy. They travel as an inseparable unit, up and down the blades of grass. They look and act just like—a female solitary bee. Before long, they start releasing a pheromone mimic, and now they smell like a female bee too. A male bee lands on what he thinks is a mate, and the blister pack clings to him en masse. Disappointed by the encounter, and seemingly unaware of his cargo, the male bee flies on in search of new love. Should he find and approach a real female bee, the beetle larvae will instantly abandon him and cling to her. The female will take them where they want to go, back to her well-provisioned nest. The larvae will deplane, settle down, and gorge themselves to maturity on nectar, pollen, and, best of all, the bee's eggs.