Butterflies are among the most vibrant insects, with colorations sometimes designed to deflect predators. New University of Florida research shows some of these defenses may be driven by enemies one-tenth their size.
Since the time of Darwin 150 years ago, researchers have believed large predators like birds mainly influenced the evolution of coloration in butterflies. In the first behavioral study to directly test the defense mechanism of hairstreak butterflies, UF lepidopterist Andrei Sourakov found that the appearance of a false head – a wing pattern found on hundreds of hairstreak butterflies worldwide – was 100 percent effective against attacks from a jumping spider. The research published online March 8 in the Journal of Natural History shows small arthropods, rather than large vertebrate predators, may influence butterfly evolution.
Sourakov’s behavioral experiments at the McGuire Center showed the Red-banded Hairstreak butterfly, Calycopis cecrops, whose spots and tail imitate a false head, successfully escaped all 16 attacks from the jumping spider, Phidippus pulcherrimus. When 11 other butterfly and moth species from seven different families were exposed to the jumping spider, they were unable to escape attack in every case. Sourakov videotaped the experiments and analyzed the results in slow motion.
Unlike other butterflies, hairstreaks constantly move the hind wings that carry the false head pattern, a behavior that seems to increase in the presence of the spider, as if the butterfly is attracting attention to itself, Sourakov said. In museum collections, hairstreak specimens are frequently found with the false-head portion of the wings missing. During the experiments, the spider always attacked the butterfly’s false head, thereby avoiding its vital organs.
“The false head hypothesis in hairstreaks has been in circulation for a long time because people always speculated that their tails move around in order to fake out the predators, but there was little experimental evidence,” Sourakov said.