In nature, the spider and hairstreak come into contact when the butterfly lands on leaves or flowers to rest and feed. The species of hairstreak butterfly and jumping spider used in the experiment are both common in the southeastern U.S., with similar relatives spread worldwide. Most importantly, the spider is very small, so sometimes its prey is 10 times larger." The spider has an innate or acquired ability to distinguish the head region very well and it always attacks there to deliver its venom to the vital center to instantly paralyze the prey. "In one video, the spider sees a moth that looks like a leaf and it walks very carefully around to the head and then jumps at the head region. "From the video, you can see the spider is always very precise," Sourakov said. Sourakov videotaped the experiments and analyzed the results in slow motion. 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'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. "It's a big step in general and a big leap of faith to realize that a creature as tiny as a jumping spider, whose brain and life span are really small compared to birds, can actually be partially responsible for the great diversity of patterns that evolved out there among Lepidoptera and other insects." "Everything we observe out there has been blamed on birds: aposematic coloration, mimicry and various defensive patterns like eyespots," said study author Andrei Sourakov, a collection coordinator at the Florida Museum of Natural History's McGuire Center for Lepidoptera and Biodiversity on the UF campus. The research published online March 8 in the Journal of Natural History shows small arthropods, rather than large vertebrate predators, may influence butterfly evolution.
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.
Since the time of Darwin 150 years ago, researchers have believed large predators like birds mainly influenced the evolution of coloration in butterflies.
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