Not All Heroes Wear Capes, but These Termites Did for Science
The researchers started by collecting plain-looking termites from the wild. Then they pasted pieces of paper to their backs that more or less looked like capes — either solid black, solid white or striped in black and white.
This was not the latest effort to introduce tiny heroes to the Marvel Cinematic Universe. It was an attempt to learn something about how jumping spiders, some of nature’s most widespread and canny predators, perceive their prey.
In nature, most prey avoid being detected by predators by blending into their surroundings. But some species strive to stand out. Monarch butterflies, yellowjacket wasps and ruby-red velvet ants, for example, use bright or contrasting coloration to warn predators of their toxicity.
Scientists are still trying to decipher which predators perceive such displays. Especially little is known about how jumping spiders process these color patterns. According to Lisa Taylor, a behavioral ecologist at the University of Florida, they possess keen vision thanks to a set of large, forward-facing eyes.
To determine how two species of jumping spiders react to vibrant warning signals, Dr. Taylor and her colleagues outfitted termites in capes fit for scientific cosplay and put them in a petri dish with the eagle-eyed arachnids. Their findings, published on Wednesday in the journal Royal Society Open Science, reveal that while the spiders quickly spotted the termites in the striped capes, they rarely attacked the striped termites, providing an explanation for why myriad other species use striking stripes to scare off predators.
Most prior research on how predators perceive aposematic or conspicuously colorful displays has revolved around carnivorous birds. But the majority of species with such patterns are small insects. This means that they likely evolved their visual defenses in response to arthropod predators, like arachnids.
That’s where jumping spiders come in. With more than 6,500 species found worldwide, jumping spiders are voracious arachnids that feed on just about any invertebrate they come across. They also possess diverse visual capabilities. While most have good vision, some species can see colors, including those commonly used in visual defenses, like reds and oranges.
Dr. Taylor and her team studied two species of jumping spiders commonly found in Florida — the regal jumping spider, or Phidippus regius, and Habronattus trimaculatus. While P. regius only sees two colors, H. trimaculatus sees three. P. regiusalso has a stronger immunity to prey toxins, making H. trimaculatuspotentially more wary of attacking brightly colored prey.
The researchers placed two termites of each cape variety in a petri dish with a jumping spider and recorded which termite the spiders looked at and which they ended up attacking.
They found that P. regiusroutinely spotted termites with striped and solid black capes first. However, the spiders attacked termites in striped capes far less than they did those wearing black or white. H. trimaculatusalso showed a proclivity to spotting termites in striped capes first. But these spiders ultimately proved much pickier, attacking termites roughly half the time that P. regius did.
The new findings suggest that many jumping spiders may inherently be able to pinpoint striped patterns. In earlier studies, Dr. Taylor discovered that another jumping spider species spotted termites with striped patterns faster than those with yellow or gray colors. A different species attacked termites in striped capes less often than those that were wearing gray capes.
“Stripes always do something,” Dr. Taylor said. “They’re either capturing attention or reducing attack or doing both.”
This may illustrate the effectiveness of stripes at grabbing a predator’s attention.
“Stripes enhance the internal contrast,” said Tom Sherratt, an evolutionary ecologist at Carleton University in Ottawa who studies how flies mimic the black and yellow patterning of wasps to deter predators, but was not involved in the current paper. “Sometimes just being a single color, like yellow or red, isn’t sufficient to improve your conspicuousness — you need a contrast.”
Dr. Taylor thinks conspicuous stripes’ ability to both attract attention and deter attacks is why the pattern is so common in nature. “If most jumping spiders pay attention to stripes it’s a pretty good strategy because jumping spiders are everywhere,” she said. Several insect species with striped coloration overlap with thejumping spiders in the paper, including monarch caterpillars, treehopper nymphs and cucumber beetles. When it comes time to avoid being eaten, stripes are always in fashion.
