The Merry Pranksters
Story by Paul Wood
Photo by David Liittschwager
But the truth about this spider (which has a far more serious scientific name, Theridion grallator) is more interesting, more puzzling and—yes—more lovable than appears at first glance. The happyface spider is one of the many reminders that the native Hawaiian wilderness is chock full of information about evolution, genetics and biology. An endemic Hawaiian species, it is found nowhere on Earth except in the undisturbed upland forests of O‘ahu, Maui, Moloka‘i and Hawai‘i Island. It is common around Thurston Lava Tube at Hawai‘i Volcanoes National Park.
Just five millimeters long—less than one-fifth of an inch—the happy-face spider likes to live on the underside of a single leaf, which it rigs with a slight, almost invisible web. It sleeps by day and gets active at night, darting forth to grab infinitesimal insects, which it consumes in the usual spidery way by liquefying its prey with digestive juices and then slurping the results.
The happy-face spider belongs to a large spider family called Theridiidae. These spiders build cobwebs—loose, tangled constructions—and include a variety of house spiders, most notoriously the black widow. But the happy-face, nonaggressive by nature, is utterly harmless to gigantic mammals like us.
Dr. Rosemary Gillespie has published several scholarly works about that puzzling face and its implications for the study of evolution and genetics. Her interest in the spider dates back to the 1990s when she was a zoology professor at the University of Hawai‘i at Mänoa, and it has continued as she fulfills her many present duties at UC Berkeley: professor in the Department of Organisms & Environment, holder of the Schlinger Chair in Systemic Entomology and director of the university’s seventyyear- old Essig Museum of Entomology. Despite her ability to write papers in the arcane language of real science, she retains a fine ability to explain basic concepts in plain phrases, which she brightens with the crisp tones of her upbringing in Kirkcudbrightshire, Scotland.
“In every population it seems that about two-thirds of the spiders are plain yellow, almost translucent,” she says. “The remaining third are all different colors— red in front, red in back, white all over, a whole pile of different colors.” In other words, not all of the happy-face spiders have happy faces. Most are plain yellow, though one-third of them morph into a wide range of colors and patterns, some of which result in smiley faces.
Gillespie looked for the “trigger to make this work”—in other words, the evolutionary reason that this was occurring— and focused on the birds that search for and eat the little spiders. As the birds pick their way quickly through the forest vegetation looking for snacks, they react to “search images” by pecking away at all the samelooking ones. So, according to Gillespie, the happy-face pattern gives the spider a “confusion factor. The effect is to stop the birds from developing a search image.”
Perhaps that gives spiders a chance to scurry out of range. Perhaps it just forces hungry birds to think, feel frustrated and move on. Either way, this color adaptation, however the spiders create it, works with the birds. And perhaps it will work with humans, too, if Homo sapiens feel more inclined to protect the Theridion grallator habitat because they feel all moist-eyed and cheerful about a little spider that has a goofy grin on its back. Ultimately perhaps the happy-face spider will illustrate a new Darwin-esque principle: the survival of the smiliest.