If you grew up in the United States, you’ve probably heard a peculiar story about daddy longlegs. That is, daddy longlegs—which look like tiny, pink beans, supported by eight impossibly thin legs—are actually the most poisonous spiders in the world. Fortunately, given how common these creatures are, they’re harmless because their fangs are too small to pierce the skin. You know this, and have probably known it for a long time. And nearly everything about it is wrong.
At La Selva Biological Research Station in Costa Rica, a scientist maneuvers a daddy longlegs with the calm exactness of a judo master, holding a single delicate leg and smoothing it along the edge of a ruler. She has the heroically unkempt look of a field biologist, her reddish-brown hair expanding to a puff of curls in the tropical humidity. Her nose ring and wooden sloth earrings convey equal parts punk-rocker and nerd, leaving an impression of confident contradiction. Leticia Margarita Classen Rodriguez—who goes by Leti—is well into her third month of study at La Selva, the flagship research station for the Organization for Tropical Studies.
People see daddy longlegs “and call them spiders,” Leti says. “They’re not. They don’t have venom.” In fact, they belong to an entirely different order of arachnids, called Opiliones, or harvestmen. Harvestmen are more closely related to ticks than spiders and have two tiny eyes, rather than the eight that spiders have. They also don’t build webs or even make silk. But they do produce a slightly stinky substance when disturbed. Leti holds her test subject out for me to smell. It’s a faint, musty odor, with the slight olfactory equivalent of a static charge. She takes a deep inhale and smiles mischievously. “I like the smell.”
Leti has come to La Selva from the University of Puerto Rico, where she will soon earn her bachelor’s degree with a double major in Environmental Science and Ecology. She came to Costa Rica through a program called Research Experience for Undergraduates (REU), funded by the National Science Foundation. When asked about the challenge of traveling to a foreign country to do independent research, she becomes very serious for a moment. She’s momentarily tongue-tied as she tries to explain the conflicting emotions. “I just can’t believe it,” she says, adding that she’s never been out of Puerto Rico for so long. “I think it’s amazing. I’m out here, I have no one, basically.” She laughs as she describes her mother’s impression of what she does: She tells friends that her daughter “lives in the forest, she’s hunting spiders.” Leti sometimes argues with her parents about the long hours, the distance, the danger posed by venomous snakes and insects. “Sometimes they don’t like hearing about it, because they can’t deal with it,” she says. But overall, she is driven by immense curiosity and love for the natural world.
“I love my island. But I know there’s so much more out there,” Leti says. She describes her aspiration to explore and learn about the world. With her passion for tropical studies, she intends to bring her expertise back home. She says, “I want to learn so much so I can go back and do something significant on my island.”
And at 22, she is already contributing to science. For her project, Leti is trying to understand the consequences of what scientists call autotomy; that is, what happens when you lose a limb to avoid being eaten? If a bear got hold of one of your arms, would you give him the arm in order to escape? This is exactly what many animals, such as spiders, harvestmen, and lizards do. But unlike spiders, which can grow legs back, and lizards, which regenerate tails, harvestmen do not regrow their jettisoned limbs. Instead, they have to find food, mates, and avoid being eaten, all with one less leg. Leti wants to know how the loss of a leg affects the ability of male harvestmen to force females to mate with them.
In the information age, where any random fact can be sought out in seconds, harvestmen seem luxuriant in their foreignness. Their range extends from the tropical lowlands of Costa Rica, where Leti collects her test subjects, to the high latitudes and urban settings where you may have noticed and ignored them. And you’re not alone in ignoring them. Leti’s study species is common at La Selva, an area of intense research that produces on average one scientific paper every 2.5 days. Yet, even here, her “babies” don’t even belong to a named species; they are known only as Prionostemma species #1. “Maybe it’s because they’re so small, maybe people don’t think they’re really significant,” she says. She admits that harvestmen don’t have any direct applications to human health, which likely plays a role in their relative obscurity.
Yet Leti’s research touches on an epic drama of minute proportions, which has been playing out for millennia. Among sexually reproducing animals, females want to mate with the best male they can in order to pass his superior genes on to their offspring. They may also get a little pampering from a good mate; in Leti’s study species, some males perform a little post-coital mate grooming. But things are not always rosy. Broadly speaking, the male strategy is to mate with as many females as possible. When females aren’t interested, males may attempt to mate by force. The commonness of such “forced copulations” in ducks has led to an arms race in which females evolve increasingly maze-like vaginas, and males riposte by evolving longer, ever more improbably shaped penises. We know less about such arms races in harvestmen. But Leti is running an experiment to address this gap in our understanding. Her experimental design will determine whether, if she causes a male to drop a leg, this makes him less attractive to females. Does it affect his ability to force females to mate? And vice versa—if a female loses a leg, does this make it harder for her to refuse a determined male?
A bright smile splits Leti’s face as she shows me a group of her harvestmen test subjects. They’re clustered in a plastic deli dish, legs intertwined, bouncing in a vaguely cartoonish manner. “They’re so cute.”
There is this mysterious world, which scurries about unnoticed underfoot. It is amazing. Many of us struggle to understand the point of spending time and resources on something that has nothing to do with human health, or has no perceived economic value. Leti says, simply, “If they’re there, why not study them?”
What will we learn if we follow Leti’s example: if we focus our attention on the quotidian mysteries lurking in our periphery? What will we find scurrying under our frenetic pacing, struggling, proliferating, swirling in a world of unexpected intricacy, hidden in plain sight?