Forget that urban myth, the daddy longlegs is a harmless arachnid on stilts.
Illustration by Robert Meganck
Perhaps you’ve heard that the daddy longlegs is the world’s most poisonous spider, but that it can’t bite humans because its fangs are too small. Let’s clear up a few points on that: 1) The daddy longlegs has no fangs; 2) It’s not poisonous; 3) It’s not even a spider.
“That’s a complete myth,” says Victor Townsend, professor of biology at Virginia Wesleyan University. “They don’t have any poison glands. They don’t have fangs.” In fact, says Townsend, their most offensive defense is literally raising a stink. “If you handle one for a bit, you will start to notice this noxious scent.”
Townsend has handled plenty in his career, being a keen scholar of the daddy longlegs—or, as they are known more commonly worldwide, and among scientists, “harvestmen” (because just to confuse matters, the colloquial name “daddy longlegs” in some places is used instead to refer to the long-legged crane fly and in some other places to refer to a long-legged, house-dwelling, also-harmless actual spider, the longbodied cellar spider).
In taxonomy, daddy longlegs belong to the same class as spiders (arachnids), but an entirely different order known as “opiliones,” Townsend explains. “Opiliones” derives from the Latin word for shepherd, “opilio,” apparently in a nod to shepherds in a certain region of southern France who once used to go about on stilts (the better to keep vantage over their sheep, so the story goes).
Unlike spiders, daddy longlegs don’t have the capacity to produce silk. Their bodies are “externally fused”—which is to say that while in a spider you see two distinct regions of the body, in opiliones you see no external division. Instead of fangs, daddy longlegs have “little claw-like mouthparts.” And while most spiders are carnivores, says Townsend, harvestmen are omnivores. “They are generalists as far as their diet,” he says. “They will scavenge, they will eat little insects like termites or springtails, they will eat mushrooms and fruit. I have seen them eating bird droppings, all kinds of things.”
“They are one of the few arachnids that can ingest solid food particles,” says Townsend. “They rip off little pieces of their food and ingest them.” Townsend adds that if you are the prey of a daddy longlegs, this can’t be an entirely pleasant way to go.
“If you are getting eaten by a daddy longlegs, you are getting eaten alive, ripped to pieces and shoved in the mouth,” he says.
That grim note aside, daddy longlegs possess a notable defensive strategy for when they themselves are on the dinner menu, called “autotomy,” Townsend explains. “They have a joint between the two leg segments close to the body that when they are grabbed they can sever. And the detached leg will twitch for up to an hour to distract a predator so the daddy longlegs can get away.” Neat trick, though unfortunately, says Townsend, they can’t grow the leg back.
The name “harvestmen” was likely given to this order of arachnids for a reason you yourself may have noticed: You are most likely to observe their presence in the late summer and early fall—the harvest season—when you might find them hanging out on a bedroom wall or marching determinedly across your living-room floor.
This is the time of year when harvestmen in Virginia are mating and laying their eggs, says Townsend. It’s also when they are largest in size. For much of the rest of the year, they are present but smaller, and often living in the soil and leaf-litter where they aren’t particularly visible.
They are, however, sometimes quite startlingly visible when they engage in a behavior known as “aggregating,” where the individuals are touching, sometimes overlapping legs and even bodies, for reasons not yet clearly determined by researchers.
Sometimes two or a few might aggregate, but in some places you might find many, many, many more. “In the tropics I have seen thousands of individuals in multiple layers,” says Townsend. You can prod an aggregation and the harvestmen will scatter; YouTube has on offer a number of videos of very large aggregations looking rather like a hairy outcropping on a cliff or wall until the enterprising videographer pokes at the mass.
Townsend says that you will sometimes also see whole aggregations moving in place in a kind of bobbing motion. “When you get hundreds of individuals doing that all together, it is really creepy,” he says, “so that could be some benefit for group defense.”
Townsend did not plan on being a serious student of harvestman. In fact, he planned to be a herpetologist. But, he says, “I went down to research in Trinidad 12 years ago to study snakes, and didn’t find any snakes—but I found a lot of harvestmen.”
Biologists, he says, “are always looking for interesting questions,” and when it comes to harvestmen, “there is so much more to learn about them that we don’t know.”
This article originally appeared in our December 2016 issue.
