Chances are, you’re familiar with the many things said about daddy longlegs. Maybe you’ve heard that that these curious creatures are spiders—or that they’re so venomous that humans are lucky their fangs are too short, or too weak, to do much damage. Spoiler alert: You shouldn't believe everything you hear. To find out more, Mental Floss spoke with Ron Clouse, who has been studying the DNA and lineages of these often misunderstood arachnids for more than a decade. "I do everything from going into the field and collecting them to analyzing the data and doing the papers and all the lab tests in between,” Clouse told Mental Floss in 2014. Here's what you should know.
1. Daddy longlegs aren’t spiders …
Yes, they’re arachnids, but they’re actually more closely related to scorpions than they are to spiders. They don’t produce silk, have just one pair of eyes, and have a fused body (unlike spiders, which have a narrow “waist” between their front and rear).
2. … And they’re not venomous.
That thing you heard at summer camp about daddy longlegs being the most poisonous creature in the world, but with fangs too weak to bite you? Not true. They don't even have fangs, and they can't make venom, either. According to Clouse, the rumor might have gotten started during “the retelling by an American tabloid of a study in Australia on the venom of a daddy longlegs there; the problem is that in Australia, ‘daddy longlegs’ refers to a type of spider,” also known as the cellar spider (Pholcus phalangioides). And, if that's not confusing enough, there's another creature that sometimes goes by the name daddy longlegs: The crane fly.
3. They’re very, very old.
“We know from a very well preserved fossil of a daddy longlegs from Scotland that they are at least 400 million years old,” Clouse said. “This fossil actually looks a lot like the long-legged species we see today. It is believed daddy longlegs split off from scorpions, which were becoming terrestrial about 435 million years ago. To put this in perspective, this is about 200 million years before dinosaurs appeared, which were only around for about 165 million years.”
4. Daddy longlegs go by a few other names.
In North America, the reason for at least part of their name is pretty obvious—the species we see most frequently have very long, thin legs. But there are different names for them around the world. “In other regions, their common names reflect different attributes found in the species common to those areas," Clouse said. "So, the large, short-legged forms in South America are often referred to by their pungent odors. In Europe, terms like ‘harvestmen’ and ‘shepherd spiders’—and even their scientific name, Opiliones—refer to them as being associated with good pasture, harvest season, or perhaps even their resemblance to shepherds on stilts or the shape of a scythe.”
5. They’re found all over the world.
These arachnids can be found on every continent but Antarctica. “They’re usually found in humid areas, such as under rocks, in leaf litter, and inside caves,” Clouse said. “They are most diverse in tropical areas, where the moist climate and thick foliage allow them to live in lots of places. Different regions of the world have their own particular daddy longlegs, and some of the most common ones are small and out of sight in the leaf litter on the forest floor. Even here in the U.S. we have some tiny ones in the leaf litter that the average person never sees.”
6. Daddy longlegs come in many different varieties.
There might be as many as 10,000 species of daddy longlegs, with 6000 to 7000 currently described. “We’re describing new ones all the time,” Clouse said. “They are generally very, very bad at getting around, so they tend to have lots of species, because the minute a river flows between two different populations or a mountain rises and cuts one population off from another population, they split into two new species.” For example, the closest relatives to the arachnids he studied in South Carolina live in West Africa, which were all one species before the continents split and the Atlantic Ocean sprang up between them.
Because of this tendency to split off into new species, daddy longlegs can look very different depending on where they live, and each species will have a very small range: “One mountain top will have one species, another mountain top will have another species,” Clouse said. In Pennsylvania, they have tiny pod-like bodies and long legs. The type that Clouse studied, called cyphos, are tiny and have short, thick legs. In Laos, a species with a legspan of 13 inches was discovered in 2012, while those in the family Gonyleptidae, which live in South America, have spines and vibrant colors. “They have so many strange aspects, it's difficult to think of a type that isn't interesting,” Clouse said.
7. Sometimes daddy longlegs hang out in big clumps.
This clumping is pretty typical daddy longleg behavior, Clouse said, and though scientists don’t know for sure why they do this, they do have some ideas. “Perhaps they do this when conditions become dry and they need to maintain high humidity,” he said. “Perhaps they are ‘herding’ to lower their individual chances of being eaten. Or perhaps they are trying to bolster their chemical defenses.”
8. They don’t get around.
You would think that creatures with legs like these arachnids have would move around quite a bit, but that’s not the case. DNA sequencing populations of long-legged species near the coast of Brazil revealed that “they do not get around at all. They don’t go anywhere,” Clouse said. “Their day is something like this: They’re in a crevice until about 7 o’clock, when they come walking out and they sit on a leaf all night long. And then when the sun starts to come up, they’ll walk back to the crevice. Those long legs are apparently all for male-male competition, or showing off to females, because they don’t use them.”
As for why they don’t travel much, Clouse said that “it’s some kind of fundamental trait they have about their need for humidity, their own behavior in terms of feeding and mating. Of course, after 40 million years, you’d expect someone to evolve the ability to just get up and get around. But they really don’t.”
9. Daddy longlegs have interesting ways of dealing with predators.
Birds, frogs, and lizards frequently make meals of daddy longlegs. The arachnids have a few strategies for not becoming lunch, including the aggregation mentioned above. “Their most obvious feature to avoid predation is to produce chemical excretions from glands on their bodies, which have been observed to repulse predators,” Clouse said. “Daddy longlegs are usually extremely well camouflaged. During the day many of them hide in crevasses, and when disturbed they usually curl up and remain motionless for several minutes.” Yes, they play dead—which works extraordinarily well for a couple of reasons. “First of all, if you’re living in a leaf litter with dirt and debris and little pieces of deadwood, they’re exactly the right color brown—they truly just disappear,” Clouse said. “For a lot of predators, if something stops moving, they can’t see it anymore. It just disappears for them. When these guys stop moving, they’re gone.” You can see a video that Clouse made of a cyphos playing dead here.
10. They clean up.
Many species do something called leg threading: “They slide one leg at a time through the little pincers by their mouths,” Clouse said. “Other species may groom themselves in other ways, but in general this behavior is very important to keep parasites off the body. You can see small red mites on many of them in places that they can’t reach.” You can see a daddy longleg leg threading in the video above.
11. They can live for a long time.
The bigger species, like the kind Clouse studied in Brazil, tend to live for less than two years, but the tiny cyphos can probably live for up to seven years. “You can’t really tell by body size how long they’re going to live,” Clouse said. “But unlike a lot of insects, many can survive several seasonal cycles as an adult. The most ephemeral ones are probably the long-legged ones we see in the U.S., which, after a few months as a juvenile, often live only a few more months as an adult.”
12. Their legs don’t grow back.
If you were one of those kids who plucked off one of these creatures' legs, prepare to feel a little guilty: Those things do not grow back. “We see injured ones—they’ll have an article cut off on the end. They probably got bitten by something,” Clouse said. “But in general, when something with an exoskeleton gets injured, they can’t do very much until the next molt happens.” And daddy longlegs, once they’re fully grown, don’t molt anymore. “I presume that if an immature daddy longlegs, what we call a nymph, lost a leg or had an injury, it could very well get repaired,” Clouse said. “When it molts again, it would be deformed, but there would be at least another leg starting or developing there. You’ll often see the big, long legged ones with six legs or seven legs. They can’t regenerate like a starfish.” That’s bad news for species that voluntarily shed legs to get away from predators or in species where males fight and attempt to break off their opponents' hind legs with their large spines.
13. We don’t know if daddy longlegs are predators or scavengers.
“In the field, where these big ones are, the frustration of my colleagues is that they always seem to come upon them already eating something!” Clouse said. “It’s hard to tell if they caught it or if they just ran across it. Here’s the bottom line: They don’t have fangs, they don’t have big strong pincers. Some of the little ones do seem to have muscular pincers, which allows them to grab and crush some little tiny, tiny bugs in the leaf litter. But except for a few families of them, most of them just don’t seem to be equipped to do much hunting. So we assume they just nibble on pieces of carcass, leftovers, and detritus. Not a very exciting diet.”
14. Much of their reproductive cycles are still a mystery.
Certain species—like the cyphos that Clouse studied—are so small and hard to spot that no one really knows about their mating rituals or how many eggs they lay. “All we do know about those little seed-like ones is that, in many cases, the males have special glands that the females don’t have,” he said. “It seems like they make some kind of chemical that they spread around to attract females.”
Here's what we do know about how cyphos does it: “The male creates a packet of sperm and he extrudes and he gives this spherical package to the female,” Clouse said. What happens next, though, isn’t clear. “She probably opens the package up and takes the sperm inside; it’s kept alive [until] the sperm goes into her reproductive tract somewhere, where it meets the eggs and fertilizes.” Then, the female uses a telescoped ovipositor longer than her body to lay the eggs deep in the dirt.
The mating rituals of bigger species are much easier to observe, and Clouse has gotten an eyeful. “I’ve seen some big ones in Brazil mating and it’s pretty elaborate,” he said. "There’s a lot of him going up to her and touching her and her kind of making a lot of decisions about what’s going on here." Most daddy longlegs species "mate with the male depositing sperm inside the female," Clouse said. "What she does with it and how all their parts interact is still not entirely clear." Once, Clouse and his fellow scientists observed a big female in Brazil that had just laid 30 slime-encased eggs on a leaf. "She produces a concentrated substance, which, when it hits the moist air, expands and makes this really nice jelly," he said. "It probably keeps fungus and stuff off."
15. The males and females can be pretty different … except in the case of “sneaky males.”
“In [some] species, males have much longer legs than females,” Clouse said, “and in others males have glands or protuberances not found in females. What these are used for is not known.” But some species have two types of males, Clouse said, “ones which are very distinct from females, and others which are very similar to females. Presumably the latter ones can sneak close to females and obtain matings without engaging in brutal competition with other males.”
It’s not as weird as it sounds; Clouse said it happens in a number of animals where there’s a lot of competition between males that is driven by female choice. In fish, for example, these males will “have the coloration of a female, the size of a female, but they’re not female,” Clouse said. “They sneak by all the other males. They get right by them all, right next to the females and next thing you know, she’s releasing eggs, he’s releasing sperm and the deed is done.”
In daddy longlegs, regular males are called alpha males, while the males that look like females are called beta males. In all systems with alpha and beta males, there are never that many beta males in the population at any one time. “You can never have more than a certain proportion of these sneaky males,” Clouse said. “If they get to be too frequent, then they’re bumping into each other and the alpha males have an advantage. Females still like big strong males, and so these sneaky males tend to remain a certain percentage of the population over stretches of time. And if a female has the gene to produce lots of sneaky males, she has an advantage when there aren’t a lot of sneaky males. And if more are around, the trait to make sneaky males becomes less frequent in the population. It fluctuates back and forth around a certain percentage.”
Regardless of whether a male is an alpha or a beta, it will still have the same objective. “They seem to have all the urges,” Clouse said. “They want to mate with females, they just don’t look male.”
16. Scientists found an amber-encased male daddy longlegs in a delicate position.
Described in 2016, the Halitherses grimaldii specimen, which was trapped in tree sap 99 million years ago, had an erection. Discover described its penis as being nearly half as long as the creature's body and having “a distinctively heart-shaped head and a twisted tip, meant for delivering sperm to females via a hole near their mouth,” noting that it was “the first [harvestman] to be discovered in such a, well, unique position.” Because the penis is usually held within the harvestman's body, scientists speculated that the creature had either recently mated or that “the harvestman may have gotten his erection while locked in a struggle with the sticky resin, raising his hemolymph, or blood, pressure enough that his penis hardened.”
A version of this story ran in 2014; it has been updated for 2022.