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15 Fascinating Facts About Daddy Longlegs

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Being a curious person can be a double-edged sword. On one hand, you learn so much! On the other, you sometimes find yourself looking up arachnids right before bedtime, as I did earlier this month. When my search turned up some really interesting information on daddy longlegs, I had to know more—so I called Ron Clouse, who has been studying the DNA and lineages of these often misunderstood arachnids for 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," he says. Here are a few fascinating facts he told us about daddy longlegs—which I now find pretty cool.

1. THEY’RE NOT 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. 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 says. “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. THEY HAVE 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 says. "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 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 says. “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. THEY COME IN MANY DIFFERENT VARIETIES.

Gonyleptes fragilis, from the Atlantic rainforest in Brazil. Photo by Ron Clouse.

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 says. “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’s studying 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 says. Where I grew up in Pennsylvania, they have tiny pod-like bodies and long legs. The type that Clouse studies, 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 says.

7. SOMETIMES THEY HANG OUT IN BIG CLUMPS.

You’ve all seen the Vine, where a guy pokes what appears to be a huge tangle of hair and—surprise!—a bunch of daddy longlegs spring forth and run at the camera. (And if you haven't seen it, it's embedded above.) This clumping is pretty typical daddy longleg behavior, Clouse says, 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 says. “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.

Pachyloidellus goliath, native to Argentina. Photo by JovenGandalf via Wikimedia Commons.

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 says. “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 says 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. THEY HAVE INTERESTING WAYS TO DEAL 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 says. “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 says. “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 says. “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 male Opilio canestrinii leg threading in the photo series 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 species he’s currently studying can probably live for up to seven years. “You can’t really tell by body size how long they’re going to live,” Clouse says. “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 says. “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 says. “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 THEY’RE 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 says. “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 studies—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 says. “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 says. 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.

Neosadocus maximus mating. Photo by Ron Clouse.

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 says. "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 says. "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 says. "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 says, “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 says, “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 says 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 says. “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 says. “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, Clouse says: “They seem to have all the urges. They want to mate with females, they just don’t look male.”

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Big Questions
Should You Keep Your Pets Indoors During the Solar Eclipse?
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By now, you probably know what you’ll be doing on August 21, when a total solar eclipse makes its way across the continental United States. You’ve had your safety glasses ready since January (and have confirmed that they’ll actually protect your retinas), you’ve picked out the perfect vantage point in your area for the best view, and you’ve memorized Nikon’s tips for how to take pictures of this rare celestial phenomenon. Still, it feels like you’re forgetting something … and it’s probably the thing that's been right under your nose, and sitting on your lap, the whole time: your pets.

Even if you’ve never witnessed a solar eclipse, you undoubtedly know that you’re never supposed to look directly at the sun during one. But what about your four-legged family members? Shouldn’t Fido be fitted with a pair of eclipse glasses before he heads out for his daily walk? Could Princess Kitty be in danger of having her peepers singed if she’s lounging on her favorite windowsill? While, like humans, looking directly at the sun during a solar eclipse does pose the potential of doing harm to a pet’s eyes, it’s unlikely that the thought would even occur to the little ball of fluff.

“It’s no different than any other day,” Angela Speck, co-chair of the AAS National Solar Eclipse Task Force, explained during a NASA briefing in June. “On a normal day, your pets don’t try to look at the sun and therefore don’t damage their eyes, so on this day they’re not going to do it either. It is not a concern, letting them outside. All that’s happened is we’ve blocked out the sun, it’s not more dangerous. So I think that people who have pets want to think about that. I’m not going to worry about my cat.”

Dr. Jessica Vogelsang, a veterinarian, author, and founder of pawcurious, echoed Speck’s statement, but allowed that there’s no such thing as being too cautious. “It’s hard for me to criticize such a well-meaning warning, because there’s really no harm in following the advice to keep pets inside during the eclipse,” Vogelsang told Snopes. “It’s better to be too cautious than not cautious enough. But in the interest of offering a realistic risk assessment, the likelihood of a pet ruining their eyes the same way a human would during an eclipse is much lower—not because the damage would be any less were they to stare at the sun, but because, from a behavior standpoint, dogs and cats just don’t have any interest in doing so. We tend to extrapolate a lot of things from people to pets that just doesn’t bear out, and this is one of them.

“I’ve seen lots of warnings from the astronomy community and the human medical community about the theoretical dangers of pets and eclipses, but I’m not sure if any of them really know animal behavior all that well," Vogelsang continued. "It’s not like there’s a big outcry from the wildlife community to go chase down coyotes and hawks and bears and give them goggles either. While we in the veterinary community absolutely appreciate people being concerned about their pets’ wellbeing, this is a non-issue for us.”

The bigger issue, according to several experts, would be with pets who are already sensitive to Mother Nature. "If you have the sort of pet that's normally sensitive to shifts in the weather, they might be disturbed by just the whole vibe because the temperature will drop and the sky will get dark,” Melanie Monteiro, a pet safety expert and author of The Safe-Dog Handbook: A Complete Guide to Protecting Your Pooch, Indoors and Out, told TODAY.

“If [your pets] have learned some association with it getting darker, they will show that behavior or at a minimum they get confused because the timeframe does not correspond,” Dr. Carlo Siracusa of Penn Vet Hospital told CBS Philly. “You might put the blinds down, but not exactly when the dark is coming but when it is still light.” 

While Monteiro again reasserts that, "Dogs and cats don't normally look up into the sun, so you don't need to get any special eye protection for your pets,” she says that it’s never a bad idea to take some extra precautions. So if you’re headed out to an eclipse viewing party, why not do your pets a favor and leave them at home. They won’t even know what they’re missing.

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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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