Arachnids: Harvestmen

This post is the fourth in an ongoing series on arachnids. Previously, this series addressed whipspiders, hooded tickspiders, and pseudoscorpions. Additional posts on other weird, often overlooked or neglected groups of these creepy crawlies to follow. For a related chelicerate, but as far as science can tell, not an arachnid, see the post on sea spiders.

The harvestman.

In the U.S., Canada, and the U.K. they are generally referred to as “daddy longlegs.” Less often, they are given the name “shepherd spiders”…not because of an adoration of our wooly, farm animal friends, but because their conspicuously long, spindly legs are reminiscent of how, back in the day in Europe, shepherds used stilts to get a better vantage point for watching their flocks…because in those times, people used tools at their jobs that are, today, relegated for the “circus arts” or whatever the fuck the Oregon Country Fair is.

More often than not, we tend to encounter harvestmen in relatively unflattering settings (dusty corners of garages or sheds, beneath untended vegetative landscaping, suburbia in general) and doing unflattering things, like clumsily wobbling off in a direction very loosely resembling “away” from you, teetering along like an intoxicated pre-teen who grew too fast for their coordination to catch up. Within the scope of our lives, harvestmen are no more than the arachnids of unswept places, with vaguely unsettling, Slender Man-like proportions. However, these thread-legged critters are far more interesting and diverse than most of us are aware of, and make up a unique group of arachnids that is regrettably seen as only a curious afterthought amid the dust bunnies and the nooks and crannies of exposed building foundations.

Before addressing these awesome little nuances of harvestman biology, it’s perhaps helpful to get something out of the way: what harvestmen ARE and what harvestmen ARE NOT.

The most important thing to understand from the get-go is that harvestmen are not spiders. They may have the eight, long legs, the roughly circular body suspended in the middle, and overall size and appearance one would associate with spiders, but harvestmen are a different beast altogether. Sometimes, in nature, something that looks like a duck, walks like a duck, and quacks like a duck…is actually a chicken in a Daffy Duck costume. Harvestmen are spiders in the same way that Senator Mitch McConnell is a Galapagos tortoise…through a superficial, yet striking, exterior resemblance and nothing more.

Harvestmen are arachnids that belong to entirely different order from spiders; they are members of the Opiliones (which comes from “opilio”, which in Latin means “shepherd”) rather than the spider order of Araneae. Not only are they in separate taxonomic groups, these groups aren’t even particularly closely related to one another. The order Opiliones is thought to be closely allied with the groupings comprising the scorpions and their closest relatives (like pseudoscorpions and the so-called “camel spiders”), together forming a subclass of arachnids known as the Dromopoda. Generally speaking, a precursory examination of these little guys can lead someone to see the most obvious differences between harvestmen and spiders; harvestmen have body segments fused at a broad juncture into a bean-shaped structure covered in folds of exoskeletal armor, whereas spiders have two easily-defined segments (or “tagmata”)…harvestmen also have a pair of tiny, simple eyes on top surface of the center of their body, while spiders have an array of different types of eyes all at the front of their head region (the “cephalothorax”).

If you are at all familiar with harvestmen (especially if you grew up in the United States) you are almost assuredly acquainted with a frustratingly commonly shared bit of jarringly dramatic “natural history” about their supposed venomous bites. The meme is typically thrown around on playgrounds, where harvestmen are frequently encountered in the warmer months, between children, who relay the idea that harvestmen are “the most venomous animals on the planet” but have mouths and/or fangs too small to adequately pierce human skin, so are of no danger.

This claim sits about as far from reality as you can get. Harvestmen do not only produce not a single drop of venom, they also don’t possess the mouthparts (fangs) that would allow them to envenomate anything anyways. Unlike spiders, harvestmen chelicerae (the appendages in Chelicerates like arachnids that loosely form the mouthparts used to apprehend, dispatch, and process prey items) are segmented and end in minuscule pincers instead of giant, hollow spears anchored to a swollen venom gland. These mouthparts are used to delicately carve up food, like a pair of blunt embroidery scissors, into pieces small enough to fit into their mouth hole. Harvestmen “bites”, when they rarely occur, are more “pinches” than anything else, and are about as deadly as a lick from a puppy.

Harvestmen are perfectly capable arachnids in their own, humble way, not the powerful killers of urban legend, plagued by impotence.

“Sleeping too much? Trouble catching prey, or satisfying your mate? You don’t need to suffer in shame. Ask your doctor about ChelicaMax. Feel like a harvestMAN again.”

If there are any arachnologists reading this right now, I expect there are some chuckles arising at the irony of my cheap erectile dysfunction jab at harvestmen. You see, if there’s any arachnid that doesn’t deserve to be associated with…er…”underwhelming” expressions of manhood, it’s those tall drinks of water found in the Opiliones. Male harvestmen are unique among arachnids because they are the only arachnids to possess a penis. Most arachnids make sweet, creepy-crawly love to one another using “indirect” copulation, which involves the coordinated transfer of a kind of “sperm packet” into a pore in the body of the female…which is less like familiar, human-style sex and more like plugging a tailpipe with a snowball. Harvestmen get down in the “direct” way, with funny looking interlocking components and everything. And by saying harvestmen penises are “funny looking” I mean they look absolutely fucking terrifying. Decorated with a complex assortment of spines, loops, and tendrils, harvestmen dongs look more like something that would slither out of slimy egg sac and slowly kill off B-list actors interstellar, spaceship-bound explorers than…you know…genitalia. For an animal that has legs that are about as flimsy as a human hair, it certainly packs a disconcertingly authoritative member.

Suddenly, the “daddy” in “daddy longlegs” makes me far more uncomfortable than it used to Credit: Sue Lindsay, Australian Museum

Yes, the arachnid that looks like nothing more than long pieces of dried grass stuck to a booger has a dick shaped like an angry, strike-ready cobra.

In addition to this, some species of harvestmen are actually parthenogenetic, meaning that the entire species is female, and reproduces without fertilization from a male (that’s right, some species of “daddy longlegs” have no actual daddies to speak of)…and with males running around with serpent doom-Johnsons primed and loaded, I can’t blame the ladies for going solo.

But of course, for the harvestmen…er…men (I’m a fan of shortening that to “harvestbros”), their pelvic thrust is far worse than their bite. I mean that in regards to their purely mythical venom, and to the unusual way in which harvestmen feed themselves in the first place. To you, me, and anyone other than Charles Bukowski, an entirely liquid diet seems like an odd venture to indulge in. Yet, it is how all arachnids ingest their food; spiders liquefy the insides of their prey with their slurry of digestive enzymes pumped through their fangs, slurping the juicy mixture back in the same way…scorpions dribble digestive goo Brundlefly-style all over their lunch, then suck up the resulting puree of tissue afterwards. Mites feed on liquefied plant cells or animal skin cells. Ticks gorge themselves into red, ballooning, gluttonous oblivion on blood. But harvestmen alone among their arachnid kin feed on the tough stuff, solid food, cutting up pieces of whatever they can find, be it an insect, small frog or other vertebrate, or even a mushroom, and immediately placing it into their digestive tract. This menu by itself is incredible, considering that all other arachnids are either predatory or parasitic, and harvestmen have a varied diet largely encompassing scavenged material from the dead, dung, and plants and fungi. You might think that in the land of the baby food-eaters, the steak-eater is king, but dining on solid pieces of food make harvestmen more susceptible to infection with a number of internal parasites and pathogens (most of these being intestinal nematode worms and pathogenic fungi, both of which can strike their hosts dead) that other arachnids don’t have to deal with, as their liquid, pre-digested diet screens out a lot of these organisms.

Diseased or not, anything that eats hornets is automatically a friend to me.

Harvestmen can bumble through this world alone if they so wish, but many species are very comfortable associating closely with other members of their species, sometimes in large numbers. Harvestmen can congregate in great, dense balls, typically in some protected location near water. In temperate latitudes, this most often occurs with the cool, autumnal approach of the winter months, aligning with the time of the agricultural harvest (hence the common name “harvestman”). Some of these aggregations can reach unreal sizes (reportedly in the tens of thousands of individuals), blanketing rock overhangs or tree trunks, looking like a particularly unkempt patch of pubic hair…that is, until it is disturbed, leading to an exodus of very confused little stick figure fuckers all over the place. Observe the video below, which showcases these living, colonial shag carpets and a pure, uncut hit of the heebie jeebies:

So, you might be saying to yourself, harvestmen a) don’t have venomous bites, b) eat a balanced diet like their mommas taught them to and c) cuddle together in great, shudder-inducing mats, making them easy targets for birds or other predators to shit themselves in excitement and coat their insides with the biggest buffet in their truncated little lifespans….why again are these goody two-shoes, with their apparent lack of defenses, not extinct? Not only are they not extinct, there are 6,500 species currently recognized in the Opiliones, and it’s likely that this only describes half of the actual diversity of harvestmen on Earth. They are a very old and successful group of arachnids, stretching back well over 400 million years, and they appear to have changed jack shit about their biology in that period of time; fossilized species dating back more than 100 million years before the first dinosaurs are barely distinguishable from modern harvestmen. So what’s their secret to even the most limited level of survival in the brutal, roiling pot of nature, where everything is trying to eat everything else, poop it out….and then eat it all over again?

For one, harvestmen have a few behavioral tricks up their long, long sleeves. Some species, when encountering a predator, sway their bodies erratically on their wiry legs. This bit of unpredictable movement is, understandably, unnerving, and often the predator is too befuddled to attempt messing with the dancing harvestman. Many species also engage in “autotomy”, which is where an animal sheds an entire body part, like a limb or a tail (as in many lizard species) in order to distract a predator, allowing for a quick getaway. In autotomous harvestmen, the gangly legs are what are cast aside in a pinch; at the junction of the “hip” the limb is severed, and the harvestman wobbles away as fast as the remaining seven legs can take it. This strategy’s effectiveness is boosted by another unique feature of harvestman biology; their respiratory system. Unlike most other arachnid groups, harvestmen don’t have book lungs, the folded structures that perform gas exchange in spiders, scorpions, etc., but instead breathe through small holes and tunnels running in and out of their exoskeleton; tracheae. Many have spiracles (holes) that allow for air to enter on each of the legs. If one of these legs is kicked to the curb in a permanent sense, it still retains a small part of the respiratory system. In many autotomous animals, the lost body part thrashes and twitches violently for a short while to keep the attacking predator’s attention long enough for the escape to be a success. The harvestman’s leg continues to draw oxygen into all of the tissues of the limb for a great while after being disconnected from the body, nourishing excited nerve fibers with fresh oxygen, and letting the disembodied limb, ala the Addam’s Family’s “Thing”, move around, deceivingly, for many minutes later.

Despite a slight shot to their over-land fleetness (and maybe a case of phantom limb syndrome or two), harvestmen seem to use this anti-predator strategy frequently (many harvestmen are found with seven or fewer legs), competently temporarily evading death by means of the world’s most gruesome take on the Hokey Pokey.

“Self-amputation is what it’s all about, kids.”

Another defensive measure commonly used is a little less subtle. Rather than stupefying with killer dance moves, or putting on a literal, live rendition of My Left Foot, harvestmen can also turn themselves into a meal that spurs on acute contrition for the unwary diner. Most harvestmen have specialized glands, called ozopores, located at the sides of the front of the “head” region (called the cephalothorax in many arachnids, the “prosoma” in harvestmen). These glands, derived from simple scent glands, secrete a rank fluid concoction that is repellent to both the nostrils and the taste buds. When compressed or harassed, the harvestman squeezes the noxious fluid out of the sides of its body with muscular contractions, and the chemical blend presents itself as milky droplets seeping out behind the folded chelicerae.

“I come from a long line of longleg milkers. It’s a dying art.”

Modified from Chemical defense of an Opilionid (Acanthopachylus aculeatus) . Thomas Eisner, Carmen Rossini, Andres Gonzalez and Maria Eisner . 2004. Journal of Experimental Biology 207, pp. 1313-1321.

A major chemical component of these secretions is benzoquinone, a toxic compound that smells like heated or melting plastic, mixed with an over-chlorinated swimming pool, and if it gets pretty much anywhere on you, the effects are fucking nasty, interfering with oxygen transport if ingested (along with lots of weakness and vomiting) and irritating the sensitive membranes of the mouth and nose, blistering exposed skin and eyes. The overall effects of the chemical secretions, and their effectiveness as deterrents vary significantly between species of predator, as well as the species of harvestmen, as the makeup of these poisonous cocktails differ enough between groups of harvestmen that they can be highly informative when it comes to identifying species, or classifying newly discovered ones.

All of these weird traits, the purposeful loss of legs, the caustic armpit drippings, the shoulder-to-shoulder-to-seven-other-shoulders congregations of a number of individuals that exceeds the maximum capacity of most Division I football stadiums, are all well and good, but harvestmen aren’t exactly the most interesting things to look like. All of them have the same, simple construction; spindly legs, nondescript, oval-shaped body, tiny eyes, and barely discernible chelicerae. Even the most colossal species of harvestman, with legs so long it could hug a throw pillow, looks the exact fucking same. More or less, they all look like a spider sketched by an artistically-challenged 3-year old. Little ball, lots of long, skinny sticks attached.

Right? Wrong.

Most of the harvestmen encountered by folks living in the temperate Northern Hemisphere and greater Anglophonic world (also the major audience of this blog; don’t worry, I check my visitor stats, I’m very aware most of ya’ll are from the West) appear this way. Most of these species also belong to a single sub-order of Opiliones, the Eupnoi, which contains about a fourth of all described species of harvestman. However, the bulk of harvestman biodiversity is situated in the sub-order Laniatores, with about 4,000 species. These harvestmen, which have their highest numbers in the humid forests and caves of the subtropics and tropics (particularly in South America), tend to look very different from their European and U.S. cousins. Many species have thick-plated body armor, surreal proportions, nefarious-looking thorns and projections, and….well…you’ll see what I mean if you just look…

This adorable little bucket of terror is Soerensenella prehensor, native to New Zealand. It’s a member of the Triaenonychidae family of harvestmen, which are found chiefly in North and South America, Madagascar, Japan, and Australasia. They are characterized by their relatively short legs, and grotesquely expanded pedipalps which resemble a pair of ice cream scoopers that someone covered with crazy glue and dunked in a dish of thumb tacks. It’s thought that these crampon-lined bear-huggers are used in the same fashion as the lightning-fast, weaponized front legs of a praying mantis; to ambush and spear prey, bringing it close to those hungry mouthparts, effectively impaled into submission by a thorny embrace.

Oh, what now? A Headcrab with rickets?

Some tropical Lanitorian species of harvestmen look like the Pokemon “evolutions” of smaller, scrawnier versions of the arachnids. An example of this is the hulked out, walking Dali painting above, Pachyloidellus goliath, and it is found in high-altitude areas in Argentina. The swollen body and studded armor plating might be intimidating, but it has more renown due to its particularly odoriferous ozopore secretions. The smell is apparently so repulsively offensive, that in the local Quechua language, it is called “chichina”, which is in loose reference to another endemic arthropod that defends itself with a stinky discharge, a relative of stick insects (Agathemera crassa) which is called “chinche molle.”

There are alien-looking harvestmen outside of the Laniatores as well. Some are nested right within the supposedly “familiar” Eupnoi group. For example, there’s the harvestmen of the genus Megalopsalis found in New Zealand, which have males with outlandishly overgrown, 2-segmented chelicerae that they keep tightly folded up like a pair of butterfly knives during most of their day.

“All the better to creep you out with, my dear.”

Chelicerae among females are pretty standard, so, although not much is known about these guys, it’s likely the ridiculously giant mouthparts have some history in sexual selection. They could be for male-male competition, in the same vein as bull elk that clack antlers together. Or it may be directly tied to female mate choice, where no fighting is involved, but the males showing off the most preposterous chelicerae (or rather, the males healthy enough to grow and maintain such cumbersome body parts) are scored as a particularly good date and/or father of many multitudes of larval children.

Finally, there are some members of the sub-order Dyspnoi that deserve mentioning, a small group of less than 400 species of harvestman found only in the cool latitudes of the Northern Hemisphere and are thought to be closely related to the Eupnoi cluster of species. One species of harvestman within the Dyspnoi is a shining-star example of the evolution of weird dietary specialization. It is Ischyropsalis hellwigi, native to central Europe, and it eats snails and other molluscs (scientists think exclusively so). If you are wondering how it manages to do so, seeing as how snails have protective shells (kind of a big part of being a goddamn snail) and how typical harvestmen have the kiddy scissor version of chelicerae, and even the elongated examples I pointed out above don’t seem to have any real power behind them…might as well try to crack a coconut with a back-scratcher….you’d be correct to be skeptical. Luckily, both sexes of I. hellwigi look like they’ve been taking syringes of nandrolone in the ass for years on end, and are gifted with the some of the planet’s most ‘roided out harvestman chelicerae, period.

Schwarzenegger up there has a taste for escargot, and those lobster-like claws, bulging with muscle inside their exoskeletal prison, are the perfect tools for the job. There hasn’t been really any record of these harvestmen eating snails in the wild, but that might be more due to the fact that they are very much nocturnal and aren’t exactly common…so stumbling across one of these arachnids isn’t likely in the first place, let alone one in the middle of a meal. In captivity, however, these wanna-be prawns go ape shit over being introduced to snails and slugs, which they dispatch immediately with a cold, calculated method of deconstructing the snail’s happy little mobile home. It apparently involves propping the shell up with one powerful chelicera, and then chipping off fragments of shell with the other claw, incrementally whittling down to the prize at the core, like the world’s most patient consumer of a fortune cookie. Eventually, the mollusk’s soft body is reached, ripped through the harvestman-carved window in the shell, and greedily devoured. These harvestmen are also known to take down slugs and snails multiple times their mass, because these are apparently arachnids with not even the faintest trace of a fuck to give.

Whether they are bobbing their way out of getting wolfed down by a lizard, clambering over the forest floor 400 million years ago, or looking like warty alien spiders that stepped right out of an Avatar rendering, harvestmen represent an amazing and diverse order of arachnids. Perhaps most exciting? We still know almost nothing about the huge numbers of opilioids that have been discovered, particularly the bizarre forms that hide quietly in the equatorial rainforests. We are only now starting to understand the chemical composition of their defensive ozopore secretions, and seeing as how there is an unusual level of variation between families of harvestman on what types of compounds are produced, and a high number of active products (sometimes nearing 100 or so compounds), there is a plenty of opportunity to discover chemical compounds that, if co-opted and adapted, might serve humankind well in the areas of medicine or industry.

Image credits: Intro harvestman, harvestman closeup in grass, harvestman with hornet abdomen, harvestman with white background, Sorensenella, Pachyloidellus, Megalopsalis.

© Jacob Buehler and “Shit You Didn’t Know About Biology”, 2012-2014. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jacob Buehler and “Shit You Didn’t Know About Biology” with appropriate and specific direction to the original content.


14 thoughts on “Arachnids: Harvestmen

  1. “For example, there’s”….
    Hey! You can’t leave me hanging like that!!!!
    Great article, love your writing. (Except the ending 😉 )

  2. Pingback: Arachnids: Solifugids | Shit You Didn't Know About Biology

  3. Huge fan of the website! My favorite blog by far. Two questions:

    1. Have you ever considered writing for Cracked? It would definitely help boost popularity to your site. Your writing style would be very warmly accepted there
    2. Have you considered expanding beyond just this site? Like doing Youtube videos or something? It’s just a shame that not as many people get to see this great content
    3. Is there any possibility of making it easier to access the full breadth of your website? The only easy way to see your older articles that doesn’t require endless sifting through the calendar is looking through your top pages. Would you ever consider putting in a more accessible index or perhaps even a random article button considering how many you have?

    • Thanks! Glad you’re enjoying the blog.

      1. Yes, actually. I’ve been considering it for a while. Actually, much of this blog was inspired by what Cracked has been putting out for years. I imagine that before the year is over, I’ll put out a pitch to them. Same thing for Slate’s Wild Things series of blog posts. Keep on the lookout!
      2. Not particularly. Vlogging has never really been a medium I’ve been very comfortable with. I’m hoping that I can get more exposure through doing more science writing for sites with a larger audience base, at least as a primary measure. Writing is where my core strength is, and I don’t have the media expertise to set up a decent, entertaining video as of yet.
      3. Yes, I actually just scrapped the calendar completely and replaced it with a dropdown archive, which I think might be more manageable. Also, I added a category listing so you can see what subjects have been addressed in posts past, as well as the ten most recent posts. I got rid of the “top pages” widget because I’m not sure it’s that informative.

      Thanks for your suggestions!

  4. Great article! Hilariously written, it’s nice to see Harvestmen get some attention. Looking forward to your vinegaroon feature (I figure they’re on the list)

    One quick correction…spiders don’t actually suck things up with their fangs, they’ve got a weird little mouth. Totally blew my mind when I found that out.

  5. Pingback: Arachnids: Vinegaroons | Shit You Didn't Know About Biology

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  7. Good article. I used to play with “daddy longlegs” when I was a kid. I do remember, they must have thought I was a threat, because they would lose a leg here and there. Very interesting that it is used in the same way as the tail of a lizard, to distract the predator.
    Really enjoyed the article. Thanks.

  8. Don’t mind the fact that I only found this 4years after you wrote this hilarious and super informative blog about one of my favorite creepies! I am beyond thrilled to find out more about these skittish corner hoarders. I really enjoy the way you convey your knowledge – Thanks the refreshing view. I’m certainly in for a productivity decline as I peruse your other posts 😀

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  10. This is the best thing I’ve ever read. I am simultaneously fascinated and utterly creeped out by harvestmen now, thank you. Someone will see me pointing a magnifying glass at the dudes in the grass and think I am insane (I mean it’s not like they’d be wrong). You will be responsible for significant work delinquency as I’ll now be going through all your articles instead of working. Or sleeping.

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