Arachnids: Vinegaroons

This post is the sixth in an ongoing series on arachnids. Previously, this series addressed whipspiders, hooded tickspiderspseudoscorpionsharvestmen and solifugids. 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 vinegaroon.

By now, if you’ve been reading my continually-updated series on the underappreciated and less diverse groups of arachnids, you will have been exposed to an assembly of bizarre creepy-crawlies; among them, “headless” hooded tickspiders, library-squatting pseudoscorpions, manic, ever-hungry solifugids, family-oriented amblypygids, and amputation-prone harvestmen. Weird as these groups all are, few compete with the strangeness of the arachnids known as “whipscorpions”, “uropygids”, or “vinegaroons.”

These arachnids are members of the order Thelyphonida, a small group of arachnids comprised of only 100 species, dwarfed by larger orders like the Araneae (spiders, with more than 40,000 species) and the Scorpiones (“true scorpions”, with about 1,700 species). The order used to be incorporated in a now defunct classification known as Uropygi (which also included small, close relatives known as “microwhipscorpions”). “Uropygi” basically means “tail rump” or “tail rear” in Greek, which refers to the arachnids’ curious, thin, segmented “tail” extending from the back of their abdomen. It is this tail, or “whip”, combined with their general scorpion-like body shape, which is key to the origin of one of their common names; the “whipscorpion.” They are also known by their third common name, used frequently throughout the Americas, “vinegaroon”, which alternatively sounds like the most foul tasting Girl Scout cookie ever.

“Oh…oh god. What have I done?”

While vinegaroons have a scorpion-like body shape, with their flat, extended abdomens and spiky, clawed pedipalps (those pincer appendages in front of the face), they are not closely related to scorpions at all. As far as we can tell, they are most closely related to things like amblypygids and spiders, and are in a separate subdivision from things like scorpions, camel spiders, and daddy-longlegs, which make up a proposed grouping called Dromopoda.

Vinegaroons are found in the warmer latitudes of North America, throughout Central and South America, as well as subtropical and tropical Asia (and a lone species found in tropical Africa). The center of their diversity appears to be in Southeast Asia. They, in true arachnid form, like to hunker down in humid, dark places, which usually requires clawing out a burrow in the dirt with their pedipalps. Many species are found in forest habitats of varying moisture, but some live in arid habitats. One of these is the largest species of vinegaroon, Mastigoproctus giganteus, with a body about as long as a credit card, which lives comfortably in the desert and semi-arid tracts of the southern U.S. and Mexico, but tends to only be active during the wetter months of the year.

Vinegaroons are entirely nocturnal, and emerge from their dank holes in the earth nightly to stalk hungrily and ominously over the Land of the Tiny. They are exclusively carnivorous, and feed primarily upon other arthropods, like crickets, cockroaches, and millipedes, which they pin down with their beefy, scorpion-like, wire-cutter pedipalps. They are also equipped with a sharp spine on the inside surface of the claw, which is more or less a barb, immobilizing the prey and paving the way for the merciless crushing of their prey’s brittle exoskeleton, allowing the vinegaroon to leisurely lap up the critter’s hemorrhaging fluids like a cat at a water dish.

The hard part, though, is finding the food in the first place. Vinegaroons have eight small eyes, two at the front of the head segment (the prosoma) and three flanking each side, but the eyesight they provide is so fucking poor the worthless things might as well be pimples. To make up for their myopic failings, vinegaroons successfully navigate their witching hour escapades by tactile mastery. They, much like their distant cousins the camel spiders (solifugids), only use their hind three pairs of legs for walking; their front pair have evolved into long, thin, highly-sensitive feelers that scan the ground in front of the vinegaroon. It would seem that somewhere early in its evolution, the vinegaroon must have looked at insects and their antennae with much envy, because these modified front limbs look like the imitation, off-brand version of what everything from beetles to bumblebees have been proudly waving around on their heads for eons. In this way, vinegaroons sense their environment similarly to their close relatives, the amblypygids, using their delicate front limbs as a pair of white canes. Further contributing to sensory input is their “tail”, a long, straight, segmented rod (also referred to as a “telson”, which is a term also used for the “tail” of crustaceans like lobsters and shrimp). The telson is used to feel around at the back of the animal, and surely functions as an adaptive safeguard against the “Kick Me” sign prank.

But woe be unto those who dare to stray too close to the vinegaroon’s caboose. These arachnids don’t have the venomous bite of spiders at the front, nor the deadly sting of scorpions at the back. Their pedipalps can deliver a bit of pinch, and the worst their telson can do is give a gentle tickle. It would appear as though the vinegaroon is something of a sitting duck, nothing but a helpless, crunchy, eight-legged chicken nugget for the world’s passing raccoons and lizards to casually inhale. But the vinegaroon has a unique trick up its sleeve geared towards keeping it unharassed and uneaten.

The vinegaroon is a squirter.

Vinegaroons are armed with glands located right at the junction of the rear body segment (the abdominal segment, or “opisthoma”) and the base of the telson. These glands (the “pygidial glands”) produce a liquid mixture of a number of chemical compounds, but the stuff is primarily acetic acid and caprylic acid in many species. You may know acetic acid as the key ingredient in vinegar, which is essentially 5% acetic acid by volume, which gives it its sour taste and characteristic odor. When threatened, vinegaroons jettison the watery contents of these glands through a pair of pivoting turrets, mounted on either side of the base of the telson in a spurt that can each about a foot away in any direction. With just enough agitation, the vinegaroon contracts the muscles around its dual tanks, and lets the cocktail loose, sending a wild, flailing stream of vengeance arcing through the heavens, like some drunk bastard using a urinal during an earthquake. It is the resulting noxious stink from these acidic emissions, reminiscent of common, household vinegar, that is at the origin of the “vinegaroon” name. The smell is particularly strong due to the concentration of acetic acid in the spray, which can be 15 times more concentrated than in vinegar. The video embedded below shows how this spraying looks up close, at around 2 minutes in:

I can hear the scoffing already. Really? That’s the defensive response? A stinky water gun? What’s it going to do, turn an attacker into a pickle? Some scorpions, like those of the “man-killer” genus Androctonushave such horrifically venomous stings, that a defensive strike can incapacitate or kill animals as large as humans. Some spiders, like the Sydney funnel-web, can potentially deep-six your ass if it insists on getting bitey. But the vinegaroon’s so-called “defensive behavior” has all the ferocity of an infirm chihuahua dribbling on a carpet. Other arachnids can do wonderfully nasty, painful things to get predators to turn tail…while this firehose-assed jackoff over here is what, adding zest to a salad at Olive Garden? What would a vinegaroon-themed supervillain even do? Terrorize reservoirs of baking soda sitting underneath paper mâché mountains?

“Oh, human, you will rue the day you picked up the Sprinkle Master…prepare to be….wetted…”

The vinegaroon’s pungent piddling isn’t just an uncomfortable distraction; it is actually a well-honed deterrent. For one, the dual flesh faucets that spray the jet of chemicals can be rotated in just about any direction, and can quickly be aimed relatively accurately in the direction of a harasser. The goal isn’t to get the predator to wrinkle its nose and recoil at the sour stink, but to get the ass spritz into the eyes, nose, and mouth. This is a strategy not unlike what spitting cobras employ for dissuading aggressors. The spray, in most species, isn’t concentrated enough to do much to skin, especially if that skin is covered in fur. But the acid mixture is irritating to mucous membranes, and a shot of this crap in the mug will go over like lemon juice eye drops and jalapeno mouthwash. The shit burns.
There’s also evidence of the presence of 2-ketones in the sprays of some species of vinegaroon, specifically 2-heptanone, 2-octanone, and 2-nonanone…all of which can function as potent organic solvents. The presence of these solvents (which help dissolve organic compounds, like the acetic acid, in other organic compounds…which includes everything you are made out of) in the sprays has shown to increase the effectiveness of the acetic acid, with the spray actually managing to briefly sting human skin. The 2-ketones act as an “enhancer” for what is normally a benign acid for large animals.

If the proctological can of Mace doesn’t work, there’s always good, old-fashioned claw clappin’ and scrappin’. The pedipalp pincers aren’t deadly to anything larger than a house key, but a nip on the face of a lunging mammalian assailant might be enough to convince them to reconsider. When threatened, vinegaroons will normally strike a defensive pose with their pedipalps outstretched and ready to tussle, with their opisthoma and telson arched, prepared to turn on the Pain Sprinkler.

“Come at me, bro. I can do this aaaallllll fucking day.”

Assuming these blind, wizzing wizards fend off enough toothy jaws with their stanky squirts to make it to adulthood, they can get right on with the baby making…but not before an arduous courtship display.

Vinegaroons engage in an exhausting, complicated, 13+ hour-long marathon of multi-stage foreplay prior to getting on with the rogering. It starts off with roving male encountering a female, and him chasing her down and grappling her with his pedipalps. The two of them then appear to spar with one another, gripping, shoving, and throwing each other around. It’s so….sweet? This bit of love wrasslin’ can be cut short at around a minute, or this stage, which may function as an evaluation of “worth” in a partner (“is he/she a good, strong mate?”), can continue for hours. If the female is receptive to a, errrr, “second date”, she’ll signal that they can proceed by sticking her first pair of sensory limbs in the mouthparts of the male and wiggling them back and forth. This acts as a “tap out”, and the couple proceeds to the next step in their relationship. At any point prior to this, she may signal that she’s not down to clown, and with a subtle, aggravated flick of her sensory legs, she peaces the fuck out and courtship ends.

The second phase involves dancing. Not even joking. The male still grips her delicate sensory limbs in his mouthparts (“chelicerae”), and, face to face, he drags her around, back and forth, using his muscular pedipalps. The female follows his lead, continuing to evaluate him as a mate. The sensual display is akin to something out of Dirty Dancing, except this version of the mambo has Jennifer Grey’s fists wedged deep in Patrick Swayze’s mouth. This part lasts somewhere on the order of three or four hours.

“Nobody puts Baby in a burrow.”

If both partners are still ready to continue towards the finish line, the male while have typically edged the two of them into a safer location (like a burrow). The male, still with the female’s sensory legs embraced by his mouthparts, rotates so that he’s now riding on top of her. They stay like this, poised awkwardly over each other like players in a game of Twister, for another several hours. During this time, the male manufactures a spermatophore (a dense sac of sperm) inside of his abdomen. When this is over, the male deposits his payload on the dirt in the form of rigid block of reproductive material. He then carefully maneuvers the female over the spermatophore, and takes the two attached sperm packets from the spermatophore framework, and shoves them into the female’s gonopore (genital opening). When the female is ready, she signals by opening her clawed pedipalps, and the male promptly releases her legs from his mouthparts, and wheels around to grasp her soft abdomen. For the next few hours, the male massages the sperm packets with his pedipalps, and it is thought that this helps the sperm actually disperse into the female’s reproductive tract. Eventually, the deed is done, and they uncouple and go their separate ways. Unlike in many other arachnid groups, post-coital cannibalism doesn’t really seem to be a thing in vinegaroons. After a casual boinking with a disproportionately passionate preamble, they mutually part paths.

The female then carries fertilized eggs inside of her for a few months. Before laying as many as three dozen eggs, she seals herself up in a burrow for safety. However, instead of laying a clutch that sits on the floor of the burrow, she contains them in the sac that adheres to the bottom surface of her opisthoma. She continues this voluntary house arrest for another few months. Did I mention that she refuses to eat? And that she arches her abdomen in such a way that the giant broodsac can’t touch the ground? FOR MONTHS. Say what you want about the difficulties of human gestation and what our mothers went through in pregnancy to birth all of us…but mama vinegaroons endure the equivalent of carrying around a garbage bag full of bowling balls with nothing but your clenched ass cheeks for an entire college semester.

“Oh, you do Kegels? That’s cute.”

Eventually the eggs develop into “post-embryos”, which is a name that doesn’t adequately illustrate how much these larval creatures look like albino, baby, gummy squids.

Tapioca pearls with legs. Lovely.

These baby vinegaroons climb onto their mother’s back, where they latch on for dear life with sucker-like organs. There they remain for yet another month. Eventually, they have their first molt, and begin to disperse away from the mother and begin foraging upon small insects and mites. Once seasonal rains arrive, and the young have all managed to develop hardened exoskeletons, the mother, famished, bursts out of her subterranean cocoon to get her fat reserves back up again. Much like their relatives, the whipspiders, vinegaroons engage in a higher level of maternal care than what is seen in many other arachnid orders. The mother will abstain from eating her babies unless in dire need of sustenance, and cohabitates with the young, first-molts in the burrow for a short while. Whether or not the mother, in nature, actually provides food for the young during this time is not currently known.

Thelyphonida, an enigmatic and rarely encountered order of arachnids, is represented by a single family in modern times. The vinegaroons are an ancient group, with fossilized, relatively unchanged representatives stretching back 350 million years (in the Carboniferous era), 100 million years before the earliest dinosaurs strode Earth. Today, only a small number of species are still around. These dark, glistening, hard-shelled, silent travelers of the night quietly assist in reducing numbers of pests like cockroaches and termites. These acrid skunks of the arachnid world are oddities, with their trifecta of sensory feelers and unusual acetic acid nozzles, and while they might appear dangerous or foreboding, if you are so lucky to encounter one in the wild, remember that the worst these little guys can do to you if you get too close is stink up your shoes.

Image credits: Intro image, vinegaroon in hand, defensive vinegaroonvinegaroons dancing, female vinegaroon carrying broodsac, vinegaroon with post-embryo young

© 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.

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10 thoughts on “Arachnids: Vinegaroons

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  3. A truly great article and video…I have captured vinegaroons in the past and had always thought they just exuded the liquid which then covered their bodies for protection. The odor carried several feet away but I had never actually see the creature spray and was unaware of it’s ability to do so. Even when capturing a vinegaroon and have the liquid deposited on my hands I had not experienced the ‘squirting’ effect. A first for me!!

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  7. Those things are nasty looking! Had to kill one in the office one day when one wandered in and my co-worker nearly had a panic attack. Also, the name of your website is awesome.

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