What You Didn’t Want to Know About Part III: Sexy Legs – Ricinuleids

The arachnids belonging to the order Ricinulei, or hooded tick spiders, are neither spiders nor ticks. At first glance, these primitive arachnids look a lot like your typical spider. However, if you look closely you will notice that they have segmented abdomens unlike spiders and a complete lack of eyes. It’s like they were trying really hard to cosplay as a spider but missed most of the critical details on their costume. Even so, you’ll probably never have to worry about making this distinction because ricinuleids are rare in comparison to other arthropods. Though locally abundant, only 55 species worldwide have been identified since the order’s discovery in 1838 and specimens are few and far between. A fossil of an extinct Carboniferous species was found in 1837, but the guy who found it thought it kind of looked like a beetle, so it wasn’t identified as a ricinuleid until later. Extant species are found in tropical regions of Central America and western and central Africa where they live in soil and litter.


“I can’t decide what I want to be, so I’ll be everything!”

Very little is known about this animal group even today, but scientists do know that males use their modified third pair of legs for sex. That’s important. Not just because it’s funny, but because looking at ricinuleid junk can be critical to species identification. These legs are used to hold and then transfer seminal fluid into a mounted female’s genital opening. Females store the sperm for later when they are ready to fertilize their eggs. The eggs are laid singly and sometimes carried around by the mother that laid them. Interestingly, baby ricinuleids hatch with only six legs instead of the usual eight that is the signature of arachnids. This and other morphological features is shared with Acari, or mites and ticks, and is believed to be indicative of a close relationship with that order. As the young develop, they grow their final pair of legs and start to look more like proper arachnids.


This is what the female gets stuck up her lady parts…

If you are so inclined, this paper has an even better picture of the male pedipalp: http://www.scielo.br/pdf/zool/v29n5/v29n5a12

Why are they called “hooded” tick spiders? The spider and tick parts of the common name are understandable, as they look a bit like spiders and are related to mites and ticks, but what about them is hooded? As it happens, ricinuleids have a cute little hood on their heads called the cucullus that can be raised or lowered at will. When the hood is down, it covers their mouthparts completely. How polite! The purpose and function of this structure is not yet understood, but it is one of their most defining features.


“I’m not going to show you my mouth because that would be rude.”

Ricinuleids may not be as fierce looking as amblypygids or as cool as vinegaroons, but they’ve been around the block and certainly have their own special quirks. So give them a round of applause for just sticking with it and existing all these years. If any order goes unappreciated, it’s the hooded tick spiders.

1. Harvey, Mark S. Catalogue of the smaller arachnid orders of the World: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO publishing, 2003.

2. Harvey, Mark S. “The neglected cousins: what do we know about the smaller arachnid orders?.” Journal of Arachnology 30.2 (2002): 357-372.

3. Adis, Joachim U., et al. “On the abundance and ecology of Ricinulei (Arachnida) from Central Amazonia, Brazil.” Journal of the New York Entomological Society (1989): 133-140.

4. Ewing, H. E. “A synopsis of the American arachnids of the primitive order Ricinulei.” Annals of the Entomological Society of America 22.4 (1929): 583-600.

5. Platnick, Norman I. “A new Cryptocellus (Arachnida: Ricinulei) from Brazil.” Journal of the New York Entomological Society (1988): 363-366.

6. Talarico, G., J. G. Palacios-Vargas, and G. Alberti. “The pedipalp of Pseudocellus pearsei (Ricinulei, Arachnida)–ultrastructure of a multifunctional organ.” Arthropod structure & development 37.6 (2008): 511-521.

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What You Didn’t Want to Know About Part II: Smells Like Vinegar – Uropygids

The order Uropygi (Thelyphonida) contains animals that are essentially really buff scorpions with whips on their butts instead of stinger tipped tails. They are often called whip scorpions for this reason. Another popular name for uropygids is vinegaroon because they use this whip to spray a mixture of acetic acid (vinegar) and other compounds when threatened or harmed. Their bodies are bulky and well armored, with powerful crushing structures on their pedipalps. These spine-like protrusions are used to capture and hold prey before tearing it apart. Similar to amblypygids, their elongated first pair of walking legs are held out in front to help with navigation. All of these features can make vinegaroons appear larger and scarier than they actually are, at least to us. The largest species in the world, Mastigoproctus giganteus, only reaches a maximum length of 3.3 inches, which is not huge compared to other arachnids.


“Do you think you’re tough enough to take me on?”

Fearsome as they may look, vinegaroons fit with our running theme of tender arachnid sex. When it’s time to make babies, the male gently grasps the female’s antenniform legs and then turns around so that they are both facing the same direction. He deposits a spermatophore on the ground and then grabs it, turns around again, and places it into the female during an abdominal embrace. She can then fertilize her eggs and will lay them within a few months. To do this, she digs a burrow and seals herself inside. Eggs are laid into a sac on the underside of her abdomen, which she holds aloft so as not to drag the eggs on the ground when moving. She does not eat during this time, which is impressive because it can take several months for the eggs to develop and hatch. Newly hatched vinegaroons ride on their mother’s back until their first molt.


Arachnid sex in action!

Most species from this order inhabit tropical regions, but a few, like M. giganteus, live in arid desert environments like many of their true scorpion cousins. M giganteus can be found in the American Southwest and Mexico where it serves an important role as a predator of pests such as cockroaches and crickets. This vinegaroon was the subject in a study by Schmidt et al. (2000) to better understand the composition of the spray. It was often believed that vinegaroon secretions contain formic acid in addition to acetic acid, but this is false. The study analyzed the fluid within the pygidial glands of vinegaroons of different ages and sexes and found that none contained formic acid. The major components of vinegaroon spray are acetic acid, which gives it the strong vinegar smell, octanoic acid, and water. The purpose of this fluid cocktail was also reevaluated in the study. It was only ever used in self-defense, and even then only if that vinegaroon was directly attacked. It appears as though predators are not deterred by being sprayed inside the mouth. However, any contact with sensory tissue such as the eyes, skin, or an arthropod’s feelers can be irritating enough to put off the attacker. In one particular trial, the researchers placed a sulfugid (camel spider) in with a first instar (between first and second molt) vinegaroon and it got a face full of spray. After that, it ran around the cage frantically trying to clean its face with sand and refused to touch another vinegaroon after that. Adult vinegaroons have little to fear, for they are powerful predators themselves and have tough armor to protect them. In the event that they are attacked, though, the spray is an effective way of letting the predator know to back off.

These animals demonstrate that you don’t have to be big, aggressive, or venomous to make it in this world. When faced with danger, you don’t have to fight. Just be really irritating and maybe you’ll be left alone!

1. Schmidt, Justin O., et al. “Chemistry, ontogeny, and role of pygidial gland secretions of the vinegaroon Mastigoproctus giganteus (Arachnida: Uropygi).” Journal of insect physiology 46.4 (2000): 443-450.

2. Rowland, J. Mark, and John AL Cooke. “Systematics of the arachnid order Uropygida (= Thelyphonida).” Journal of Arachnology (1973): 55-71.

3. Harvey, Mark S. Catalogue of the smaller arachnid orders of the World: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO publishing, 2003.

4. Harvey, Mark S. “The neglected cousins: what do we know about the smaller arachnid orders?.” Journal of Arachnology 30.2 (2002): 357-372.

5. Pocock, R. I. “Arachnida.” The Fauna of British India, including Ceylon and Burma. London: Taylor and Francis, 1900. 100-131.

Photo and Video Links:
1. https://www.flickr.com/photos/slopjop/1307601869/

2. http://bugguide.net/node/view/341893

3. https://www.youtube.com/watch?v=nNnKzoQwdAc

What You Didn’t Want to Know About Part I: What the HELL are These Things?! – Amblypygids

We all know (or hopefully we do) that spiders and scorpions are arachnids – arthropods with eight legs belonging to the class Arachnida – but let’s talk about some of the stranger members of this taxonomic group you’ve probably never heard of. Amblypygi, Thelyphonida (the Uropigids), and Ricinulei. What are those?! To be perfectly frank and scientific here, all of these orders are hella weird. Let’s start with Amblypygi.
What happens when you combine a scorpion, a spider, a mantis, and your worst nightmares?

Heterophrynus sp.

You get this gorgeous fellow! Amblypygid means “blunt butt” because these arachnids have no tails, unlike the one we’ll get to in the next part. They are commonly called whip spiders, tailless whip scorpions, or “that thing that Mad-Eye Moody (actually Barty Crouch Junior disguised with Polyjuice Potion – spoilers!) demonstrated the unforgivable curses on in Harry Potter and the Goblet of Fire”, all of which are much easier to pronounce than amblypygid. With leg spans easily reaching over a foot in some species, Amblypygi are the world’s largest living arachnids. Despite their fearsome appearance and movie monster like habits of hanging out in dark places and mainly emerging at night, they are completely harmless to humans. The worst you can get from one of these guys is a minor rose thorn prick from their pedipalp spines and a good scare (and this is if you really push their buttons). Personally, I don’t find them scary at all, but I’m sure a lot of people do. You can actually get them as pets if you’re that weird. Thankfully for my family, I’m not that weird (maybe).
Whip spiders inhabit tropical and sub-tropical regions where their flattened bodies make it easy to sit under bark, under rocks, and in all other stereotypical creepy crawly hiding places. Some are even found in caves and like to hang from the walls or ceiling with their footpads, or pulvilli. At night, they will come out to hunt and get it on with other whip spiders. When this happens, some form of courtship ritual occurs which differs across genera. The male whip spider then backs up toward the female and places a spermatophore (a capsule of sperm) on the ground in front of her before turning to face her again. He entices her to step forward over the spermatophore and take the sperm into her genital opening. After this process the sexes separate and the female later lays eggs into an egg sac under her abdomen. The babies that hatch will ride on her back until after the first molt when they are ready to move around on their own. Tough luck if they accidentally fall off before this, though, because they get no help whatsoever to climb back on and will surely die.


Whip spider babies, like most other arachnids, are miniature versions of the adults. These animals have an unusual first pair of legs. They are so ridiculously elongated and multisegmented that they have taken on the role of antennae and are no longer used for walking. The antenniform legs are held out in front of the animal to help it with navigation and prey location. These “whips” are what give this arachnid its common names. Cave dwelling species often possess even longer legs and some lose their pigmentation and have a reduction or loss of eyes. Amblypygids weren’t even described until the first one was found by Linnaeus in 1758. Up until the mid-1800s, very few more species were named and the number of species fluctuated greatly in the 1890s. Today, there are 136 separate species described with the prediction that this number will climb as the different genera are examined further.

Perhaps the most interesting thing about amblypygids is that some species are social and regularly aggregate in small to large groups. Occasionally this will occur in an outhouse, much to the dismay of anyone needing to use it. In 2006, a study was conducted at Cornell University’s Department of Entomology by Linda Raynor and Lisa Anne Taylor on social interactions in two species of amblypygid, Phrynus marginemaculatus and Damon diadema. What they found was actually pretty sweet… for an arachnid. For the first four months of their lives, both species in the study stayed close to their mother and oriented toward her. She would actively seek them out, settle herself in the middle of the group, and proceed to stroke her children gently with her whips for several minutes at a time. The babies would return this gesture. One female P. marginemaculatus had several groups of babies scattered through the enclosure and visited each of them. Young amblygygids would also show this amicable interaction with their siblings until reaching sexual maturity. Siblings approached each other and greeted each other directly by repeated stroking of their whips. The only signs of aggression ever seen during this time were very mild. Sometimes if an individual entered a tight group of other amblypygids, the members of the aggregation would show a slight threat display by opening their pedipalps. This was very brief, however, and soon led to stroking of the new individual. When a threatening disturbance occurred, young amblypygids would rapidly group together around their mother, often running underneath her. When the researchers put their hands into the cage to transfer a female and her offspring to a new one, she ferociously (and effectively) defended them by trying to stab the offending hand with her palp spines. In contrast, a hilariously ineffective attempt to arouse antipredatory behavior in the amblypygids (to test whether safety in numbers may be a reason for aggregation) involved the researchers placing an anole lizard in their cage. Neither species was perturbed by this and contrarily approached the lizard and explored every inch of it with their whips. Even a tiny, yearling P. marginemaculatus walked right up to it, stroked it for about five minutes, and then calmly walked away.

amblypygids and anole
Say what you will about amblypygids, but you have to admit that they’re, at the least, interesting animals. They give us a great example of the wide range of adaptations that arachnids possess and the variety of appearances they can take on, even if that appears to be a purposeful combination of the creepiest invertebrates on earth. Amblypygids, strange as they are, deserve to be loved and appreciated as much as any other animal does. I’m happy if this article brought even one person reading it a little further away from the disgust and fear that may have been felt in response to the first picture.

1. Harvey, Mark S. Catalogue of the smaller arachnid orders of the World: Amblypygi, Uropygi, Schizomida, Palpigradi, Ricinulei and Solifugae. CSIRO publishing, 2003.

2. Harvey, Mark S. “The neglected cousins: what do we know about the smaller arachnid orders?.” Journal of Arachnology 30.2 (2002): 357-372.

3. Pocock, R. I. “Arachnida.” The Fauna of British India, including Ceylon and Burma. London: Taylor and Francis, 1900. 100-131.

4. Rayor, Linda S., and Lisa Anne Taylor. “Social behavior in amblypygids, and a reassessment of arachnid social patterns.” Journal of Arachnology 34.2 (2006): 399-421.

Photo and Video Links:





Eight-legged, Bouncing Ball of Cute! – Peacock Jumping Spider

Peacock spiders of the genus Maratus are tiny jumping spiders barely four millimeters in length that are endemic to Australia. 53 species of Maratus spiders have been named as of 2015, 20 of which were recently discovered by researcher Jürgen Otto and his team. Though extremely small, these little jumping spiders make up for it with their spectacular colors and mating dances. It’s the males who are really the stars of the show. Females are all dull brown in color and don’t perform any sort of courtship display. They just watch and judge as the little males strut their stuff, trying to win some love.


M. volans.

Males are equipped with elongated third legs which they wave and vibrate in accompaniment with their dance. The back of the abdomen is covered with a flap (which I like to refer to as the “butt flap”) containing brightly colored scales that form special patterns in separate species. These are held up over their heads like miniature peacock tails as they dance around in front of their potential mates. As a male dances, he slowly and cautiously approaches the female and gently places his front legs on her head. If he’s lucky, he will get to mate with her. If not, he must get away quickly to avoid being eaten. These displays can last anywhere from 20 minutes to over an hour!
Just recently, three new specie, M. jactatus, M. sceletus, and M. elephans were discovered. M. jactatus has been affectionately nicknamed “Sparklemuffin” by the graduate student who discovered it.


M. sceletus (Skeletorus).

Peacock spiders have also been known as “flying” spiders because of their special flaps. This was because they were first falsely thought to use these flaps as wings to glide through the air, much like a flying squirrel. However, it has since been observed that they engage in no such behavior. When they jump, their flaps have no significant effects on their speed or trajectory. In fact, courtship is the only activity where these flaps are unfolded. One species, M. vespertilio, is an exception and displays his fan while sparring with other males. None of the other species have shown these male to male contests yet and this behavior was discovered accidentally while filming was taking place.


M. vespertilio males facing off.

These spiders are a perfect example of all the bizarre and amazing creature that we still haven’t found. It is amazing that something so tiny possesses such complex, fascinating, and adorable behavior. Until peacock spiders were observed, scientists had no idea that spiders displayed to each other like this. This just goes to show that there will always be more to learn and every tiny creature that we find is worth protecting. Continue reading

Arizona Bark Scorpion

The Arizona Bark Scorpion (Centruroides sculpturatus) is a tiny scorpion found in, well, Arizona (though it also occurs in other states of the American Southwest as well as Northern Mexico). It lives in the Sonoran desert and is mostly active at night when it hunts crickets, beetles, and other small insects which it ambushes from a dug out burrow. This little guy only reaches a maximum length of about three inches and is very light brown in color. During the day, it hides in the shade or buries itself in sand to avoid the sunlight. It’s often found under rocks, in crevices, bark, leaf litter, and can sometimes find its way into dark places in houses or shoes. During the winter, many bark scorpions will come together to form packs. This is extremely unusual as almost all other species of scorpion are strictly solitary.

As with all scorpions, the Arizona bark scorpion fluoresces when exposed to ultra violet light. They are easy to locate wandering around at night in the desert because of this.

Bark scorpions live for about six years and are sexually mature after one. Females give birth to live young instead of laying eggs. The baby scorpions are exact miniatures of the adult and stay with the mother scorpion, riding around on her back, until their first molt. Litter sizes can range from twenty five to thirty five babies.

Proud mama!

This scorpion is not generally aggressive, but it will become so if it feels threatened as with any wild animal. Its first instinct is to get away, but if that fails, it can deliver a sting that is very painful and can be quite dangerous. Although not normally fatal, stings can lead to temporary paralysis and possibly convulsions on whatever portion of the body was stung. The Arizona bark is the most venomous scorpion in North America and stings should always be treated as a medical emergency and receive adequate medical attention. Stings have been described by victims as feeling like continuous jolts of electricity after envenomation. Luckily, this is such a common species that antivenom is widely available to people who get stung.
If you ever happen to run across an Arizona bark scorpion, don’t mess with it or kill it, just whip out your black light (which I’m sure all of you have and carry around with you at all times, right?), stand back and enjoy it. Scorpions are very interesting and unique arachnids and should be treated with the respect they deserve.

1.McWest, Kari J. “Centruroides Sculpturatus.” Species Centruroides Sculpturatus. Iowa State University Department of Entomology, 26 Mar. 2006. Web. 02 May 2015. .

2.”Arizona Bark Scorpion.” Scorpion Facts and Information. Bio Expedition, 2013. Web. 02 May 2015. .

3.Curry, Steven C., et al. “Envenomation by the scorpion Centruroides sculpturatus.” Clinical Toxicology 21.4-5 (1983): 417-449.

4.Gaffin, Douglas D., et al. “Scorpion fluorescence and reaction to light.” Animal Behaviour 83.2 (2012): 429-436.

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Antilles Pinktoe Tarantula

A lot of people really hate spiders and I think that’s a shame. Yes, they have eight legs and eight eyes which is a little weird, some of them are deadly, and they like to put their webs up right at face level so you’ll accidentally walk straight into them. But there’s more to spiders than that. Most of them aren’t harmful at all and help keep us safe from creatures that actually are very dangerous. Their ability to weave such perfect, intricate works of art in minutes made out of stuff stronger than steel is an incredible feat. Jumping spiders possess some of the most advanced eyes in the animal kingdom and can target things with pinpoint accuracy. Plus, they’re pretty adorable:

Phidippus regius female.

But I’m not talking about jumping spiders or orb weavers today. I’m talking about a gigantic tree spider called the Antilles pinktoe (Avicularia versicolor). This tarantula is a popular pet because it has such beautiful colors and is relatively easy to keep.


Adult spider in a tree by Thomas Baillieaux on Flickr.

Antilles pinktoes are native to the islands of Guadeloupe and Martinique in the Caribbean Sea where they live high in the trees in funnel webs that they spin. They seldom come down to the ground, so when kept in captivity, the height of the cage is more important than their floorspace. They also live in a very warm and humid environment and prefer temperatures in the 70s with 80% humidity and good ventilation.
Pinktoes are very quick, agile, and are very good jumpers despite the fact that they are tarantulas and not jumping spiders. They can easily leap up to a foot straight in the air or out from a perch. When hunting, they will use these skills to creep up and pounce on insects such as crickets, beetles, cockroaches, and moths. Pinktoes will sometimes even take small lizards like anoles.
Female spiders are slightly larger than the males and can grow to have a leg span of up to 6 inches across. The males are not as bulky and usually have more vivid coloration. Males only live up to 5 years whereas females can live over 10 with good care. In the wild, these spiders will group together to form colonies, but this is not the case in captivity, especially not with males and females together. That usually leads to the male being eaten.
The babies, or “sling”, are a very different color from adults, but equally as stunning. When they hatch, they are a beautiful, shimmering blue and keep this color until they start nearing adulthood.

Metallic blue baby!

Although very docile, these spiders don’t like to be handled much. They rarely bite and the bite is no worse than a bee sting when they do, but they also have urticating hairs as with all tarantulas. Instead of kicking them off with their back legs, however, they prefer to press them against the surface of the thing that they feel is threatening. The hairs can be very irritating and cause lots of itching and redness, so it’s best not to annoy the spider too much.
If you’ve ever felt like getting a pet spider, this is a lovely one to have. Just make sure you take good care of it because it’s definitely worth keeping around!

1.Gurley, Russ. “Antilles Pink Toe Tarantula.” Animal World. Animal-World, n.d. Web. 02 May 2015. <http://animal-world.com/encyclo/reptiles/spiders/AntillesPinktoedTreeSpider.php&gt;.

2.Bertani, Rogerio. “Release of urticating hairs by Avicularia versicolor (Walckenaer, 1837)(Araneae, Theraphosidae).” Bull. Soc. ent. Fr 44 (2003): 29-92.

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