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?
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.
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.
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