Wednesday, 27 December 2017

"The Spirally Slanted Spidrid's Mad Dash For Safety!"

Last September I presented part of a painting showing the Mad Sickle, a species of spirally slanted spidrid ('slanties'). The comments quickly gave rise to two new ideas: the first was that the legs and body of slanties might hook up to form a nearly impregnable wall. I should probably do a painting of one. The second was that slanties might well move by cartwheeling. Imagine that as follows: a spidrid's body along with the legs sticking out in all directions forms a disk; now flip the disc onto its edge and roll it along; that's it.  Slanties might use this trick to escape very quickly down a hill.

As usual, life on earth manages to trump anything the speculative biologist can think of. To prove that, here is a short video showing a Namibian spider using exactly that same trick to escaper down a hill, narrated by Sir David Attenborough. There are also spiders that actually do a series of somersaults, head over tails, but that is another type of movement and also another story: here's a video).

Slanties have an additional trick up their sleeves: once flipped on their side, there is nothing to stop them from using the power of their legs to make this an active way of locomotion. Slanties need not be content with passively rolling downhill; they can get out of the way on horizontal terrain too. Actually, they could even roll uphill. I do not think that that would be more effective than normal walking (normal for slanties, that is!), but they could. 

Mind you, I am not saying I am the first to invent this way of locomotion for a fictive animal. I have written about Warren Fahy's 'disc ant' in the past, and there may be earlier manifestations as well.

So here is a quick animation of a slanted spidrid moving in this fashion. The legs flex and extend while the body rotates. I suppose it could also move on the other direction with nearly the same movement. We are looking at the dorsal side of the beast.

Here it is again, rolling in and out of view.

I doubt the animal would use this type of movement as part of its normal repertoire, because I do not think it would be able to see well, with the entire world circling around them like mad. In this respect, the movement is a bit like 'cernuation', a term to describe the movement of the 'squibbon' of The Future is Wild. To read about possible visual problems, find the posts here and here. The poor spidrid only sees the world as a blur when wheeling around in this way, and that is why it uses wheeling only as a last resort to escape from predation.


Petr said...


Slanties just got a whole lot trippier than they already were. :D

I did know about the first spider, had no idea about the second. Goes to show your blog is a good go to place for learning something new, and I must commend your efforts for keeping this blog alive for such a long time.

I hope you had happy holidays, I wish you lots of luck in the new year, and also success with The Book! :)

Sigmund Nastrazzurro said...

Petr: Thank you. I had a new look at your origami work, and was amazed how well you manage to capture the shapes of animals as odd as euryptids by folding a piece of paper! Fascinating.
Come next April the blog will be 11 years old. The Book now stands at 96 pages. The next paintings will be about tetrapters (renamed from 'tetropters'), so I now have to figure out how to do microscopic scenes without them getting too photorealistic.

Happy new year to you too!

Anonymous said...

>so I now have to figure out how to do microscopic scenes without them getting too photorealistic.
how about..."I could've used a camera, but that feels like cheating; I painted what I could while the tetrapter was near until it flew away - the rest is from memory" (or the last bit could be "i agreed with the tetrapter that that was a good place to stop")

regardless of what you choose, I hope you and your family and the Book have a great New Year! all the best to you.

-Anthony Docimo

Petr said...

Thank you, Gert,
shame to say I haven't really folded much lately. I've got to admit I have a bit of a Eurypterid obsession. They are fascinating to me. Incidentally, they are also part of the reason why I haven't folded recently. I'd love to recreate Pentecopterus as my next project, and I'm still at the drawing board phase months later. Too many spikes to fit in a square of paper. :)

I would like to go back to the brontorusp and fold a larger more accurate version, but I haven't found the right paper yet. You'll be the first to know when I go through with this. It is going to be just a refold of the older model, I don't think it needs any changes in terms of the underlying design, but I hope to be able to improve the shaping and put a lot more detail into the finished piece by starting with a larger sheet. I kind of want to see what a foot-long model of a rusp would like.

Tetrapters are definitely critters I'd love to learn more about, and I don't think photorealism would necessarily be a bad thing here, at least in the sense of allowing us to see tiny critters in detail. I think something like this can illustrate the level of thought you put into the biosphere of Furaha. Many worldbuilders only bother with megafauna. :D

Evan Black said...

When I watch the spidrid spinning, I'm reminded of a perpetual motion machine. Could a spidrid generate a little more forward momentum by sort of "thrusting" legs forward as they swing toward the "front" of the creature? Perhaps some species might develop a node of weight on their limbs to help facilitate this form of transportation?

Sigmund Nastrazzurro said...

Evan: when I designed the animation I had only considered pushing at the ground, involving those legs that are down at any particular moment in the cycle. The only movement I designed for legs at the top concerned an 'in between' movement connecting the end and beginning of pushing againt the ground. I very much like your idea that the top legs contribute to the movement. Folding the legs close to the body would do so as angular momentum is conserved. It also seems to be called the 'ballerina effect'. I found a nice demonstration here:
Mind you, I am hesitant about adding weights to the legs: as you can see in the video, they help. But when the legs need to puch against the ground, they would make it more difficult to accelerate the legs, and they also wouldn't help when the spidrid is walking normally; normally for a slantie, that is ;-)

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Sigmund Nastrazzurro said...

Anonymous: this is not the first time. I one spent quite some time rerporting this to Google, and the offending posts were then deleted. Why would someone fill a website with haphazardly stolen material?