So I’m reading The Hobbit and Lord Of The Rings, and among the obstacles our heroes have to overcome are a few varieties of giant spiders (Mirkwood spiders, Shelob, etc). This conjured up memories of Arachnophobia (the movie, not the disorder), The Mist (Stephen King short story), Gilligan’s Island, and various other sci-fi stories and movies where people are attacked by AOUSs (Arachnids of unusual size).
Finally, the question:
How big can spiders actually get and still both be viable and be effective predators? Are tarantulas that size just because that’s how big they happen to be? Or is it because that’s the limit on spider size? The giant amazon spiders from Arachnophobia? What problems would have to be overcome for a spider to grow to cat-size or medium-to-large dog-size? I’d assume it would need to have thinner proportions and a thicker exoskeleton than a tarantula, since a fat abdomen would be prone to both crackage and cooling problems at larger sizes.
Whew. Now that that’s over… Ever played Diablo II? If not, there are a couple acts with giant insects. In Act 3, there are these cocoons about the size of cocooned people lying on the forest floor. If you kick them open, out pop about half a dozen spiders the size of beagles, and they slowly scuttle away. They don’t count as monsters because they’re puny and small, compared to their parents, which are the size of Mini Coopers.
Me, if I kicked open a duffle bag and eight spiders the size of beagles crawled out?
I’d need therapy. But the cool part would be that I would have learned how to fly by sheer force of will…
I think crustecians (sp?) like lobsters and crabs are decended from arachnids. Even if they aren’t, they have a similar body structure. That is to say, a hard exoskeleton that protects a soft, multileg interior. So I would imagine that spiders could get at least that big.
The factors that limit a spiders size are probably:
Food. The bigger a spider is, the more it has to eat. It would be hard to build a web big enough to catch children and small dogs.
Physics. Once a shell gets too big, the spider will collapse under its own weight. How big that is, I don’t know. A human is strong enough to walk around with a suit of midevil armor on, so maybe a spider could be at least as big as a human. It definitely couldn’t be as big as Godzilla though.
I’m not particularly afaid of spiders. I actually don’t kill them if I find them in my house because I know they eat other bugs. If I saw one the size of a dog, however, I would freak out like you would not belive.
Not to plug one of my better (if extremely icky) moments in GQ, but the question of arthropod size limitations was discussed quite extensively in the uberroach thread. Spiders and their slightly different respiratory systems are discussed specifically toward the end of the first page.
I believe our general conclusions were: they could conceivably become fairly large–maybe around house cat size–but they would be slow, relatively fragile, and have some difficulty keeping themselves fed. A large tarantula is a surprisingly vulnerable creature; even a short fall can kill it, so you don’t have to worry about big spiders jumping or falling on you too much.
Close. Arachnids more likely descended from lobsters and crabs. All land(and air) animals evolved out of the sea, remember?
Spiders are definitely limited in size by ther exoskeleton. Exoskeletons are not efficient enough of a superstructure in fighting against the force of gravity. Crabs, on the other hand, can get to be huge because their weight is suported by the water.
Ah, yes. I remembered that thread, but couldn’t find it.
What I was thinking was something like this: The spiders would have to be longer and narrower than (for example) a tarantula, maybe like a jumping spider. Narrow legs, narrow body. I’m not talking about the size of a buick…something the size of a giant tortoise or a large dog would be about right for the Mirkwood spiders–big enough to web up a dwarf and fight hand to … um … legs with a hobbit. So we don’t have the uberroach problems, at least not to the same degree.
Do you think something that big would be work? What physiological limitations would prevent it, or make it problematic?
Assuming it’s viable, how would it fare as a predator? Also assume color camouflage, venom, web spinning ability.
Sue, thanks for the links. My GF was pissed because I pulled them up while she was sitting with me. She hates bugs. hahaha