Question for the biology guys and gals

Spiders can only grow so large (on Earth) due to the pressure of gravity on their exoskeletons, right? Which is presumably why we don't have giant spiders running around terrorizing the countryside. But is it biologically possible for an ENDOskeletal "spider" to exist here? A creature with eight muscular legs -- maybe one that uses a sticky natural filament to make traps in caves and stuff? Feasible or no? 

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  1. Very cool, Kelvin. Thanks for the linkage.

  2. You might want to check out this blog as well: http://planetfuraha.blogspot.com/2011/05/how-many-legs-are-best-for-megamonsters.html

  3. Kelvin's right, but that's not the whole story. The square cube law has serious implications on the efficiency of arthopodal circulatory systems (they by are large work by simple diffusion). At times in the earth's history where oxygen tensions in the atmosphere were higher, arthopods grew larger.

  4. And they can still get pretty darn big, just not big-as-a-horse big.

  5. Spider limbs don't move exclusively by muscle action, there's a hydraulic component to their movements.

    As if they weren't terrifying enough.