posted on Jun, 1 2008 @ 12:53 PM
Just to set minds at rest (for those of you who are concerned that one day you might wake up cocooned...)!! There is a very well understood rule in
invertebrate zoology that governs the theoretical maximum size of organisms. In the case of arthropods this maximum comes about, indirectly, because
of the composition of the cuticle (exoskeleton) which is primarily a protein called chitin. As the animals get larger, they also get
disproportionately heavier - imagine the surface area of the animal increasing as a square area (x^2) and the volume increasing a cube function
(x^3).
For a large organism, a chitinous cuticle (hard, tough) would be incredibly heavy. So, large arthropods that need to move fast (think huntsman
spiders...) have thin soft cuticles that are lighter. They maintain positive internal pressure which allows them to move - however, if they are
damaged in any way, they rupture and die due to the delicate exterior and positive internal pressure. Those that retain the thick cuticle are heavy,
slow and non-predatory (e.g. rhinoceros beetles).
Large tarantulas are as big as any arthropod can get unless totally sessile or supported by water - thank f@*ck!! That is, unless these pesky
iranians fabricate them from kevlar, PTFE or some other such superlight tough material :-)
All the best,
N