bah, everything was bigger back then... scorpions, millipedes, ferns, dragonflys, everything.
take this Sea scorpion for example.
edit: i tried finding pictures of fossils of massive 3 foot long land scorpians or the giant spiders and millipedes, but to no avial.
it seems 6' long spider fossils have been unearthed.
Creepy, huh.