Why spiders aren't insects

Jeremy at the Voltage Gate explains why spiders aren't insects from a palaeobiological point of view. This is part three in a series of excellent posts on why spiders are not insects. Part one deals with morphology and physiology, while part two details the ancestry of spiders.

*Update 07/16/2007*
Part 4, the last in the series is posted. Jeremy explains the concept of homology and how the molecular phylogeny of spiders is congruent morphology and in fact the horseshoe crab is the closest relative, not in fact insects!

Thanks for the enlightening posts Jeremy!