These organisms also have a cephalothorax, which is a fused head and thoracic region. Organisms that fall in the the group Chicerata are the horseshoe crabs, spiders, ticks, and mites. The other sub-phylums are Crustacea and Uniramia. This includes the crabs, centipedes, millipedes, and insects. In our lab we got to dissect a crab.
Insects are the first flyers to appear too.