This category is for sites devoted to the largest of all animal phyla, Phylum Arthropoda. This phylum includes the insects, spiders, mites and ticks, crustaceans, centipedes, millipedes, isopods, and trilobites. The arthropods typically share a common body plan. They have an outer tough cuticle and they are divided into segments, each of which may carry jointed appendages. Often there is a head, thorax or trunk and an abdomen. They are an amazingly successful group of creatures and have been around since the Precambrian, 600 million years ago.