Claim: Hermit crabs are arachnids.
Evidence: Hermit crabs are decapod crustaceans of the superfamily Paguroidea.
The Decapoda or decapods -LRB- literally `` ten-footed '' -RRB- are an order of crustaceans within the class Malacostraca , including many familiar groups , such as crayfish , crabs , lobsters , prawns , and shrimp.