What arthropod class in?

In taxonomy, 'class' has a specific denotation. Arthropoda (the arthropods) is a major division called a phylum. It falls under the animal kingdom (Animalia, or Metazoa) and also falls under other classifications such as Eukaryota, Opisthokonta, Eumetazoa, Bilateria, Protostomia, Ecdysozoa and Panarthropoda.

Below phylum are the subphyla and the classes, of which arthropoda has several, including the Malacostraca class (lobsters, shrimp, etc), the Insecta class (insects), and others.