Glokar is mostly correct. On a very technical level, only Tigers. Wolves, and Bears (grades 1-3) are Cub Scouts. Webelos (grades 4-5, unless you're in an LDS unit and then it's just 4th grade) are part of a Cub Scout Pack, but no longer "Cubs". Bobcat is not a full rank, per se, but something you earn when you show you know the basics of Cub Scouts, like the motto, slogan, handshake, etc. Boys can join a Boy Scout troop, when they're 11 or 10 and have completed the 5th grade or earned the Arrow of Light Award.