Moties – The Mote in God’s Eye
As far as classic “let’s meet the aliens” novels go, The Mote in God’s Eye is one of the big ones. The Moties, as they are called by humans, have a genetic caste system, meaning that members of the species are born with a genetic predisposition to excel in a particular field. They also have two right arms and one strong left arm, because of a genetic mutation. Definitely one of the more interesting literary alien races.