In Harry Potter and the Chamber of Secrets, the giant spider colony's leader is Aragog.
Aragog is an Acromantula, a giant, intelligent spider, who lives in the Forbidden Forest with his colony. Hagrid raised him when Hagrid was a student, but Aragog was blamed for the attacks associated with the Chamber of Secrets and was forced to flee Hogwarts.
Harry and Ron find Aragog while investigating the legend of the Chamber. Aragog tells them that the creature responsible for the original attacks was not a spider, but he refuses to identify it. His children then attack the boys before Arthur Weasley's enchanted car rescues them.
Aragog's name is sometimes confused with other magical creatures in the films. Norbert is Hagrid's dragon, Buckbeak is a hippogriff, and Fang is Hagrid's dog. Aragog later dies of old age, and his funeral appears in Half-Blood Prince.