One of the lords of Hell in
Faust Eric, Earl Beezlemoth was astonished to find out what humans could dream up to do to each other. "I thought we were supposed to be the ghastly ones," he said, his voice filled with awe..
This is clearly a theme close to Pratchett's heart. In Good Omens, Crowley feels that Hell could learn a lot from humans, specifically their computer warranty agreements (a copy of which he sent to the Immortal Soul department with a note saying "Learn, guys").
Beezlemoth is an obvious parody of Roundworld Beelzebub, also known as "Lord of the Flies". Hence the moth part of the name.