The Devouring Maggot is part of the Northrend Safari achievement. You can find and capture this pet in Howling Fjord but when it is added to your book it does not have a quality color. If you click on it, the name shows blank in the book and has a squirrel picture. The Northrend Safari achievement does not update with credit for the achievement.
Phearia wrote:I just finished Northrend Safari, and, though I didn't have a Devoring Maggot, I still got the achievement. Devouring Maggot is checked as though I have it, but I don't.
Yep it's under known bugs with a few others (crimson moth, wharf rat, some Pandaria ones) that you don't need to get the bugged ones to get the safari ach. Just a shame with the EK version there's the screwed up vendor issues too or it's be doable.