A maggot here does not mean a flesh-eating scavanger. Maggot was used in its now obsolete sense of a caprice. In the early 18th century it was the custom to apply the term to dance tunes and to others, such as this, of a whimsical character. Maggot could also be a man who is a jack of all trades.
Notations from The Life and Times of an Irish Harper by O'Donal