I don't know if you have found this out yet or not but, on Ischia, DiMeglio is an incredibly common name. I am sure though that considering the size of the families, all the DiMeglios could easily go back to a handful in the 1700's. There do not seem to be many out side Ischia.

My great grandfather was Pasquale DiMeglio born jan 20, 1885 in Ischia. His parents were Vito Nicola DiMeglio and Maria Gioseppe Maniero. On the ship's manifest from Ellis Island it says he is going to a cousin in Chester PA. I could not read the cousin's name and he never made it past Brooklyn.

A cousin who has documents from Ischia promises to go through it this xmas and make me copies. I don't know if this will have additional information.
Valerie