Aquavirious Maggot

Aquavirious Maggots are supposedly brain-like creatures that Luna Lovegood and her father believe are being bred in the Department of Mysteries.

Like many of the things Luna and her father believe in, it is unlikely to exist. However, there were brain-like creatures swimming in a tank in the Department of Mysteries when Harry, Ron, Hermione, Neville, Ginny and Luna travel to the Department in 1996. However, this theory was later disproved.

If they do exist, they are likely to be slimey and venomous, and may be similar to a large maggot.

Etymology
Derived from the Latin "aqua" meaning "water", and "virius" meaning "toxin" or "poison". A maggot is the common name for the larval phase of development in insects of the order Diptera (flies).