Rat-tailed maggots are the larvae of certain species of hoverflies belonging to the tribes Eristalini and Sericomyiini. A characteristic feature of rat-tailed maggots is a tube-like, telescoping breathing siphon located at its posterior end. This acts like a snorkel, allowing the larva to breathe air while submerged. he most commonly encountered rat-tailed maggot is the larva of the drone fly, Eristalis tenax. It lives in stagnant, oxygen-deprived water, with a high organic content. It is fairly tolerant of pollution and can live in sewage lagoons and cesspools.