Rat-tailed maggot larvae develop through three stages, all of which have the caudal projection with a small pair of spiracles at the tip.
The third stage larva is about 23mm long and 15mm wide, with eight pairs of ventral swellings (pseudopods). There is a pair of short, dark anterior spiracles.
The maggot moves to drier areas to pupate. The pupae are grey-brown and have a pair of horn-like anterior spiracles as well as the caudal projection.
The life cycle from egg to adult is about 30 days in the summer, with the larval stages lasting about 18 days and the pupal stage about 10 days.