Maggots are various types of flies that are in the larval stage of development. There are four stages of a fly's life cycle: the egg stage, larval stage, pupa stage and adult stage. The average life span of a fly is between 15 and 30 days.
In a similar way to caterpillars and butterflies, maggots begin their lives as larvae and transform over a period of about four days into flies. A fly's larval phase actually consists of three sub-phases: the first-, second- and third-instar phases. Over these three phases, larvae turn from a white color to a reddish brown and shed multiples times until they form cases around themselves in order to pupate.