"Maggot" is not a technical term and should not be taken as such; in many standard textbooks of entomology it does not appear in the index at all. In many non-technical texts the term is used for insect larvae in general. Other sources have coined their own definitions; for example: "... The term applies to a grub when all trace of limbs has disappeared ..." and "...Applied to the footless larvae of Diptera."
Maggot-like fly larvae are of wide importance in ecology and medicine; among other roles, various species are prominent in recycling carrion and garbage, attacking crops and foodstuffs, spreading microbial infections, and causing myiasis.