puparium

A puparium is a rigid outer shell formed from the hardened larval skin that encloses the pupa of certain insects, most notably flies. This protective casing is a characteristic feature of flies within the Cyclorrhapha group, which have maggots as larvae. The puparium provides an additional layer of defense for the pupa during its transformation from larva to adult. In contrast, other insects like butterflies form a chrysalis, and moths often spin a silk cocoon. The pupal stage itself is a critical period of metamorphosis where larval structures break down and adult features, such as wings, develop.1234