Puparium

Definition

The hardened, sclerotized cuticle of the last larval instar that forms a protective case enclosing the pupa in higher flies (Cyclorrhapha: Diptera). Unlike most holometabolous insects, whose pupae are exposed or protected only by silk or substrate, cyclorrhaphan flies retain the larval exoskeleton, which contracts and hardens into a barrel-shaped puparium. The adult fly emerges by breaking through a predetermined line of weakness at the anterior end (eclosion).

Etymology

From Latin pupa (doll, puppet) + -arium (place or receptacle), referring to the container-like function of the hardened larval skin.

Example

In the Mediterranean fruit fly Ceratitis capitata, the creamy-white third-instar larva contracts into a leathery, barrel-shaped puparium that darkens to reddish-brown; the adult emerges through a circular cap formed by the eversion of the ptilinum.

Synonyms

• caster (fishing bait context)

Related Terms

• pupa
• instar
• Eclosion
• Pharate
• complete metamorphosis
• Cyclorrhapha
• Ptilinum
• Sclerotization

Usage Notes

Puparium is specific to Cyclorrhapha (Schizophora and related groups); other Diptera and holometabolous insects lack this structure. The term is sometimes misapplied to any pupal case, but properly refers only to the modified larval exoskeleton. In angling, 'casters' specifically refers to puparia of blow flies (Calliphoridae) used as bait. The plural puparia follows Latin neuter second declension; 'pupariums' is nonstandard.