Ptilinum
Definition
An inflatable frontal sac on the newly eclosed adult blow fly, used to burst through the puparial operculum and push through soil. It deflates after emergence and the resulting crease (the ptilinal suture) is visible on the adult head as a permanent scar.
- Location
- Frontal sac on the newly eclosed adult blow fly
- Function
- Bursts the puparial operculum and pushes the fly through soil
- After emergence
- Deflates, leaving a visible ptilinal suture scar
Common questions
Why is the ptilinal suture useful in entomological evidence?+
It is a permanent crease on the adult fly's head confirming that eclosion actually occurred, helping entomologists distinguish a fully emerged adult from one collected still at the larval or pupal stage.
Do all forensically relevant flies have a ptilinum?+
It is characteristic of the Cyclorrhapha group, which includes blow flies, and is used taxonomically to help confirm the life stage and developmental group of specimens collected at a scene.
Related terms
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- A temperature-corrected measure of developmental time. Calculated by summing (hourly ambient temperature minus the species-specific base temperature threshold) across the period of...
- Base Temperature
- The species-specific temperature below which development effectively ceases. For most forensically relevant blow fly species this is in the range of 2-10...
- Instar
- A developmental stage between moults (ecdysis). Blow flies have three larval instars (L1, L2, L3), each ending when the larva sheds its...
- Posterior Spiracles
- The paired breathing openings at the hind end of a blow fly larva. Their slit count and sclerotisation state are the primary...
- Pupariation
- The process by which the third-instar larva contracts and hardens its own cuticle to form the puparial case (puparium) that encloses the...