ptilinum

ptilinum (noun; plural ptilina; Greek ptilon, feather): 1. (Arthropoda: Insecta) In Diptera, a temporary bladderlike structure of a pupa that can be inflated and thrust out through the frontal (ptilinal) suture, just above the bases of the antennae, that pushes off the operculum of the puparium.

2. (NEMATA) Sometimes inappropriately used to describe horn-like or leaf-like ornamentation on the anterior extremity of parasitic forms.