Prosternum: the fore-breast: the sclerite between the fore-legs.
Prostheca: a mandibular sclerite set with hair, articulated to the basalis - q.v. -and equal to the lacinia of the maxilla.
Protamphibion: a name applied by P. Mayer to the hypothetical common ancestor of the Perlina, Ephemerina and Odonata.
Protandry: the appearance of males earlier in the season than females.
Protarsus: the tarsus of the anterior leg.
Proteiform: having many fortes or varieties: protean.
Protergum: in Odonata, the upper surface of prothorax.
Proterotypes: primary types, including all the material upon which the original description is based.
Prothoracic bristle: in Diptera, a strong bristle immediately above the front coxa: see propleural bristles.
Prothoracic glands: occur in Orthoptera, on the sides of prothorax in certain Phasmid genera.