Papilio, papiliones in the plural, means butterfly in Latin. In a military context, the papiliones were the soldiers’ multicoloured tents, perhaps due to the “butterfly-wing” shape they had when laid out on the ground before being pitched. Another hypothesis is that papilio referred to a wing, intended as the side of a larger structure (as in the case of an inscription found in the sanctuary of Diana at Nemi). Perhaps it indicated an open lateral space of a house or a sacred area, which in the Arvals’ sanctuary would have served as a temporary “residence” for the Arval brethren.
The papiliones were part of the Arval complex, now located at Magliana Vecchia, at the foot of the sacred grove of the goddess Dia. Repeatedly mentioned in the records, the acta fratrum Arvalium, the ruins were found during the excavation campaigns carried out by the École française de Rome in 1975 and 198. Today they are no longer visible because the archaeological dig has been backfilled.
They were part of a monumental U-shaped portico facing the balneum or baths, added when the complex was expanded during the Severan age (3rd century AD). Specifically, they corresponded to the rooms behind the curved side of the portico, where the members of the priestly college spent time during the second day of the Ambarvalia festivals. The name might also derive from the tents (papiliones) that sheltered them from the sun and rain.
Reference Bibliography:
J. Scheid, Romulus et ses frères. Le college des Frères Arvales, modèle de culte public dans la des empereurş, EFR 275, Roma 1990
H. Broise, J. Scheid, Tra terra e cielo: la topografia ed il culto del lucus Deae Diae, in Recherches archéologiques à La Magliana, 3. Un bois sacré du Suburbium romain : topographie générale du site ad Deam Diam. Roma Antica 8. Roma: École française de Rome; Soprintendenza Speciale Archeologia Belle Arti Paesaggio di Roma 2020